ISSN
Be STAR NEWSLETTER
NUMBER June
Editor in Chief Technical Editor
Geraldine J Peters Douglas R Gies
e mail g jp eters mucen usc edu e mail gies chara gsu edu
Space Sciences Center Center for High Angular Resolution Astronomy
University of Southern California Department of Physics and Astronomy
University Park Georgia State University
Los Angeles CA Atlanta Georgia
Tel Tel
FAX FAX
Be Star Newsletter
Contents
Editorial G Peters
Working Group Matters
Working Group News Dietrich Baade
Minutes of the WG Meeting at the IAU GA Petr Harmanec
Alicante Conference June July Myron Smith
Contributions
Mu Cen the ticking and ringing of a star Th Rivinius D Baade S
Ste O Stahl B Wolf and A Kaufer
A Multi Wavelength Campaign on Gamma Cas I I Circumstellar
Structures Inferred from Ultraviolet Continuum and Si IV Line Varia
tions Myron A Smith
Stellar wind variability of the Be star FY CMa H Cao and J Dachs
Energy Crisis in Be star Radiation Emission Krishna M V Apparao
What s Happ ening
Discovery of p erio dic brightenings in the B variable HD P
Harmanec
A Painting of the Be sdO Binary Phi Persei D R Gies
Interferometric Results Highlighted on WWW Site Philipp e Stee
Atlas of Sp ectrop olarimetric Observations of Be Stars Karen Bjorkman
Abstracts
Bibliography
Meetings
LaTeX Template for Abstracts
The Be Star Newsletter is produced at and nancial ly supported by
the Georgia State University Department of Physics and Astronomy
The electronic version is available on
the World Wide Web http www chara gsu edu BeNews intro html
or by anonymous ftp ftp chara gsu edu cd BeNews
Be Star Newsletter
EDITORIAL
An appropriate theme for this Issue No of the Be Star Newsletter might b e New
Faces for Old Friends Consider for example Cen discovered to have Balmer
emission almost years ago by W P Fleming For the past two decades it has b een
trying to reestablish its former prominent circumstellar CS envelope apparently
through a series of quasi p erio dic mini outbursts Now researchers show that these
outbursts apparently coincide with the maxima from the constructive interference of
at least four of six coherent NRP p erio ds in the star NRP and the mini outbursts
that are slowly pro ducing another prominent CS envelope app ear to b e linked
Another familiar face is that of Cas or do we know this star It was the rst Be
star to b e discovered more than years ago by A Secchi but has not endured as
a prototype for a classical Be star esp ecially in view of its unusually strong X ray
emission In this issue new data from the IUE spacecraft are presented that lend
further supp ort to a prior conclusion that the star has a magnetosphere that may
pro duce it s X ray emission Contributions on b oth Cas Cen follow earlier
rep orts in the last issue of the Newsletter
In WHAT S HAPPENING we include a rep ort on the new mo del for the interacting
binary Be star Per that emerged from recent HST observations What a change
from the mo del some of us advocated at the Cap e Co d meeting in But the
consensus is still that mass transfer spun up the Be star But the new revelation
is that the secondary is indeed a hot O type sub dwarf suggested earlier by several
researchers that is the remnant of a more massive star that transferred its material to
the Be star Indeed a newly con rmed face for this Be star Also in this issue of the
Newsletter are contributions on the variable mass infall in FY CMa and the energy
budget in Be stars a rep ort from the new Chair of the Working Group on Active B
Stars minutes from the WG meeting held at the IAU GA in Kyoto a prosp ectus for
the prop osed meeting on the Be phenomenon in Alicante Spain in abstracts
of new pap ers the newly expanded bibliography and information on forthcoming
meetings of interest to the active star community
Beginning with items received for the next issue of the Newsletter we plan to adopt
a new publication pro cedure in order to communicate with the community in a more
timely fashion Contributions including abstracts meeting announcements will
b e p osted on our web site shortly after they are received and undergone review by
the editors In fact we have already b een doing this on an exp erimental basis have
you noticed So please make a b o okmark in your web browser and check our web
edition often At irregular intervals usually twice p er year we will collect all material
received since the last issue pro duce a bibliography and publish a pap er copy We
will still o er a p ostscript le of the entire issue This pro cedure will allow us to
alleviate a p erennial problem that items received just after an issue comes out are
old news by the time the next issue is published Please let us know if you approve
of the new approach
We urge those who are receiving the pap er edition of the Newsletter to inform us of
address changes as so on as p ossible With each mailing we have a signi cant number
of returns that increase our cost of distributing the pap er copies
Be Star Newsletter
Contributions abstracts for Issue should b e received by
November
Send contributions by Electronic Mail to
g jp eters mucen usc edu and gies chara gsu edu
either as LaTex or p ostscript les We are now requiring that abstracts b e submitted
as LaTex les using the template provided in this issue it can also b e downloaded
from our web site Illustrations should b e sent by E mail as p ostscript les If it is
not p ossible to transmit your contribution electronically please send or fax
a dark camera ready copy
We would like to thank those who contributed to this issue It is your input that
keeps the Newsletter b oth interesting and useful to the active B star community and
we lo ok forward to receiving your contributions for Issue No
We appreciate the continuing supp ort from the Department of Physics Astronomy
at Georgia State University for the pro duction of the pap er edition of the Newsletter
Gerrie Peters Editor in Chief
Be Star Newsletter
WORKING GROUP MATTERS
Working Group News
Some months ago the Working Group on Active B Stars completed another three
year IAU activity cycle This also implied changes in the comp osition of committees
In the case of our Working Group Petr Harmanec Myron Smith and Rens Waters
reached the end of their resp ective second term and therefore left the Organizing
Committee OC Katy Garmany served as a member of the OC on b ehalf of our
sp onsoring Commission Stellar Classi cation We thank all four of them for the
work they have done for the Working Group
In his last e mail as the Chairman of the Working Group Myron Smith has already
informed all members ab out the new comp osition of the OC But for go o d order s
sake let me rep eat it here D Baade chair J Bjorkman J Cassinelli D Gies H
Henrichs M Marlb orough V Niemela A Okazaki G Peters NL editor nonvoting
M Smith outgoing chair nonvoting and S Ste As the new chairman I cordially
welcome the new members Jon Bjorkman Virpi Niemela on b ehalf of Commission
Atsuo Okazaki and Stanislav Ste and congratulate them on their election
Myron Smith deserves our sp ecial thanks as an unusually active chairman of the
Active B Star Working Group As is b eing rep orted elsewhere in this issue of the
Newsletter his e orts will come into full fruition with the Alicante meeting in
Several OC members also serve on the Scienti c Organizing Committee SOC which
has furthermore kindly granted the chairman of the OC active observer status There
fore the meeting should serve the interests of the Working Group members and their
research actively and well It will undoubtedly guide and inspire our work into the
next century
Unfortunately only few members of the Working Group could attend the IAU General
Assembly in Kyoto and if so in many cases only partly Therefore only a very limited
meeting could take place in Kyoto It was very kindly organized and chaired by John
Percy A summary by Petr Harmanec is included in this issue of the Newsletter I
thank b oth of them for their supp ort
I wish to extend the Working Group s gratitude also to Gerrie Peters and Doug Gies
for their constant successful e orts to edit pro duce and distribute this Newsletter
It is an imp ortant vehicle for the exchange of information within the Working Group
and thereby provides the essential glue for the cohesion of the Working Group Not
only have Gerrie and Doug provided this community service already for many years
but they have also kindly agreed to continue with it thank you
In this p erio d of rapidly changing communication to ols and information carriers our
Working Group to o has to monitor these developments and check the needs for
adaptation One obvious idea that has b een oating around for quite some time now
is to supplement the printed copies by electronic means esp ecially the Worldwide
Web Such a solution would save cost and make news accessible more quickly For
instance all contributions could within days after receipt by the editor b e p osted on
the Web p erhaps also using an e mail noti cation system for subscrib ers A printed
version would then only b e issued at irregular intervals and when there is su cient
Be Star Newsletter
material I invite the Working Group members to communicate their views on this
matter to me In particular we would need one or more volunteers who would b e
willing to maintain the necessary home page
Dietrich Baade
dbaade eso org
WG Meeting at the IAU
Minutes of the meeting of the Working Group on Active B Stars held on
August during the rd General Assembly of the IAU
The rd General Assembly in Kyoto was attended by more than registered par
ticipants and it was necessary to schedule many parallel sessions Very unfortunately
this also led to only a limited attendance of the Working Group meeting There was
a similar problem with many of the other business sessions and this was called to
the attention of the IAU Executive Committee Yet p eople like Dr M Jerzykiewicz
the newly elected president of Division V were present
The meeting was chaired by Dr John R Percy who rst announced the newly elected
members of the organizing committee of the WG Drs J Bjorkman V Niemela
A Okazaki and S Ste and rep orted that Drs K Garmany P Harmanec M Smith
and R Waters are leaving the committee after serving for two consecutive p erio ds
They were thanked for their service to the WG Dr Dietrich Baade has b een elected
as the new chairman to replace Dr M A Smith
Then the plans to have another large international conference devoted to active B
stars were discussed at some length Since Hungarian colleagues plan to organize
a meeting on stellar pulsations in Budap est b etween August and to
celebrate the one hundredth year anniversary of the Konkoly Observatory and to
allow witnessing a total solar eclipse during the meeting there was a prop osal to
have the B star meeting to b e held in Alicante Spain in a week b efore or after the
Budap est meeting However it was stressed that the Budap est meeting will mainly
b e fo cused on late type Cepheids and RR Lyr stars Moreover Dr Fabregat the
chairman of the provisional Lo cal Organizing Committee of the planned Alicante
meeting announced that the Congress hall will only b e available in June and July
but not in August Furthermore the weather is hot and the city is crowded in
August The ma jority opinion then was to hold the meeting in June as originally
recommended by the Spanish hosts
Some discussion to ok place on the three tentative titles of the meeting suggested by
the Scienti c Organizing Committee The title OB Stars and the Be phenomenon
was considered to b e the most appropriate one by most of the participants It was
also recommended that the SOC should try to contact the colleagues who regularly
organize meetings on mass loss from luminous stars and co ordinate the program of
the meeting with their plans
The next topic was the Be Newsletter Dr P Harmanec reminded that the suggestion
of the organizing committee of the WG which met in Juan les Pins in was to
replace the printed Newsletter by an electronic b oard with an automatic circulation of
Be Star Newsletter
the news calls for observations etc He expressed the opinion that the Be Newsletter
is sometimes b eing misused for cheap unrefereed publishing His opinion was partly
opp osed by Dr J Percy who agreed with the idea of an electronic b oard but expressed
his b elief that the printed Newsletter is still very helpful to colleagues who do not have
an easy access to Internet No further discussion followed and no recommendation was
accepted on this matter though there was sympathy for keeping the pap er edition
The meeting then discussed the idea of having an electronic bulletin b oard for time
dep endent information such as unusual b ehaviour of stars and observing campaigns
Dr Conny Aerts agreed to conduct this bulletin b oard as long as it did not develop
into a discussion or chat group
Several brief scienti c presentations followed Dr P Harmanec rep orted ab out the
systematic UBV monitoring of bright Be stars at Hvar A summary rep ort on these
observations will so on app ear in press Pavlovski Harmanec Bo zi c et al
A AS This pap er also contains references to all earlier studies based
on Hvar photometry In two other pap ers Harmanec Pavlovski Bo zi c et al
Journal of Astronomical Data Harmanec and Horn Journal of Astronomical
Data the original observations complete data archives and software for the data
reduction and retrieval will b e published
Then Dr J Percy rep orted on his program of UBV monitoring of Be stars which
includes Toronto observations observations secured with the Pho enix Automatic
Photo electric Telescope and observations obtained by the AAVSO photo electric pho
tometry program The results are in press Percy et al PASP The data are to
b e dep osited in the IAU Archives of unpublished observations As a rule the same
comparison and check stars as those recommended for the international campaign
and used at Hvar were usually adopted
These two large data sets in combination with the long term monitoring program
organized by C Sterken at ESO represent a substantial increase of our knowledge
ab out the light and colour b ehaviour of bright Be stars on various time scales
In a comment to this Dr M Jerzykiewicz o ered his unpublished UBV observations
of ES Vul
Finally Dr N G Bo chkarev rep orted on o cassional optical ares of V Cyg the
optical counterpart of the well known X ray source Cyg X Some doubts were raised
on the reality of this phenomena but Dr P Harmanec rep orted that the Hvar data
also show similar brightenings for some more normal Be binaries without a known
X ray secondary in the system
P Harmanec Secretary Internet hec sunstel asu cas cz
Astronomical Institute Academy of Sciences of the Czech Republic Ond rejov
Czech Republic
Be Star Newsletter
Prop osed Alicante Conference
TITLE The Be Phenomenon in Early Type Stars
DATE June July
VENUE Conference Hall of the Ca ja de Ahorros del Mediterraneo Alicante Spain
SPONSORING INSTITUTIONS University of Valencia University of Alicante Ca ja
de Ahorros del Mediterraneo CAM
PROPOSING IAU COMMISSIONS requested
Variable Stars
Stellar Photometry Polarimetry
Stellar Sp ectra
Close Binaries
Space High Energy Astrophysics
THE SCIENTIFIC ORGANIZING COMMITTEE SOC
Balona L South Africa
Bjorkman J United States
Fabregat J Spain
Fullerton A Canada
Hummel W Germany
Kambe E Japan
Marlb orough M Canada
Mennickent R Chile
Ro che P United Kingdom
Smith M United States Chair
Ste S Czech Republic
Six of these members were initially prop osed by the IAU Working Group on Active
B Stars Chair D Baade the remainder were elected by the initially selected SOC
Criteria used in this election included recent refereed publications in the eld of Be
stars and geographical distribution We note that the ma jority of the SOC are young
astronomers with half of them having b een in graduate school a decade ago
The title for the conference was the result from many discussions within the Working
Group WG on Active B Stars the WG s OC and the SOC
LOCAL ORGANIZING COMMITTEE
J Fabregat Chair J Berna G Bernab eu E Enjuto J Perez Ortiz
The LOC members are members of the two sp onsoring universities
Be Star Newsletter
DETAILS OF THE PROPOSED CONFERENCE
The Venue
In the Universities of Alicante and Valencia extended an invitation to the Or
ganizing Committee of the Working Group on Active B Stars to hold a conference
in Valencia Spain It is easy to understand why the prop osed venue was readily
accepted by the Organizing Committee Alicante is an a ordable site for Asian and
North American as well as Europ ean participants It is b oth a tourist and university
city which o ers a variety of natural and cultural attractions for visitors Moreover
it is appropriate to salute the longstanding observational work on Be stars by as
tronomers at two sp onsoring institutions and thirdly to acknowledge the expanding
role of Spain in providing mo dern astronomical observing sites in Europ e which are
well equipp ed for studies of variable stars and galaxies
Accommodation and other costs
The LOC is currently in the pro cess of searching for funding to defray the exp enses
of some conference participants particularly those astronomers who are young must
travel far or come from developing countries The registration fee is exp ected to b e
ab out This price includes the cost of publishing the pro ceedings
Accommo dations include dormitory housing night approx with shared baths
and hotels The following are estimates of hotel ro om rates in Alicante available to
the participants
Single Ro om Double Ro om
The hotel ro oms are equipp ed with bathro oms and TV The CAM conference hall
itself is in the center of Alicante and has a large auditorium which is equipp ed with
audiovisual facilities
The Date and Duration of the meeting
The choice of late June was dictated by the availability of the conference center the
University of Alicante s academic schedule and the lo cal tourist season Late June
is a time when the spring academic semester is nearing completion and university
dormitories are still op en for rental of available and economical ro oms During this
time the average temp erature is still rising so the tourist in ux with attendant
higher hotel costs will have not yet started This time also assures that the home
obligations of most conference participants who have university jobs will b e ended
The conference is planned for days
Structure of the Meeting
The structure of the meeting will b e in a conventional dual format of oral talks and
p oster presentations which will run eight hours including co ee breaks p er day The
oral presentations will b e a series of review summaries and invited talks dominated by
the work of one or two groups of a series of sub elds p ertaining to the main sub ject of
the Be phenomenon An attempt will b e made in the oral talks to weave ndings from
relevant p oster pap ers into the presentation In addition there are many arguments
circulating within the Be scienti c community so adequate time will b e set aside for
discussion following ma jor talks Time will b e provided for p ersonal reconnaissance
Be Star Newsletter
of the p osters every day and two sessions of summaries of p oster pap ers which will
b e followed by short group discussion The conference will b e ended with a short
summary by the Chair and by a discussion of future research directions needed for
the eld
Dedication
The meeting will b e dedicated to the works of Dr Arne Slettebak and Mercedes
Jaschek
Dr Slettebak is currently semi retired For more than three decades he led a research
group devoted to the observations of Be stars and to the role rotation and other
p ossible physical pro cess which might b e resp onsible for the app earance of Balmer
line emission in early type stellar sp ectra Dr Slettebak and collab orators initially
carried out his studies from ground based data and later extended them into the
ultraviolet He has taught all of us the imp ortance of setting high standards in data
description and measurements and caution in interpretation Many of his publications
have remained b enchmarks over the years for describing sp ectral signatures of the Be
phenomenon
Dr Mercedes Jaschek was also well known for her sp ectroscopic observations of Be
stars She b egan these in Argentina and continued them when she and her husband
Carlos moved to Strasb ourg One of her ma jor contributions was the construction
of the Catalog of Stellar Groups which listed all types of stars with p eculiarities
including an extensive listing of Be stars She chaired IAU Symp osium No on
Be stars and also started the Be Star Newsletter The conference will b e op ened
by a public lecture on stars in Spanish to the lo cal lay public We plan to ask Dr
Carlos Jaschek to give this talk as an added memorial to his wife s contributions
Dr Jaschek has retired in Spain and frequently conducts informal seminars with the
public on outreach themes
The Pro ceedings
Written versions of the talks and p osters will b e published within a few months of the
conference As much space as p ossible will b e given for p oster pap ers but no limit
to p osters p er participant but the number of pages could b e limited by coverage of
discussions following ma jor talks The prop osed editors of the pro ceedings are M A
Smith talks and H F Henrichs p osters
Be Star Newsletter
PRELIMINARY AGENDA
The Be Phenomenon in Early Type Stars
Session Overview of the Be Phenomenon
De nition of the Classical Be Phenomenon
Physical Parameters and Evolutionary Status of Be Stars
Connection with Other Emission Line Stars
Session New Missions and Technologies
Positions of B Be Stars on the HRD from HIPPARCOS
Direct Optical Imaging of Be Disks
An Infrared View of Be Star Disks
A View of Isolated Be Stars at High Energies
Recent Attempts to Detect Zeeman Signal in Be Stars
Session Time Variability The Role of Stellar Atmospheric Pro cesses in Isolated
Be Stars
Subsession The Nature of Periodic Variations
Observed Periodic Phenomena
Multimo de Detections from Surveys
Comp etitive Mo dels for Periodic Variations
Subsession Rep orts on campaigns
MUSICOS
Heros
Asian Participation
IUE
Be Star Newsletter
Subsession Ap erio dic Variations
Photospheric Activity
Physical Requirements for Magnetic Flaring in an Early Type Stars
Session The Circumstellar Environment of Be Stars
Subsession Observational Diagnostics
Polarization Studies
Line Pro le Mo deling
Review of Disk Variability V R Photometric Monitoring Polarimetric Moni
toring etc
Subsession Theoretical Mo dels
Theory of Global Disk Oscillations Armed Density Wave mo del
Review of Theoretical Mo dels of Disk Formation Wind Compressed Mass
Transfer Accretion Disks etc
Session The Be Phenomenon and binary systems
Ro che lobe mass transfer systems
Wind Accretors Be X Ray Binaries
Glimpses of Binary Evolution Per etc
Session Future Directions
What Have We Concluded Synthesis of Current Understanding
Where Do We Go from Here Key Questions Problems
Be Star Newsletter
Detailed Motivation
After much electronic chat among the full SOC the enclosed preliminary program
has b een constructed The motivation for the meeting themes is as follows
Overview
The most imp ortant fo cus of the conference is to place the classical Be stars within
a larger context of early type stars with emission lines The conference will b egin
with an overview of the phenomenology of classical Be stars and recent progress in
understanding them as a class
Next we will contrast the classical Be stars with overviews of the B e and related
stars which are thought to lose or gain mass by some combination of radiation pres
sure nonradial pulsations magnetic elds and mass accretion pro cesses The relative
imp ortance of these and doubtless other mechanisms probably di ers among these
classes and in suitable parameter spaces This will b e the rst time in which par
ticipants of the classical Be massive variable sup ergiant and X ray Be stars and
are physics communities have b een assembled in order to explore the commonality
of these sub classes and to p o ol knowledge obtained among them
Results from New Missions and Technologies
Results from the HIPPARCOS mission have led to a number of imp ortant advances
in the study of Be stars including the rst reliable distances and luminosities in Be
stars and the rst meaningful p erio d luminosity diagram for pulsating B stars These
studies will lead to an improved understanding of what role evolution may play in
development of the Be phenomenon
HIPPARCOS has also b een used as a monitor of nonradial pulsations in Be stars
Its observations have b een made of a variety of ob jects at essentially random times
which will b e more e ective in the detection of multiple mo de than most previous
ground based e orts One long term study which should b e completed by the time of
this conference will have searched for the existence of many low amplitude pulsation
mo des in several Be stars from a sample which is selection free as p ossible This
research promises to supply an answer to a new degree of con dence as to whether
rare constructive sup erp ositions of these mo des can pro duce atmospheric sho cks over
short durations and eject matter from the star
Interferometric measurements have b een made already of a number of disks around
Be stars in H and in some cases in wavelengths of an optical He I line and nearby
continuum By comparing these with kinematic studies of the line pro les this work
has revealed for the rst time the size and geometry of their circumstellar disks
Moreover their apparent obliquity provides a reliable estimate of the asp ect ratio
of the disk and rotation axes Currently two research groups are continuing these
studies with a third to come on line by the time of the conference and will study
the internal velocities and degrees of inhomogeneities in disks These are critical
parameters for testing theories of disk formation We exp ect that these results could
b e announced in this conference It is anticipated that these results may b e compared
directly with new optical and UV sp ectrop olarimetry of the same Be disk systems
Results from several new X ray satellites RXTE Bepp oSax ASCA AXAF will b e
Be Star Newsletter
available at the time of the conference and will further illuminate the p ossible role of
high energy phenomena in classical Be stars as well as the connection b etween X ray
and optical variability in X ray Be binary systems This conference will also b e the
rst opp ortunity to present and discuss with the hot star community results from
ISO which b ear on the question of Be disk formation and maintenance Finally it is
anticipated that a new generation of zeeman observations will b e made of photospheric
lines in several Be stars by groups from Europ e and Canada
Temporal Phenomena in Isolated Classical Be Stars
Some p erio dic pro cess either nonradial pulsations or magnetic signals carried by ro
tational mo dulation is generally thought to b e the trigger of atmospheric instabilities
which result in spasmo dic mass ejections This conference will b e the rst o ccasion in
which monitoring of stars by HIPPARCOS over years without seasonal gaps will
b e rep orted A comprehensive rep ort on multiple p erio ds in Be stars the rst of its
kind and scop e can discuss the di erences in mo de structure and amplitude if any
b etween stars which have undergone recent Be episo des and those which have not
Some of the p erio ds discovered in these long term campaigns may b e due to rotational
passages of surface structures particularly if examination of archival repro cessed IUE
data should show variations in chemical abundances of He or Si Moreover at this
writing some of the rst rep orts are b eing published of co rotating magnetospheric
lob es over the surfaces of Be stars The study of these p erio ds will provide evidence
for the existence of quasi stable magnetic structures on these stars These studies
will address past hints of a connection b etween the Be and Bp p eculiar abundance
phenomena
A variety of studies over optical UV and X ray energies have recently shown that
rapid high energy transients o ccur often on selected Be stars These events are evi
denced as variations of UV continuum ux ephemeral features in pro les of optical
He I and H lines and X ray ares and shots Detailed studies of the pro cesses
causing these signatures and of their cascades to lower wavelengths are currently
underway and will provide exciting discussion topics for an audience comp osed b oth
of X ray and optical UV astronomers A reanalysis of repro cessed IUE data can
exploit the key He II Aline as link b etween the high energy transients and
warm star thermal background Anticipating that at least some of these signatures
could b e caused by the dissipation of magnetic energy the conference will include
a talk on the conditions needed in plasma ab ove a hot star for ares to erupt by a
prominent exp ert from the co ol star community
Circumstellar Wind and Disk Environment
In the early s the Wind Compressed Disk mo del was formulated and rst
advanced to the Be star community at the Juan les Pins symp osium This picture
was attractive b ecause it predicted the formation of disks in the out ows from sin
gle stars with mo derately high rotation rates However recent HD simulations have
shown that additional e ects can prevent the formation of the disk dep ending on
the details of the wind driving mechanism In the meantime the one armed den
sity wave mo del has b een prop osed to explain the cyclical variations of the V R
emission comp onent of Balmer lines of several Be stars A key di erence b etween
Be Star Newsletter
these pictures is whether the disks are Keplerian or angular momentum conserving
a testable prediction This conference will present b oth pictures suggest p ossible ob
servational tests investigate hybrid mo dels combining attributes of b oth and discuss
the physical forces resp onsible for their characteristics An imp ortant contribution to
the conference will b e a summary of the results of IR observations ISO SIRTF of
Be disks
Interacting Be Binary Stars
Be interacting binary systems generally are members of two groups Algol related and
Be X Ray Binaries XRBeBs Each of these represents a di erent evolutionary stage
of the mass exchange loss pro cess in these systems Somewhere b etween these stages
a Type II sup ernova can b e pro duced Several high energy studies have shown that
high temp erature accretion regions o ccur as the result of mass ow b etween these
stars Similar types of structures have b een searched for in BeXRB systems with
interestingly di erent results This meeting will b e the rst to examine the results
of searches since the last few episo des of the IUE mission when many such searches
were carried out The conference SOC will ask that typical parameter spaces of the
mass transfer energy release pro cesses b e compared for these two types of binary
systems The conference participants will b e invited to suggest observations with
new X ray satellites with enhanced sp ectral capability broad energy range and large
e ective ap erture ASCA RXTE Bepp oSax AXAF to search for the elusive but
supp osedly frequent Be white dwarf systems
Conclusions
Be stars as a group and even individually display a large variety of physical pro cesses
and therefore require a complex array of observational approaches to understand
them Within ab out two years we can hop e for a considered assessment of what
has b een learned from UV IUE data The Be community will b e intensively engaged
in research in the X ray and IR regimes The UV data have so far led to a picture
of sudden violent mass ejections from the Be star s surface A new generation of
X ray and IR missions is now p oised to provide us with new insights into the physics
of Be star disks The Alicante conference stands at a historical crossroads of these
space b orne missions the consolidation of results by one and a guide for future work
by the other The Spanish venue of this conference is appropriate as this country
has undertaken to fully exploit its Canary island observing sites and to expand its
already substantial contributions in variable star astronomy
Myron Smith SOC Chair
msmith nebula gsfc nasa gov
Be Star Newsletter
CONTRIBUTIONS
Mu Cen the ticking and ringing of a star
Th Rivinius D Baade S Ste O Stahl B Wolf and A Kaufer
Landessternwarte Heidelb erg K onigstuhl D Heidelb erg Ger
many e mail T Rivinius lsw uni heidelberg de
Europ ean Southern Observatory Karl Schwarzschild Str D
Garching b M unchen Germany e mail dbaade eso org
Astronomical Institute Academy of Sciences CZ Ond rejov Czech
Republic e mail sste sunstel asu cas cz
Received November
Introduction
In the most recent issue of the Be Star Newsletter we published a prediction of the
circumstellar activity of the Be star Cen Rivinius et al which in this regard
is one of the most proli c stars of its kind It not only exhibits low and high order line
pro le variability Baade as most other Be stars but also apparently random
and frequent line emission outbursts e g Baade et al Hanuschik et al
Peters A link b etween b oth phenomena could not so far b e established But
it now seems as if at least in Cen part of this secret could b e lifted
Photospheric lpv
Our time series analysis based on the overall radial velocities of mostly emission
free lines revealed six coherent p erio ds Rivinius et al a Rivinius et al b
Paper I Rivinius et al c Paper I I These p erio ds are sorted in two closely
spaced groups at and days resp ectively Table The trustworthiness of this
analysis is intensively discussed in Paper I I A dimensional time series analysis was
p erformed on more than sp ectral lines not only to con rm the multiperio dicity but
to derive the prop erties of either variability In each group the p erio ds are asso ciated
with identical surface variability patterns whereas these patterns di er b etween the
groups
Period P Phase at Amplitude A
days MJD km s
P
P
P
P
P
P
TABLE Parameters for the sine ts of the radial velocity variation in the line cores of
He I i e the amplitudes given are not the physical pulsation amplitudes
Be Star Newsletter
a b
c d
FIGURE The measured strength of the broad wings of the H line dots the co
added amplitudes of the day group of p erio ds line and the calculated mass ejection
lled areas The and data are the strengths of the broad emission wings
measured in H For the H equivalent width measured by Hanuschik et al
is shown Line emission outbursts start when the co added radial velocity amplitude is
maximal Note that the uncertainity of the p erio ds can cause shifts of up to ten days for
the calculation However the temp oral pattern of the outburst sequence is much more
stable against errors of the p erio ds The vertical line in panel d marks the submission date
of the prediction of the activity Rivinius et al
Constructing the ephemeris
Working on the datasets available in November we noticed that the typical
recurrence times of outbursts is on the same order of magnitude as the b eat p erio d of
the two strongest variations of the day group A rst check using only these two
p erio ds showed some alb eit weak coincidence b etween outbursts and constructive
interference of the two sinewaves by which we have approximated the measured radial
velicoity variations By taking into account all p erio ds of the day group Table
and developing an appropriate criterion for the determination of the b eginning of an
outburst in a way that is indep endent of the strength of the p ersistent disk emission
we could improve the correlation quite considerably Fig panels b and c As far
as we can see the day group of p erio ds do es not signi cantly contribute to the
Be Star Newsletter
outbursts This indicates on the one hand that interference of variabilities with dif
ferent surface patterns is much less e ective On the other hand interferences within
the day group probably do not reach the amplitude threshold which apparently
needs to b e exceeded for an outburst
In a sense we have b een extraordinarily lucky that only few combinations of variabil
ities are strong enough to trigger outbursts namely P P P P and P P the
latter b eeing already so weak that it induces only minor activity With a lower thresh
old we might have lost the p ossibility to recognize individual events Furthermore
the initially very weak emission from the disk has also help ed a lot
In an exp erimental mo del we calculated the amount of ejected mass by
allowing the amplitudes of all individual mo des to grow
de ning an outburst threshold for the vectorial amplitude sum
damping the amplitudes and ejecting mass so long as the threshold was ex
ceeded
The accuracy of the p erio ds derived allowed us to p erform an indep endent check to b e
p erformed with the data obtained by Hanuschik et al back in using the
same parameters as derived from the and data The quite successful match
b etween observations and mo del is shown in Panel a of Fig Also the outburst
event rep orted by Peters b etween April and coincides with a p ositive
amplitude interference
After reduction of our January data the mo del turned out to still work well
Fig left half of panel d But the ESO cm telescop e with which our observa
tions were mainly taken was already earmarked for mothballing after March
Accordingly further veri cation of the mo del from own observations would have b e
come di cult For this reason and encouraged by the p ositive exp erience with the
and datasets we decided to submit our prediction of the activity and a
request for help with the con rmation of the prediction already in February
although the analysis of the data was still in an intermediate working stage We
are grateful to Michelle Thaller Conny Aerts and Martin K urster for having pro
vided us with some additional sp ectra The results also of our own observations
in March and further nights with the ESO m telescop e in April are shown
on the right hand side of Panel d in Fig The coincidence of combined radial ve
locity amplitude maxima and outbursts was proven for each of the predicted events
on MJD and MJD Even the double structure of the latter event pre
dicted by the preliminary mo del with sub p eaks on MJD and MJD was
detected Unfortunately our campaign ended just b efore an exp ected second ma jor
event
In spite of the success of predicting the times of increases of the line emission from
the b eating of the radial velocity curves we will nevertheless have to revise our
preliminary and as of yet completely unphysical mo del of mass ejection Although
the structure of the bursting pattern is now repro duced in quite some detail the
calculated times of the onset of the mass ejection are for larger outburts systematically
Be Star Newsletter
to o early compared to the times when the line emission actually rises Because the
O C values do not increase with time this only shows that without a physical mo del
the outburst mechanism cannot b e prop erly understo o d
We wish to thank again Michelle Thaller Conny Aerts and Martin K urster and all
Heros observers for their observational e orts to check our prediction
We will keep the readers of the Newsletter informed by submitting the abstracts
of newly nished pap ers starting with the abstract of Paper I in this issue Our
publications are also available on the web at URL
http www lsw uni heidelberg de triviniu Bestars html
as so on as they have b een accepted refereed journal articles or submitted pro ceeding
and newsletter contributions
References
Baade D A A
Baade D Dachs J van de Weygaert R Steeman F A A
Hanuschik R W Dachs J Baudzus M Thimm G A A
Peters G J In Strassmeier K G ed Stellar surface structure IAU Symp
p oster pro ceedings Vienna p
Rivinius Th Ste S Baade D Stahl O Wolf B Kaufer A Be Star Newsletter
Rivinius Th Baade D Ste S Stahl O Wolf B Kaufer A a In Bradley P A and
Guzik J A eds A Half Century of Stellar Pulsation Interpretations ASP Conf Ser
in press
Rivinius Th Baade D Ste S Stahl O Wolf B Kaufer A b A A Paper
I
Rivinius Th Baade D Ste S Stahl O Wolf B Kaufer A c to b e submitted to
A A Paper I I
A Multi Wavelength Campaign on Gamma Cas
I I Circumstellar Structures Inferred from Ultraviolet
Continuum and Si IV Line Variations
Myron A Smith
CSC STScI
San Martin Drive
Baltimore MD
msmith nebula gsfc nasa gov
Received March
This is the third rep ort app earing in these newsletters of a optical UV X ray cam
paign carried out on the prototypical B e star Cas ab out two years ago The
thrust of the rst part of our work was to show that the X rays from this source can
b e easiest understo o d as originating from near the surface of the Be star itself with
no hypothetical companion needed Paper I Below we argue that magnetospheric
lob es exist over the star The work describ ed in the former and current rep ort have
b een submitted to the ApJ for publication and is currently in the refereeing pro cess
The authors of this Paper II are Smith R Robinson and A Hatzes If further
Be Star Newsletter
FIGURE Flux ratio curves as a function of wavelength for Cas taken during
Jan zero pts arbitrary
interested you may also consult a Web site of a press release on this sub ject at
http oposite stsci edu pubinfo pr pr html An article for Mercury maga
zine is further planned for later this year
Simultaneous X ray and UV observations over a full day on March have
b een made of Cas using the RXTE satellite and the Goddard High Resolution
Spectrograph GHRS on b oard the Hubble Space Telescope The GHRS sp ectra taken
in the region of the Si IV doublet also p ermitted the construction of
a light curve from a nearby pseudo continuum region The continuum UV and
X ray light curves from this e ort reveal a pair of X ray maxima hours apart
which coincide in time with UV continuum ux dips of In Paper I of this
series we attributed the UV dip features to magnetic activity sites on the star s
surface which undergo rotational mo dulation RM on a day p erio d In the
current study we nd that ux and color curves generated from a hour sequence
of IUE echellograms obtained in January display dip features similar to those
in the GHRS data Comparing the timings of the continuum ux dips and the Si IV
line strength variations in b oth the GHRS and IUE datasets gives a slightly revised
p erio d of days for b oth the UV and X ray activities This strengthens the
argument that high energy activity on Cas over is mo dulated by rotation of long
lived structures close to its surface
Analysis of pseudo continuum high quality mono chromatic light curve constructed
from the GHRS sp ectra and lower quality color curves constructed from the IUE
Be Star Newsletter
echellograms over a broad range of wavelengths shows at least two surprising charac
teristics for the ux dips the dips last only cycles This duration is to o brief
for rotational mo dulation of surface features and their amplitudes increase from
long to short wavelengths attaining a maximum near The IUE color curves
are shown as Figure
The character of the variations of the photospheric Si IV line pro les is also unex
p ected in that the pro le uctuations do not correlate with the slow undulations of the
continuum ux Moreover the pro le variations do not show an exp ected blue to red
migration of microfeatures Except for an interval when they showed a pair of general
weakenings and strengthenings the photospheric Si IV line pro les do not show clear
patterns During this same interval these variations showed a correlated time lag as
one samples uxes redward across the line pro le We suggest that these amorphous
variations are not caused on the surface but rather by wind inhomogeneities from
active regions on the star impacting at the inner edge of the star s circumstellar disk
We have mo deled the attenuation of ux with wavelength due to an o cculting cloud
which transits Cas with Hub eny s suite of CIRCUS SYNSPEC mo del atmosphere
program The result of these simulations is shown in Figure The solid lines
in this gure depict the ux attenuations caused by three mo dels a cloud having a
temp erature of K K or K The uncertainties in the observed amplitudes
at various wavelengths triangles decrease from ab out the size of the symbol at short
wavelengths to ab out half the size at long wavelengths
FIGURE Comparison of observed vs theoretical line blanketed color variations for
a co ol o cculting cloud
We interpret the monotonically increasing absorption toward short wavelengths as
b eing due to the strength of a strong Lyman line which can o ccur only in a co ol
Be Star Newsletter
essentially recombined gas Such co ol gas might co exist near a hot source like a
B star in the presence of thermal instabilities similar to those o ccurring in active
coronal canopies of co ol stars these are fed from the surface by a nonthermal energy
sources
o
Finally assuming a tilt of the rotational axis of to the observer s line of sight
from optical interferometry our mo del simulations of the two ma jor dips in the UV
light curves see our last rep ort indicate that the clouds have radii of a few tenths of
a stellar radius and are attached to p oints on the surface at low to mid latitudes on
the near hemisphere In all these results supp ort Paper I s conclusion that Cas is
a member of a small group of OB stars which have magnetospheres asso ciated with
X ray activity
Stellar wind variability of the Be star FY CMa
Huilai Cao and Joachim Dachs
Beijing Astronomical Observatory Beijing China
Astronomisches Institut der Ruhr Universt at D Bo chum Germany
Received January
ABSTRACT Unusual activity connected with infalling mass motions was recorded for
the B IVe star FY CMa in February b oth from archival IUE sp ectrograms of circum
stellar N v resonance lines and from optical sp ectra of H emission and He i A lines
showing inverse P Cygni type pro les We estimate the mass loss rate M to b e ab out
M yr for a spherically symmetric wind If we assume instead conical shap e for
the wind for a cone half angle of M M yr or M gm
s We attempt to give a qualitatively explanation of activity observed for FY CMa in
term of circumstellar matter raining down to the star
Introduction
Since the sp ectrum of the Be star FY CMa HR HD MWC
B IVe v sin i km s has changed quite often Merrill Burwell
noted that the hydrogen emission lines in the photographic region had disapp eared
Burbidge Burbidge rep orted that this ob ject showed double emission lines at
H and H with R V the Balmer lines from H onward app eared as absorption
only Occasional optical studies of Balmer emission lines pro les obtained for this star
at mo derate resolution A at H b etween showed FY CMa to b e in a
rather stable state of optical emission lines formation in its circumstellar disk Dachs
et al while a number of high resolution IUE sp ectrograms obtained for the
star since demonstrated strong variations of ne structure of C iv Si iv and
N v resonance absorption doublets indicating variable mass loss Grady et al
In the present work we once more want to draw attention to the fact that FY CMa
was observed in a state of unusually high activity of mass loss variations during early
as already noted by Peters and by Grady et al and that these
mass loss variation were accompanied by strong infalling motions of circumstellar
Be Star Newsletter
matter in front of the star simultaneously visible in ultraviolet N v resonance ab
sorption line pro les and in an optical He i A inverse P Cygni type line pro le
obtained by Dachs et al
Data Obtained and Reduction
Six high resolution ultraviolet sp ectra obtained b etween and
by the International Ultraviolet Explorer IUE spacecraft were provided by
the archives of the ESA Vilspa Data Center at the ESA Satellite Tracking Station at
Villafrance del Castillo Spain
Two high quality optical sp ectra of H and He i A were measured with the ESO
Coud eEchelle Sp ectrometer fed by the m Coud eAuxiliary Telescope at La Silla
Chile The instrumentation full width at half maximum FWHM measured in the
thorium lamp comparison sp ectrum corresp onds to a sp ectral resolution of mA at
either wavelength These high resolution optical sp ectrograms were supplemented
by a total of medium resolution H emission line pro les obtained for the star
b etween and by various observers of the University of Bo chum at the
cm telescop e at ESO La Silla using the University of Bo chum scanner sp ectrometer
at to A resolution as describ ed by Dachs et al Both for IUE sp ectrograms
and for optical sp ectrograms obtained at ESO reductions were p erformed bymeans
of IHAP and MIDAS image pro cessing software systems provided by ESO Radial
velocities were rst calculated in the helio centric system and then further corrected
by subtracting the radial velocity of the star listed in the Bright Star Catalogue V
rad
km s in order to obtain velocities in the stellar reference frame Typical mass
loss rates implied for FY CMa by the Si iv pro les were determined by employing
the metho d used by Snow For the ion number density fraction in the wind
N Si iv N H was adopted
Morphology of Stellar Wind Variations
Asymmetric ultraviolet resonance doublet line pro les showing stellar wind absorp
tion were insp ected on six selected IUE sp ectrograms obtained in SWP
SWP and SWP Wavelength re
gions corresp onding to N v A and to C iv absorption A are
plotted in Fig while Si iv doublet regions A are drawn in Fig As
judged from equivalent widths and asymmetries of C iv N v and Si iv absorption
pro les stellar wind in FY CMa is very strong by comparison to other Be stars of
similar sp ectral types as noted by Grady et al While no large variations
are seen in the Si iv pro les recorded b etween and Fig dramatic
variations o ccurred in the C iv and in particular in the N v pro les Fig Esp e
cially N v pro les are characterized by broad at b ottom absorption troughs in
September and November while multiple discrete absorption comp onents lo cated at
ab out and km s dominate N v pro les recorded b oth in January
and in January day By contrast one month after the January sp ec
trum had b een taken in February day N v and also C iv absorption
pro les are distinctly di erent showing evidence for simultaneous presence of out
owing and in owing motions most probably o ccurring in adjacent regions of the
visible circumstellar hemisphere in front of FY CMa While out ow is observed at
N v extending from ab out to at least km s and at C iv from ab out
Be Star Newsletter
FIGURE The sp ectral variations of FY CMa in resonance doublet lines N v and
C iv of the high resolution IUE sp ectra
km s to around km s in ow is visible b oth in C iv and N v at velocities
extending from ab out to km s
It is interesting to note that infalling motion in ab out the same velocity range was
also clearly visible in an optical He i A pro le of the star showing inverse P
Cygni type structure Fig as obtained already on February day and
describ ed earlier by Dachs et al The sequence of the optical He i A pro
le taken and the ultraviolet N v A pro le measured p oint to
an extended phase of infalling motions of highly excited plasma at electron temp er
ature T K from the circumstellar envelope of the Be star raining down to the
stellar surface and lasting at least days Grady et al In many other IUE
sp ectrograms of this star absorption by infalling matter can b e detected at similar
velocities ranging b etween and km s from transitions of ions in lower
ionization states e g from Si i i i uv A Si i i i uv A or
Fe i i i uv in A p ointing to infall of relatively co ol plasma This can b e
seen e g January or as noted by Grady et al in May Terminal
velocities of the expanding wind ows read from the pro les average around
km s for the Si iv ion and approximate km s for C iv Available medium
resolution H emission line pro les collected b etween and usually indicate
double p eak structure of the emission with violet to red p eak intensity ratios vary
ing b etween V R and Equivalent widths of H line emission recorded
range b etween W A measured on April R Hanuschik unpublished
e
and A found in November December Dachs et al
Be Star Newsletter
FIGURE Circumstellar doublet lines Si iv A had no obvious
variation during Jan Feb
FIGURE Infalling motion in the circumstellar gas surrounding FY CMa is indicated
by the inverse P Cygni pro le shown by the He i A line measured Feb
Be Star Newsletter
Discussion
The ultraviolet and optical observations clearly show that an abrupt change observed
in the circumstellar region around FY CMa involved the simultaneous presence of b oth
infall and out ow of material Peters The data which we collected showed that
this activity sustained at least days Combining our observation with Peters data
it can b e estimated that this activity p ersisted more than months Similar sudden
sp ectral variations have b een seen in pre main sequence ob jects in which accretion of
matter is o ccurring but such bursts of activity have rarely b een observed in classical
Be stars
A more plausible explanation of the abrupt activity is probably a sudden accretion
event in the circumstellar envelope as evidence for infall of matter is clearly seen in
several sp ecies of mo derate ionization Such sp ectral change could b e due to magnetic
activity i e magnetic ares or lo ops FY CMa p erhaps has large magnetic lo ops or
jets with a ow of material that originates near one of the p oles and falling down
up on the star in the line of sight In this case the line pro le presents strong blue
shift with inverse P Cygni type feature
References
Baade D Dachs J Weygaert R van de Steemann F A A
Burbidge E M Burbidge G R ApJ
Dachs J Hanuschik R Kaiser D et al A AS
Dachs J Hummel W Hanuschik R A AS
Grady C A Bjorkman K S Snow T P ApJ
Grady C A Bjorkman K S Peters G J Henrichs H F in A Decade of UV
Astronomy with IUE ESA SP Vol
Merrill P W Burwell C G Ap J
Peters G J ApJ L
Snow T P Ap J
Energy Crisis in Be star Radiation Emission
Krishna M V Apparao
Department of Physics University of Bombay
Santa Cruz East Mumbai India
Received May
This note is an attempt to draw the attention of the Be star community to the problem
of energetically accounting for the H and infrared radiation from Be stars
It is generally agreed that the emission lines observed from Be stars arise from the
gas envelope around it It is presumed that the ionization of the envelope is by
the Lyman continuum from the Be stars The ionized gas in the envelope is also
considered resp onsible for the infrared excess observed Some attempts have b een
made to quantitatively account for the H and infrared radiations from the disk
Ho ich Waters Cote and Lamers Kastner and Mazzali Kerkwijk
Waters and Marlb orough Ho ich considered a mo del in which the gas envelope
is an extension of the atmosphere of the Be star and spherical symmetry is assumed
He was able to repro duce the H equivalent widths by considering Balmer continuum
Be Star Newsletter
absorption in addition to the Lyman continuum absorption However the spherical
symmetry assumed is clearly not tenable in view of several observations Waters
Cote and Lamers Kastner and Mazzali and Kerkwijk Waters and
Marlb orough on the other hand assume a temp erature throughout the envelope
considered in order to account for the H and infrared radiation It needs to b e
shown that the assumed temp erature can o ccur throughout the envelope due to the
absorption of radiation from the Be star b efore the results can b e accepted
We have b een examining the energetics of H and infrared radiation from Be stars
by considering the absorption of all the ionizing radiation from the Be star this
should give the maximum p ossible ionization by the radiation Apparao and Tarafdar
a b We have assumed the Lyman and Balmer continua given by
atmospheric calculations of Kurucz for various sp ectral types of Be stars and
considered their absorption for ionizing the Be star envelope In the rst publication
we have calculated the energy in the H emission due to the absorption of Lyman
and Balmer continua from the Be stars and compared the results with observations
We found that the observations can b e accounted for Be star sp ectral types up to B
see Table the emission from later sp ectral types cannot b e accounted for by the
ab ove pro cess We had suggested the need for additional ionizing photons
TABLE H Emission HI I Region formed by Be and He stars
Sp ectral Temperature Lyman Balmer Observed
Type K erg s erg s erg s
B E E E
B E E E
B E E E
B E E E
He E E
He E E
The values given are the maximum observed values
In Apparao and Tarafdar a we suggested that in the case of late type Be stars
a He star binary companion to the Be star can supply the necessary ionizing photons
see Table We had shown that the He star will not visible in the glare of the
Be star optical emission This will imply that all the late type Be stars which are
observed to emit H emission have a He star binary companion and for those without
a He star companion though having a gas envelope H emission will not b e detected
Some of the other consequences of our suggestion are given in the pap er
We have examined whether the observed infrared excess for Be stars these consider
ations do not p ertain to B e stars where the infrared emission is b elieved to o ccur
from heated dust can b e accounted for by free free emission by the gas envelope
ionized by the Lyman continuum of the Be star Apparao and Tarafdar b The
calculated values and the observed values are given in Table
Be Star Newsletter
TABLE Infrared Emission HI I Region around Be Stars
a
Sp ectral IR from Calculation IR from Observation
Type ergs s ergs s
b
E E
B E E
B E E
B E E
B E E
a
Highest values observed for the sp ectral type Ashok et al
b
Observed value for X Per when not p eak emission Ro che et al
It is seen from Table that the infrared emission calculated from the absorption of the
Lyman continuum is inadequate to account for the observed infrared emission from
Be stars of sp ectral types of B and later In the case of sp ectral types greater than
B the energy in the Lyman continuum itself is smaller than that in the observed
infrared radiation
How then the infrared emission is energized We had considered two p ossibilities
Be stars emit a Lyman continuum more copiously than given by the atmospheric
calculations of Kurucz or additional ionizing photons are supplied by a
companion star to the Be star He star white dwarf or neutron star
Observations of the star Epsilon CMa Cassinelli et al by the EUVE Satellite
has shown that the EUV ux is ab out thirty times the ux given by atmospheric
calculations Mo di cations of the atmospheric calculations could not explain the ob
servations so far and the origin of this ux remains obscure However the p ossibility
exists that B and Be stars emit EUV ux more copiously than given by the atmo
spheric calculations If this is true then the observed infrared and H uxes for
Be stars at least for the early sp ectral types can b e accounted for energetically
However the problem still remains for the late sp ectral types
The required ionizing photons to account for the infrared and H uxes from Be
stars can easily b e supplied by the presence of a compact ob ject He star white
dwarf or neutron star in binary motion around the Be star The formation of such
binaries was discussed by Pols et al The surface temp erature of the He star
is high enough to supply the requisite photons Apparao and Tarafdar a If the
compact ob ject is a white dwarf or neutron star matter accretion is needed to give
out ionizing photons The presence of a neutron star is indicated by an X ray ux
but the presence of a white dwarf star is di cult to detect due to absorption of the
radiation by the Be star envelope itself Apparao The detection of white dwarf
and He stars in the far and extreme UV is discussed in Apparao and Tarafdar a
b As mentioned earlier the presence of a He star will b e di cult to detect in
the visible region due to the brightness of the Be star
There is enough energy in the Balmer continuum of Be stars to account for the
observed infrared and H emissions However a pro cess by which the energy can b e
utilized to provide the necessary ionization has not b een found yet
The suggestion that the ionizing photons to account for the infrared and H emissions
come from a compact ob ject implies that all the Be stars at least the later sp ectral
Be Star Newsletter
types are binaries Even though this is a p ossibility considered earlier by other
authors e g Harmanec there is no evidence to supp ort this contention
We suggest that at present the accounting for the energy needed for infrared and H
emissions of Be stars is not done adequately Further observations and theoretical
work are needed to give an answer
Acknowledgments I thank the Indian National Science Academy for a Senior Scientist
Fellowship I thank the Director of Tata Institute of Fundamental Research for use
of the library and other facilities I thank Prof S B Patel and other colleagues at
the Bombay University
References
Apparao K M V and Tarafdar S P ApJ
Apparao K M V and Tarafdar S P a Bull Astr So c Ind
Apparao K M V and Tarafdar S P b J Astrophys Astr
Ashok N M et al MNRAS
Cassinelli J P et al ApJ
Harmanec P IAU Collo quium no
Ho ich P A A
Kastner J H and Mazzali P A A A
Kurucz R L ApJS
Pols O R Cote J Waters L B F M and Heise J A A
van Kerkwijk M H Waters L B F M and Marlb orough J M A A
Waters L B F M Cote J and Lamers H G J L M A A
Be Star Newsletter
WHAT S HAPPENING
Discovery of p erio dic brightenings in the B variable
HD
Petr Harmanec
Astronomical Institute Academy of Sciences of the Czech Republic
Ond rejov Czech Republic e mail hec sunstel asu cas cz
Received July
Hrvo je Bozic and I have published in A A A A a short pap er in
which we rep ort our discovery of a little studied B variable HD for which we
found o ccasional and p ossibly regular brightenings for ab out mag in V We
susp ect that the brightenings could re app ear with a p erio d of d and I decided
to alert readers after I realized that if we are right the next brightening should
o ccur literary these days centred on August You can get a p ostscript copy
of our pap er from anonymous ftp to sunstel asu cas cz directory
pub hd
A Painting of the Be sdO Binary Phi Persei
Douglas R Gies
Center for High Angular Resolution Astronomy and Department of Physics
and Astronomy
Georgia State University Atlanta GA e mail gies chara gsu edu
Received February
A recent issue of ApJ Gies et al ApJ contains our rep ort on new
UV sp ectroscopy made with the Hubble Space Telescope and Go ddard High Resolu
tion Sp ectrograph of the unusual binary system Phi Persei This system contains
a rapidly rotating Be star orbiting a hitherto unseen companion in a day orbit
The new HST GHRS sp ectra show for the rst time clear evidence of the compan
ion s sp ectrum it is a hot K small star M which is presumably the
stripp ed down remains of a much more massive star which lost b oth mass and angu
lar momentum to the companion which is spinning at close to the critical break up
sp eed The new results are imp ortant for several reasons
This is the rst time we have actually observed this stage in massive star binary
evolution
The observations demonstrate that rapidly spinning Be stars can b e formed
through binary pro cesses
The companion a hot sub dwarf represents the brightest such ob ject in the sky
but hitherto lost in the glare of the Be star
Be Star Newsletter
The Outreach O ce of the Space Telescope Science Institute was interested in mak
ing a WWW News Release ab out this work but we needed some kind of image to
accompany the text I contacted Bill Pounds an astronomical artist living here in
the Atlanta and with the help of Jon Bjorkman University of Toledo and others
Bill pro duced a b eautiful and hop efully accurate rendering of what Phi Persei might
lo ok like close up The painting and press release are available on the WWW at URL
http oposite stsci edu pubinfo pr html and the painting graces the
cover of this issue of the Be Star Newsletter
The painting depicts the binary system for an assumed inclination of and an
orbital phase just prior to primary sup erior conjunction The Be primary upper
right app ears oblate and gravity darkened b ecause of its extremely fast rotation
V sin i km s The surrounding circumstellar disk was made assuming a
Gaussian intensity distribution based on interferometric measurements Quirrenbach
et al ApJ and the Hipparcos distance estimate p c and the red
colour re ects the dominance of the H ux The inner edge of the disk facing the
companion has a brighter app earance b ecause we b elieve it is heated there by the
secondary observed in the app earance of Fe IV shell lines in the HST sp ectra at this
orbital phase The hot sub dwarf secondary app ears in the foreground lower left
with radial features suggesting its strong stellar wind see Thaller et al ApJ
The secondary also has a circumstellar disk seen in the He II line
which we imagine results from infall from the Be star s disk
Hop efully future interferometric observations will show how closely this painting
matches the real situation
Interferometric Results Highlighted on WWW Site
Philipp e Stee
Observatoire de la Cote d Azur Departement Fresnel UMR Equip e
GI T route de l Observatoire Caussols St Vallier de
Thiey France e mail stee obs nice fr
Received January
I have assembled on my World Wide Web site a number of pap ers and results re
lated to high resolution studies of hot stars Interested readers can nd the page at
http www obs nice fr stee bienvenue html
Be Star Newsletter
Atlas of Sp ectrop olarimetric Observations of Be Stars
Karen Bjorkman
Ritter Observatory Department of Physics and Astronomy University of
Toledo Toledo OH e mail karen astro utoledo edu
Received January
We are in the pro cess of putting together an atlas of sp ectrop olarimetric observations
of Be stars using data taken at the University of Wisconsin s Pine Blu Observatory
from a second installment later will include data from onward Part
of this publication will include a web based atlas to allow easy access to the data
by the astronomical community Sample pages from the atlas were presented at the
January AAS meeting in Washington DC
In order to make this atlas as useful as p ossible we are soliciting feedback from
p otential users ab out the tentative layout of the web pages If you would b e interested
in having a lo ok at our sample pages please p oint your Web browser to the following
URL http www sal wisc edu HPOL atlases bes
Any feedback or suggestions you would care to o er would b e greatly appreciated
You can send your comments via e mail to either me karen astro utoledo edu or to
Marilyn Meade meade sal wisc edu
Thanks for your assistance
Be Star Newsletter
ABSTRACTS
Photometric Monitoring of Bright Be Stars I I I
and
John R Percy Jason Harlow Katharine A S Hayhoe Inese I Ivans
Matthew Lister Rene Plume Tara Roseb ery Sarah Thompson
and David Yeung
Erindale College and Department of Astronomy University of Toronto Mississauga Ontario Canada
L L C
We rep ort long term photometric BV observations of bright active Be stars
made in and and to with the m telescop e at the University of
Toronto Cumulative light curves including observations made earlier at the Univer
sity of Toronto and with the Automatic Photometric Telescope Service in Arizona
are presented for several of the stars Many of the stars show cyclic variations of up
to in V and B on time scales of a few years as well as variations on time scales
of ab out a day
PASP
On the sp ectacular variations of Cas Evidence
for a temp orarily tilted circumstellar disk
W Hummel
Universit atssternwarte M unchen Scheinerstr D M unchen Germany
A new explanation for the sp ectacular emission line variations o ccuring in the Be
stars Cas and Cyg is presented We prop ose a circumstellar Keplerian disk
tilted with resp ect to the equatorial plane The precessing no dal and apsidal line
causes a variation in the emission line widths and pro le shap es In particular the
sequence of alternating shell phases and narrow single p eak phases is prop osed to b e
due to an apparent variation in the disk inclination
A A
Long term visual sp ectrophotometric b ehaviour
of Be stars
A Moujtahid J Zorec A M Hub ert A Garcia and D G Burki
1
Observatoire de Paris Meudon DASGAL F Meudon Principal Cedex France
2 bis
Institut d Astrophysique de Paris C N R S b d Arago F Paris France
3
Observatoire de Gen eve CH Sauverny Switzerland
The long term sp ectrophotometric variations of Be stars are studied using the U
and V magnitudes of the UBV system the total Balmer discontinuity D and the
Be Star Newsletter
visible gradient BCD sp ectrophotometric and photometric data in ve di erent
rb
photometric systems obtained in most cases since and reduced to the BCD
system were used The U D V D D and V correlations obtained
rb rb
di er from star to star and they can b e single or double valued They di er clearly
for Be phases or Be shell phases Be stars with small V sin i showing the sp ectropho
tometric shell b ehaviour D D were found This nding implies either that
strongly attened mo dels of circumstellar envelopes are in doubt for these stars or
that not all Be stars are rapid rotators Comparison of observed variations with those
predicted for mo del Be stars with spherical circumstellar envelopes of variable den
sities and dimensions implies that sp ectrophotometric patterns of Be phases are due
to circumstellar envelopes in low opacity regimes while those of sp ectrophotometric
shell phases are due to circumstellar envelopes in high opacity regimes In a given
star the envelope regions resp onsible for the observed variations of D and in
rb
sp ectrophotometric shell phases seem to b e smaller and denser than those pro ducing
the observed variations of these parameters in sp ectrophotometric Be phases The
high p ositive RV found in strong shell phases might favor the formation of compact
circumstellar layers near the star
A AS
The optical counterparts to Be X ray binaries in
the Magellanic Clouds
J B Stevens M J Co e and D A H Buckley
1
Dept of Physics and Astronomy University of Southampton High eld
2
South African Astronomical Observatory P O Box Observatory South Africa
The elds of X ray sources in the Magellanic Clouds b elieved to b e Be X ray binaries
have b een searched for p ossible Be star counterparts BVR and H CCD imaging was
employed to identify early type emission stars through colour indices and H uxes
Follow up H sp ectroscopy of sources con rms the presence of H emission in each
case Based on the p ositional coincidence of emission line ob jects with the X ray
sources we identify Be star counterparts to the ROSAT sources RX J RX
J RX J and RX J and to the recently discovered
ASCA source AX J We con rm the Be star nature of the counterparts to
the EXOSAT source EXO and the HEAO source H In the
eld of the ROSAT source RX J we nd three p ossible counterparts each
showing evidence for H emission
Submitted to MNRAS
Preprints from jbs astro soton ac uk
HIGH STATE OF H EMISSION ACTIVITY
OF THE HERBIG Be STAR HD
Anatoly S Miroshnichenko Christopher L Mulliss Karen S Bjorkman
Be Star Newsletter
Nancy D Morrison Yuri V Glagolevskij Georgij A Chountonov
1
Ritter Observatory Dept of Physics Astronomy The University of Toledo Toledo OH
USA
2
Sp ecial Astrophysical Observatory of the Russian Academy of Sciences Karachai Cherkess Re
public Nizhnyi Arkhyz Russia
We present the results of high resolution sp ectroscopic observations of the pre main
sequence Herbig Be star HD obtained b etween September and February
Strong variations of the H line asso ciated with an extended p erio d of strong
emission during summer and fall have b een observed The line equivalent width
to ok on the highest value rep orted in the last years Evidence of a strong stellar
wind followed by enhanced accretion of circumstellar matter onto the star as sug
gested previously by Beskrovnaya et al A A is con rmed A
review of the observational literature dating back to indicates p erio dic b ehav
ior of the H equivalent width with a p erio d of years The next high emission
state is predicted to o ccur in the rst half of We emphasize the imp ortance of
co ordinated photometric and high resolution sp ectroscopic observations for further
understanding of the star s b ehavior
Submitted to PASPFor preprints contact anatoly physics utoledo edu
or by anonymous ftp to ftp physics utoledo edu users anatoly hd
Evidence for one armed oscillations in the
equatorial disk of Tau from GI T sp ectrally
resolved interferometry
F Vakili D Mourard Ph Stee D Bonneau P Berio
O Chesneau N Thureau F Morand A Lab eyrie and I Tallon Bosc
1
GI T Fresnel Observatoire de la C oted Azur F Caussols France
2
Observatoire de Haute Provence Saint Michel l Observatoire France
3
Centre de Recherche Astronomique de Lyon UMR CNRS avenue Charles Andr e
St Genis Laval Cedex France
We rep ort sub mas observations of the Be Shell star Tau with the Grand In
terf erom etre a T elescopes GI T on November and Octob er In the
H line presented a V R ratio of with a central absorption shell comp onent
On Octob er the H line presented a reversed V R ratio of with a shallower
absorption comp onent For b oth ep o chs we analysed the amplitude and phase of the
fringe signal relative to the lo cal continuum as a function of Doppler shift across H
We clearly resolve the H emitting envelope on Octob er We nd that the bulge
of the emission which o ccurs around RV km s has a N S pro jected p osition
of mas to the South of the continuum source This value corresp onds to a linear
separation of photospheric radii For Octob er the same analysis shows that
the pro jected p osition of this bulge o ccuring around RV km s has moved to
mas i e photospheric radii North of the continuum source On account of
the opp osite V R values b etween and and the long term H cyclic variability
of Tau this apparent motion corresp onds to the rst interferometric detection of an
Be Star Newsletter
axi asymmetric envelope around a Be star that we interpret as direct evidence for a
prograde one armed oscillation of its equatorial disk
Accepted by Astronomy Astrophysics Main Journal March
Preprints from vakili obs azur fr
Stellar and circumstellar activity of the Be star
Cen I Line emission outbursts
Th Rivinius D Baade S Ste O Stahl B Wolf and A Kaufer
1
Landessternwarte K onigstuhl Heidelb erg Germany
2
Europ ean Southern Observatory Garching b ei M unchen Germany
3
Astronomical Institute Academy of Sciences Ond rejov Czech Republic
With a total of echelle sp ectra obtained with Heros Heidelb erg Extended Range
Optical Sp ectrograph during observing runs covering nights in years and the
sp ectral range from to A at a resolving p ower of this study is
based on one of the most extensive homogeneous observational records of the short
medium and long term variability of any Be star One week worth of low resolution
sp ectra with very high temp oral sampling was additionally obtained Three dense
series of very high resolution low noise pro les of He i observed in
sp ectra and one of Si i i i obtained in sp ectra simultaneously to
the low resolution data could also b e relied up on for veri cation purp oses
The star was found to b e in the pro cess of continued gradual recovery of the H
emitting disk which had b een lost from During the monitoring p erio d
numerous line emission outbursts were observed A detailed generalized pattern of
an outburst cycle is derived from observations of di erent circumstellar lines at times
of various levels of emission from the disk Relative quiescence precursor outburst
and subsequent relaxation can b e distinguished as the main constituing phases even
though there are distinct di erences b etween di erent groups of sp ectral lines
Outbursts are preceded by a signi cant decline in the p eak height of all circumstellar
emission lines which only lasts a few days The outbursts prop er are characterized
by the o ccurrence within days of i broad emission wings ii rapid cyclic vari
ability of the violet to red V R emission p eak ratio iii temp orary high velocity
absorptions iv transient sharp absorption spikes at the edges of photospheric lines
v an increase in the separation of emission p eaks and vi an increase of emission
strength as the burst go es on Particularly the V R activity may b e accompanied by
relatively short lived narrow blueshifted high velocity absorption comp onents The
relaxation phase following the outburst exhibits a slow but steady decline from these
sudden enhancements and ultimately returns to the pre outburst state of relative qui
escence Outbursts can di er in amplitude and duration by a factor of a few and
the larger an outburst is the more time it takes relative quiescence to b e reached
At times the frequency of outbursts is so high or the amplitude of an outburst is so
large that the next outburst takes place b efore the previous pre outburst state has
b een re established
Be Star Newsletter
Based on this empirical phenomenology a schematic picture of the asso ciated ejection
of matter into a near stellar orbit is sketched
A A
Stellar and circumstellar activity of the Be star
Cen I I Multip erio dic low order line pro le
variability
Th Rivinius D Baade S Ste O Stahl B Wolf and A Kaufer
1
Landessternwarte Heidelb erg K onigstuhl D Heidelb erg Germany
email T Rivinius lsw uni heidelb erg de
2
Europ ean Southern Observatory Karl Schwarzschild Str D Garching b M unchen
Germany e mail dbaade eso org
3
Astronomical Institute Academy of Sciences CZ Ond rejov Czech Republic
e mail sste sunstel asu cas cz
After the study in Paper I of the morphology of the line emission outbursts of this
bright Be star the same database is analyzed for the temp oral characteristics of the
photospheric variability
In the sp ectra separate time series analyses were p erformed for the mean
radial velocities of two groups of lines He I and Si I I I which were selected for their
b eing the least contaminated by emission comp onents A p erio d search with iterative
pre whitening revealed six p erio ds which maintained phase coherence over the entire
time interval covered Four of them are close to the previously rep orted day
p erio d and in fact constitute it Their relative frequency spacings are ab out
and again and cannot b e resolved in single season data strings The other
two p erio ds which were not found in the Sii i i lines are near day Additionally
the radial velocity variations of the single line He I were studied This data
set extends from to thereby p ermitting a re nement of the p erio ds found
in the other lines
Similar time series analyses of the ux contained in km s wide line pro le bins of
the sp ectra found p erio ds that are identical to those of the radial velocities
to within decimal places However not all p erio ds are detected in all lines
studied
Within either group of p erio ds the line pro le variability patterns are indistinguish
able from one another whereas the di erence b etween the two groups is highly signi
cant This implies that there are also two di erent stellar surface patterns asso ciated
with the two groups Their analysis is deferred to the third pap er in this series
Numerous di erent tests were p erformed to check the genuineness of the multiperi
o dicity None of them could disprove the reality of any of the p erio ds which seems to
b e well founded on many observational facts
At times of enhanced V R variability an additional line pro le mo dulation with
p erio d day may develop It consists of narrow absorption spikes at
Be Star Newsletter
v sin i and in the resp ective opp osite wing a very extended ramp like ascent of
the pro le to the adjacent continuum
Finally a series of low resolution sp ectra obtained during nights which coin
cided with a line emission outburst indicates cyclic variations of the radial velocity
of Balmer and He I lines with a time scale of day The same time scale was also
present in the V R ratio of the two emission p eaks in H
Submitted to Astronomy Astrophysics
Preprints wil l be available from the rst author after the paper has been accepted for
publication
Multip erio dic line pro le variability and a
tentative ephemeris for line emission outbursts of
the Be star Cen
Th Rivinius D Baade S Ste O Stahl B Wolf and A Kaufer
1
Landessternwarte K onigstuhl Heidelb erg Germany
2
Europ ean Southern Observatory Garching b ei M unchen Germany
3
Astronomical Institute Academy of Sciences Ond rejov Czech Republic
Between and the bright Be star Cen was monitored sp ectroscopically
with a high resolution echelle sp ectrograph A thorough p erio d analysis of the stellar
radial velocity could resolve the previously susp ected day p erio d into distinct
closely spaced p erio ds The line pro le variations asso ciated with all three p erio ds
are ab out the same and can b e b est describ ed as a roughly sinusoidal low order
mo dulation of the line pro les A fourth mo de with higher frequency in b oth the
spatial and temp oral domain was also detected Qualitatively low order NRP g
mo des of di erent high radial degree can readily serve as a p ossible interpretation
This might op en meaningful asteroseismological opp ortunities
From the phases and mean amplitudes of the three day p erio ds the times of
maximal amplitude sup erp osition were re constructed which correlate well with the
times of the observed increases of the emission line strength This may lead to a
revival of the notion of pulsationally driven outbursts of Be stars
To app ear in A Half Century of Stellar Pulsation Interpretations A
Tribute to Arthur N Cox held in Los Alamos in June eds P A
Bradley and J A Guzik
Preprints from T Rivinius lsw uni heidelberg de
or on the web at http www lsw uni heidelberg de triviniu Bestars html
Circumstellar quasi p erio ds accompanying stellar
p erio ds of Be stars
S Ste D Baade Th Rivinius O Stahl B Wolf and A Kaufer
1
Astronomical Institute Academy of Sciences Ond rejov Czech Republic
2
Europ ean Southern Observatory Garching b ei M unchen Germany
Be Star Newsletter
3
Landessternwarte K onigstuhl Heidelb erg Germany
Several hundred high sp ectral and temp oral resolution sp ectra nm of three
southern Be stars obtained in three seasons were used for time series analyses of line
pro les The p erio dicity pattern di ers signi cantly i across a given line pro le
i i b etween di erent sp ectral lines and i i i b etween di erent phases of an emission
outburst cycle In some seasons newly discovered transient p erio ds co exist with
the main stellar p erio ds which maintain long term stability and phase coherence
They di er typically by from the main p erio ds less from transient p erio ds at
other ep o chs and are not present in purely photospheric lines but can b e dominant
in the lines formed in the upp er parts of the extended atmosphere The nature of
the phenomenon and concerns ab out implications for studies of rapid variability are
discussed
To app ear in A Half Century of Stellar Pulsation Interpretations A
Tribute to Arthur N Cox held in Los Alamos in June eds P A
Bradley and J A Guzik
Preprints from sstefl sunstel asu cas cz
or on the web at http www lsw uni heidelberg de triviniu Bestars html
Weak and Post T Tauri Stars around B type
members of the Sco Cen OB asso ciation
E L Martin
1
Astronomy Department University of California Berkeley CA
2
Instituto de Astrof sicade Canarias La Laguna Tenerife Spain
I rep ort medium resolution FWHM A sp ectroscopic observations of six H
emission stars prop osed by Meyer et al to b e T Tauri stars formed in the
vicinity of the B giant Sco a bright member of the Sco Cen OB asso ciation Us
ing sp ectroscopic criteria sp ectral types H and LiI equivalent widths which are
distance indep endent I classify these stars in di erent PMS classes Taking data
from the literature a number of stars detected by X ray observations around other
B type members of Sco Cen are also classi ed The current census of b ona de
low mass PMS stars identi ed in ab out deg in Sco Cen is CTTS WTTS
and PTTS The presence of a mixture of T Tauri and p ost T Tauri stars implies
that previous results based on iso chrone tting that indicated an extremely young
age Myr for the Sco Cen PMS low mass p opulation are incorrect A distance of
ab out p c for Sco Cen instead of the p c used in previous works is consistent
with the Hipparcos parallaxes for many of the B type stars and would lead to older
H R diagram ages Taking into account that PTTS are generally fainter and harder
to identify than WTTS I argue that the WTTS PTTS ratio in Sco Cen may b e of
order of unity This result suggests that the low mass stars of the OB asso ciation span
an age range similar to the B type members Myrs i e the low and high mass
star p opulations are essentially co eval Sco Cen app ears to b e indeed a promising
place to nd many PTTSs in future surveys
Be Star Newsletter
Coupled long term photometric and V R
variations in Be stars evidence for prograde
global one armed disk oscillations
R E Mennickent C Sterken and N Vogt
1
Dpto de F sica Facultad de Ciencias F sicasy Matem aticas Universidad de Concep ci on Casilla
Concep ci on Chile
2
University of Brussels VUB Pleinlaan Brussels Belgium
3
Departamento de Astronom ay Astrof sica Ponti cia Universidad Cat olicade Chile Casilla
Santiago Chile and Sternwarte Sonneb erg Sternwartenstr D Sonneb erg Germany
We review theoretical work on global oscillations of Be star disks and summarize
p ossible observational tests In addition we analyze existing records on photometric
data and V R ratio for a sample of V R variable Be stars Five stars showed
coupled long term photometric V R variations In all cases the photometric extrema
coincided with times of V R transits the fainter state b eing followed by a V R
phase V Aql Lib and MX Pup showed anticorrelated c and b y colors during
light cycles the stars b eing redder in b y when brightest Lib shows a complex
color b ehaviour exhibiting two minima during a V R cycle and a pronounced b y
drop just at maximum light In addition this star shows enigmatic non p erio dic
eclipse like features in its light curve In general the V R photometric observations
can b e group ed in three main groups dep ending on the degree of correlation exhibited
by the V R ratio and the photometric uxes and the rate of change of the u ux
These groups are compatible with prograde global disk oscillations observed under
di erent system inclinations
A A
Long Term Photometry of Be stars I I I Evidence
for p erio dic outbursts of Eri and photometric
activity in HR
R E Mennickent C Sterken N Vogt
1
Dpto de F sica Facultad de Ciencias F sicasy Matem aticas Universidad de Concep ci on Casilla
Concep ci on Chile
2
University of Brussels VUB Pleinlaan Brussels Belgium
3
Grup o de Astrof sica Universidad Cat olicade Chile Casilla Santiago Chi le
4
Sternwarte Sonneb erg Sternwartenstr D Sonneb erg Germany
Str omgren di erential uv by photometry of Eri and HR is analyzed The
data were taken during the time interval in the framework of the Long
Term Photometry of Variables pro ject at La Silla Eri exhibited four photometric
events probably asso ciated with line emission episo des that last several months and
which were characterized by a common pattern of change in all passbands
Be Star Newsletter
mag day along with an apparent decrease of the amplitude of the short term vari
ability and an increase of the stellar temp erature A search for p erio dicities reveals
that these events t a d recurrence time On the other hand HR showed a
relatively quiet long term photometric b ehaviour the orbital p erio d b eing detected
only marginally in the photometric data set In contrast a d p erio d optimally
ts the data We discuss the p ossibility of an internal clo ck regulating the outburst
activity of Eri and show that the photometric variability of HR can hardly b e
explained by its interacting binary nature We also discuss an empirical relationship
c
1
and v sini in a sample of Be stars found b etween
u
A A
On the inner envelope of the Be star Gamma Cas
Ph Stee F Vakili D Bonneau and D Mourard
GI T Fresnel Observatoire de la C oted Azur F Caussols France
We rep ort the rst sp ectrally resolved observations of the Be star Cas in the He
I and H emission lines using the Grand Interf erom etre a T elescopes in
the southern France Milliarcsecond angular resolution measurements were carried
in b oth lines and their neighbouring continuum during Octob er and November
The He I and H maximum emissions corresp ond resp ectively to and
of the lo cal continuum level The interferometric baselines ranged from m to
m on the sky which corresp ond to angular resolutions of to mas at HeI
and to mas at H wavelengths We compare these values to predicted extents
of H and He I comp onents of the circumstellar gas from mo dels of radiative
transfer in these lines We conclude that the emitting region must b e smaller than
stellar radius in H and close to stellar radius in He I which is for He I
smaller than the nearby continuum extent These results con rm Cas basic
parameters for this star obtained by Stee et al in from their mo del constrained
by GI T observations in the H line
A A
The Equatorial Disc of the Be Star X Persei
J H Telting L B F M Waters P Ro che A C A Bo ogert
J S Clark D de Martino and P Persi
1
Astronomical Institute Anton Pannekoek University of Amsterdam and Center for High Energy
Astrophysics Kruislaan SJ Amsterdam Netherlands
2
Isaac Newton Group of Telescopes ASTRON NFRA Apartado Santa Cruz de La
Palma Spain
3
Astronomy Centre CPES University of Sussex Falmer Brighton BN QH UK
4
Kapteyn Institute p o b ox NL AV Groningen Netherlands
5
Physics Department University of Southampton Southampton SO BJ UK
6
ESA IUE Observatory VILSPA Villafranca Apartado
Be Star Newsletter
Madrid Spain
7
Osservatorio Astronomico di Cap o dimonte via Moiariello
I Nap oli Italy
8
Instituto di Astro sica Spaziale CNR C P I Frascati Italy
We have studied the long term b ehaviour of the equatorial disc of the Be X ray binary
X Persei combining new low resolution IUE sp ectra and IR photometry with UV
optical and IR observations collected from the literature
We nd that the near UV continuum level of X Per varies along with the optical
brightness From the UV observations we nd that during optical high states the ux
excess due to the intrinsic stellar variability and or electron scattering in the disc is
at most of the photospheric ux
From the data taken in discless and near discless states optical low states we derive
that the stellar photosphere can b e mo delled with T K and log g With
e
this mo del we derive E B V and estimate the distance to X Per as
parsec assuming R R
We t the quasi simultaneous optical and IR photometry with a simple disc mo del
including free b ound and free free radiation We nd that the density of the disc
at the photosphere of the star varies along with the brightness of X Per and that
in optical high states the disc in X Per is among the densest of all Be stars
gcm The disc density at the photosphere varies by a factor of at
least from optical high to low states
During disc build up and break down phases and also in phases when the disc is
relatively stable we nd a very steep radial density gradient of the disc of X Per
This may re ect the limitations of some of the assumptions in our mo del
We nd that in a disc loss event the disc loses mass at a rate of ab out M year
For a disc build up phase we nd a disc mass growth rate of ab out M year
This growth rate is consistent with a mo del that feeds the disc from the ordinary
mass loss of the star but we cannot exclude that other phenomena contribute to the
disc growth as well
MNRAS
The Development and Behavior of an Active
Region On Near the Photosphere of the B e Star
Centauri
Geraldine J Peters
Space Sciences Center University of Southern California University Park Los Anglees CA
USA
An unusual mass loss event observed in the B e star Cen during the course of
days in April is describ ed and discussed within the framework of contemporary
Be Star Newsletter
d
ideas on the Be phenomenon The onset of the activity o ccurred in less than
and was characterized by variable emission in He I that displayed a distinctive
character Unlike the transient micro emission in He I that frequently o ccurs in Cen
and other Be stars the emission line variations seen in this event to ok place more
slowly in three discrete velocity intervals On two o ccasions violet v and red r
shifted emission comp onents declined on a time scale of hr while the emission
at near the line center increased The short time scale and observed velocity b ehavior
suggest the site of the activity was near the photosphere The p ossible imp ortance
of nonradial pulsations and magnetic elds in precipitating the event is discussed A
scenario is suggested to explain the observations in which material originating from
an active site on the photosphere is injected into a slab Layers in the active region
b ecome visible in He I as the prevailing density builds to values favorable for
the pro duction of this emission line It is estimated that the slab covered of the
star A increase in the H emission strength by the nal day of the observations
indicates that the activity did indeed add material to the circumstellar disk
Accepted by Astrophysical Journal Letters
Preprints from gjpeters mucen usc edu
B e stars IV HD MWC
Yvette Andrillat Carlos Jaschek and Mercedes Jaschek
1
Lab oratoire d Astronomie Universit ede Montpellier URA et CNRS Place Eugne
Bataillon F Montpellier France
2
Observatoire de Strasb ourg URA CNRS rue de l Universit e F Strasb ourg France
3
deceased
On the basis of sp ectroscopic CCD material obtained at the Haute Provence Ob
servatory we provide line identi cations and equivalent width measurements in the
wavelength regions and A of the sp ectrum of HD Over
features are identi ed and a comparison of our results with those of other authors
is provided We also discuss the variability of the lines using equivalent widths and
the line sp ectrum We conclude that the gaseous shell surrounding the star has a
temp erature of the order of K and that its distance to the star is less than ten
stellar radii We discuss the similarity of this star to other stars previously analyzed
A AS
B e stars V HD MWC
Carlos Jaschek Yvette Andrillat
1
Observatoire de Strasb ourg URA CNRS rue de l Universit e F Strasb ourg France
2
Lab oratoire d Astronomie Universit e de Montpellier URA et CNRS Place
Eugne Bataillon F Montpellier France
On the basis of sp ectroscopic CCD material obtained at the Haute Provence Ob
servatory we provide line identi cations and equivalent width measurements in the
Be Star Newsletter
wavelength region Aof the sp ectrum of HD Over two hundred
features are identi ed and a comparison of our results with those of other authors
is provided We also discuss the variability of the lines using equivalent widths and
descriptions of the line sp ectrum We attribute as a b est compromise a sp ectral type
of B I I I We conclude that the gaseous shell surrounding the star has a temp erature
of the order of K and that its distance to the star is of the order of two stellar
radii We discuss the relation of this star to others previously analyzed and warn
against hasty generalizations
A AS
Be Star Newsletter
On the nature of the Be phenomenon The case
of Omega CMa
P Harmanec
Astronomical Institute Academy of Sciences CZ Ondrejov Czech Republic
Internet hec sunstel asu cas cz hec mbox cesnet czls
The main purp ose of this pap er is to demonstrate the extreme complexity of the
observed variations of Be stars on the example of a well observed bright Be star
CMa A detailed analysis of all published radial velocities and a representative
set of photometric and sp ectral observations of this star led to the following rm
conclusions
At least three and p ossibly four di erent time scales of variability of CMa
ranging from d to more than years could b e identi ed
The correct mean p erio d of the RV and line pro le changes is d not
d as derived earlier
The brightness of the ob ject and the strength of the Balmer emission vary in
an apparent cycle of several thousands of days The long term brightness and
emission line changes can b e understo o d as consequences of the formation and
gradual disp ersal of a gaseous envelope which is attened and seen more face
on than equator on During each episo de the envelope grows from an optically
thick pseudophotosphere to a more extended and optically thin envelope
Existence of much smaller episo des of light brightening which can have the same
cause though on a more limited scale has clearly b een demonstrated
The amplitude of the d RV curve varies on a time scale somewhere b etween
and d
The following conclusions are less certain and represent p ossible alternatives to b e
tested by future systematic and homogeneous observations
Some evidence is presented that the amplitude of the d RV variations
lo cal mean RV and brightness of the ob ject prewhitened for the long term
changes all vary on a time scale of ab out d p ossibly with a p erio d of
d
The O C deviations of the lo cal ep o chs of RV maxima from a linear ephemeris for
the d p erio d seem to b e undergoing a slow and probably cyclic variation
in time b eing shortest at times when the star is brightest and when a new
Be envelope b egins to grow However the same O C deviations can also b e
reconciled with the d p erio d Whatever the true timescale of the O C
deviations is their b ehaviour can also b e simulated as an interference of several
Be Star Newsletter
p erio ds the second most signi cant p erio d b eing close to d Several reasons
are given why the explanation in terms of one variable p erio d app ears more
probable
With the help of b oth real and arti cial data it is demonstrated that the slow
variation of the d p erio d if unrecognized may b e misinterpreted
for a multiperio dic variation with several close p erio ds b etween d and
d This constitutes a metho dological warning for the p erio d analyses of data
on some Bn Be and slowly pulsating B stars
The cause s of the variations with the and p erio d s and or the
d cycle remain unexplained It is obvious however that these three p erio ds
are not mutually indep endent The d p erio d may b e either a real physical
p erio d or a b eat p erio d b etween the d and d p erio ds In the former
case CMa could b e a d binary in an eccentric orbit and the p erio ds twice
longer than the two p erio ds near d would represent the sidereal and syno dic
rotational p erio ds of the Be primary
Finally some sp eculations are o ered in terms of a hierarchical multiple system
of three or even four stars
Investigation of the variability of bright Be stars
using Hipparcos photometry
A M Hub ert and M Flo quet
Observatoire de Paris Meudon D A S G A L URA du CNRS F Meudon Cedex France
The high accuracy and the homogeneity of Hipparcos data for bright stars have al
lowed us to quantify the degree of variability of Be stars This degree has b een found
to b e highly dep endent on the temp erature of the star Rapid variability is the main
feature of of early Be and less than of late Be stars taking into account the
limit of detection considered In addition to the Be stars rep orted in the Hipparcos
catalogue ESA as short p erio d variables we have b een able to enlarge the
number of detections as well as to con rm p erio ds previously determined Be stars
that show larger amplitude rapid variations are prop osed as candidates for a search
of multi perio dicity i e as non radial pulsators
We have also searched for the presence of outbursts and fading events in the Hippar
cos data Outbursts have b een frequently and preferentially detected in early Be stars
with rather low to mo derate V sin i while fading events seem to b e more conspicuous
in stars with higher V sin i Mid term and long term variations have also b een inves
tigated Several stars have shown some evidence of quasi p erio dic oscillations ranging
b etween and days
Finally information concerning long term variations is rep orted Cycles shorter than
or equal to the Hipparcos mission have mainly b een detected in stars earlier than B
Long term time scales of late Be stars are con rmed to b e longer by far
Be Star Newsletter
Accepted by A A
Preprints from Anne Marie Hubert obspm fr
Luminous Magnetic Rotator Theory
J P Cassinelli
Department of Astronomy UNiversity of Wisconsin N Charter St Madison WI U S A
This pap er decsrib es the development of a wind theory that combines forces asso ciated
with magnetic rotators with those op erating in line driven winds It has relevance to
cyclic variability b ecause if a rotating star has a magnetic eld that changes from one
longitude sector to the next the wind sp eed can also change and this could lead to
fast slow wind co rotating interaction region This pap er fo cuses on e ects that can
increase the radial velocity of a line driven wind within a sector
To app ear in ESO Workshop on Cyclical Variability in Stellar Winds
Preprints from cassinelli madraf astro wisc edu
Large scale p erturbations in the circumstellar
envelopes of Be X ray binaries
I Negueruela P Reig M J Co e J Fabregat
1
Astrophysics Research Institute Liverpo ol John Mo ores University Byrom Street Liverpo ol L
AF U K
2
Physics and Astronomy Department Southampton University Southampton SO BJ U K
3
Departmento de Astronomia y Astro sica Universidad de Valencia Burjassot Valencia
Spain
We investigate the sp ectroscopic characteristics of the optical comp onents of Be X
ray binary systems using data collected during our seven year monitoring campaign
We nd examples of ma jor changes in the emission line pro les asso ciated with Type
II X ray outbursts later developing into V R variability cycles We show that the
time scales for V R variability in Be X ray transients extend from a few weeks to
years and interpret all these changes as due to the presence of global disruptions of
the axisymmetric density distribution in the extended envelopes of the Be stars in
these systemes The asso ciation b etween X ray outbursts and V R variability the
o ccurrence of very fast changes and very short quasi p erio ds of variability displayed
by the Be X ray binaries lead us to conclude that the presence of the neutron star
is an imp ortant factor a ecting the dynamics of disc like envelopes The interaction
b etween the compact companion and the disc would explain the correlation b etween
H strength and orbital p erio d recently found The characteristics of the V R cycles
are however mainly indep endent of the binary parameters
A A in press
Preprints from ind staru livjm ac uk
Be Star Newsletter
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Be Star Newsletter
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Be Star Newsletter
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Be Star Newsletter
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Be Stars in Op en Clusters I I Balmer Line Sp ectroscopy
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Be Star Newsletter
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Hipparcos Photometry of Herbig Ae Be Stars
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Circumstellar Disc Variations around Pictoris
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ZHANG Z Y XIONG D R Acta Astr Sinica
Be Star Newsletter
MEETINGS
June
IAU Collo quium Variable and Non spherical Stellar Winds in
Luminous Hot Stars
Heidelb erg Germany
http www lsw uni heidelberg de iaucoll
August September
Variable Stars as Imp ortant Astrophysical Tools
Izmir Turkey
asi http sci ege edu tr nato
November
IAU Symp osium Wolf Rayet Phenomena in Massive Stars and
Starburst Galaxies
Puerto Vallarta Mexico
http www astro ugto mx eenens hot pv
June July
The Be Phenomenon in Early Type Stars
Alicante Spain
http www chara gsu edu BeNews Issue alicante html
See http cadcwww dao nrc ca meetings meetings html for more
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it Preprints from tt YOUR ELECTRONIC ADDRESS
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