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Georgia State University Department of Physics and Astronomy Center for High Angular Resolution Astronomy Atlanta, Georgia, 30303-3083

This report covers the period 1 July 1993 through 30 June Laura R. Penny, Lewis Roberts, Jon Sowers, Michelle L. 1995. Thaller and Nils H. Turner. The following students joined the graduate program in this period: Liu Ning, Reed Riddle, and Xiong Ying. Fu received his Ph.D. and is now on the faculty 1. PERSONNEL at National Taiwan Normal University. Frazin joined the Astronomy faculty in the Department of Physics and As- Ph.D. program in Astronomy at the University of Illinois tronomy were Ingemar K. Furenlid, Douglas R. Gies, Donald after receiving his M.S. degree. Upon the award of his Ph.D., H. Gudehus, Harold A. McAlister ͑CHARA Director͒,H. Mangalam accepted a post-doctoral associateship at the Uni- Richard Miller, Paul J. Wiita, and David W. Wingert. versity of Illinois. Riddle spent three months as a summer Stephen Ridgway has a half-time appointment as a CHARA research assistant at the National Solar Observatory. visiting scientist along with his primary appointment as As- Long–term visitors included N. Carleton ͑Harvard- tronomer at NOAO. Staff scientists and post-doctoral fellows Smithsonian CfA͒, S.K. Chakrabarti ͑Tata Inst. Fundamental within CHARA were William G. Bagnuolo, Jr., Theo ten Research͒, F. Fekel ͑Tennessee State U.͒, Gopal-Krishna Brummelaar; William I. Hartkopf, and Brian D. Mason; John ͑NCRA͒, V. Krishan ͑IIA͒, D. Saikia ͑NCRA͒, and W.-S. W. Wilson was the Coordinator of Laboratories, Alexandra Tsay ͑National Central University, Taiwan͒. The University Land was the CHARA business manager, and Molly Raby Center in Georgia Visiting Scholars for 1994 and 1995 were was Astronomy Secretary. Margaret Burbidge ͑UCSD͒ and Shri Kulkarni ͑Caltech͒, re- Ingemar Furenlid passed away on 11 February 1994 while spectively, and a College of Arts and Sciences Distinguished on sabbatical at the Harvard–Smithsonian Center for Astro- Lecturer for 1994 was Owen Gingerich ͑Harvard͒ whose ad- physics ͑cf. BAAS vol. 26, p. 1603, 1994͒. Gies was pro- dress was presented in memory of Ingemar Furenlid. moted to Associate Professor with tenure in September 1994, and was given the 1993 College of Arts and Sciences Out- standing Junior Faculty Award. Gies acted as Technical Edi- 2. HARD LABOR CREEK OBSERVATORY tor for the paper and electronic versions of the Be Star News- Hard Labor Creek Observatory is operated by Georgia letter for issues 28–30 ͑URL http://www.chara.gsu.edu/ State University and houses the 30Љ Beck telescope of Agnes BeNews/intro.html͒. Gudehus, previously of Oklahoma State Scott College, the 16Љ KPNO telescope which was awarded University, was appointed as Visiting Assistant Professor in to Georgia State University by the National Science Founda- September 1993. Mason remained as a post-doctoral research tion through a grant to CHARA, and the Multi–Telescope associate in speckle interferometry after receiving his Ph.D. Telescope ͑discussed below͒. The observatory hosted 16 in December 1994 from GSU. McAlister served as Chair of public nights during 1993–95 as part of an agreement with the Kitt Peak Users’ Committee through December 1993, as the Georgia Department of Natural Resources which allowed Chair of the AAS Warner/Pierce Prizes Committee for 1994 GSU to locate the observatory on the grounds of Hard Labor and continues as a member of the JPL New Millenium Sci- Creek State Park. Well over 1000 visitors attended these pub- ence Working Group. Miller returned from a two year leave lic nights. In addition, the observatory has hosted a number of absence as a Senior Program Scientist with the UV/Visible of amateur astronomy gatherings sponsored by CHARA. Branch of the Astrophysics Division at NASA/HQ in Wash- The refurbishment and upgrading of the Beck Telescope ington, D.C. in September 1994; he received NASA Group continues. A number of major improvements remain to be Achievement Awards and DARA and NASA Recognitions completed, so it is not certain when this telescope will be for Individual Merit for the ORFEUS-Astrospas Shuttle Mis- brought into routine operation. A Research Corporation grant sion and for the 1st Hubble Servicing Mission. Ridgway provided for our purchase of a Photometrics, Ltd. CCD cam- joined the CHARA staff as Technical Manager of the era and associated electronics, including a Macintosh micro- CHARA Array project in December 1994. Wiita was pro- computer for its control, which we have installed at the 16Љ moted to Professor in September 1993 and succeeded McAl- telescope at HLCO. ister as Director of Graduate Studies in Astronomy in Sep- Bagnuolo, Barry, Furenlid, and Gies designed and built an tember 1994; he spent two months as a Visiting Professor at inexpensive ͑about $80 K͒ 1-meter class spectroscopic tele- the Indian Institute of Astrophysics ͑IIA͒ and the National scope and a fiber-fed spectrograph, that achieved ‘first stellar Centre for Radio Astrophysics ͑NCRA͒ in India. Mark A. spectra’ in October, 1994. This project was funded by grants Shure, of the University of Hawaii, accepted an offer of an from NSF and Georgia State, with donations in materials and Associate Professorship, effective September 1995. labor from Georgia Tech and from volunteer Harry Gelblat, a Our continuing graduate students during this period were local contractor. This novel instrument consists of nine Donald J. Barry, Richard A. Frazin, Hsieh-Hai Fu, Kenneth 33.3-cm mirrors on a single mount, each of which feeds an Guyton, Michael E. Hahula, Jagbir S. Hooda, Minhwan f/11 beam to a 100-micron optical fiber at prime focus via a Jang, Arun V. Mangalam, Brian D. Mason, John C. Noble, Barlow lens. A control system maintains the pointing of each GEORGIA STATE UNIVERSITY 151 individual mirror. The spectrograph, implemented by Barry, served. In order to obtain measurements of very high accu- is based on the Ebert-Fastie design of Furenlid and Cardona racy, a double-slit mask has been constructed for the Hooker but includes ‘‘Newtonian’’ folding mirrors and a spherical telescope. Work on the series of speckle measurements of camera/collimator to yield an isotropic point spread function binary stars resulted in two measurement papers ͑Bright across the field of view for improved radial velocity results. Stars and Kitt Peak measurements͒ being published in this The dedicated availability of the one-meter collecting area period, and six others in process ͑White Dwarfs, Lowell Ob- and the stability of the fiber-fed bench-mounted spectrograph servatory measurements, Cerro Tololo, O stars, Occultation make the Multi–Telescope Telescope ͑MTT͒ attractive for a stars, and Mt. Wilson measurements͒. The primary partici- number of interesting projects. pants in this effort were Hartkopf, Mason and McAlister. The MTT was inaugurated with an international week- Mason, Gies, Hartkopf, McAlister, and colleagues are long observing campaign of the Be star ␭ Eridani coordi- close to the completion of a speckle survey of over 200 Ga- nated by Ryuko Hirata in November, 1994. Since that time it lactic O stars with VϽ8 to determine the frequency of bina- has been used in an extensive phase-diverse observing cam- ries with angular separations of 0%03–1Љ ͑complete except paign of Plaskett’s star which has produced, via tomographic for 44 southern objects͒. Some 13 new O-binaries have been reconstruction, separated spectra of the component stars, and discovered so far. The scientific goals are: ͑1͒ find candidates permitted detection of abundance anomalies and improved for mass determination, ͑2͒ measure the binary frequency to physical elements for this interesting system. A number of better understand the influence of binaries on O star dynam- other Be stars have been monitored for line profile variability ics, and ͑3͒ aid interpretation of composite spectrum objects. ͑LPV͒ as part of a long-term study by Gies. Hartkopf and Combined speckle/spectroscopic orbits offer the potential for Gies have begun a radial-velocity program to complement direct measurement of mass. First results from this survey ongoing CHARA speckle interferometric work, which has have already bridged the period gap between astrometric and already resulted in the detection of a third spectral compo- spectroscopic binaries for 15 Mon producing the first com- nent in the 55 UMa system. Bagnuolo and Barry continue an bined spectroscopic/astrometric O-star orbit. New spectro- intensive program to gather separated spectra of binary sys- scopic and astrometric ͑HST/FGS͒ observations are planned tems via the application of tomographic techniques to re- as this system progresses to periastron in 1998. The derived solve blends through phase-diverse observations. Barry has binary frequency itself is an important result of the survey extended this program with echelle spectroscopy on the 82Љ since binaries can affect the dynamical evolution of clusters at UT Austin’s McDonald Observatory, and the MTT will be through gravitational encounters. Ejected stars should be de- used to gather information on narrower passbands and to pleted in binaries, and indeed all the new binaries are mem- complete phase coverage on the numerous systems which do bers of clusters and associations. Finally, speckle observa- not present convenient phases during prescheduled block ob- tions will aid significantly in identification and interpretation serving on major telescopes. of composite spectrum objects. Both graduate and undergraduate students have been An additional goal of these observing runs was the survey trained in spectroscopic observation using this facility, and of occultation binaries. This program also nears completion we expect it to become even more heavily utilized during the and has resulted in the first resolution of two dozen binary coming year. Bagnuolo is supervising an upgrade to several systems and new orbits for seventeen systems. Analysis of major systems scheduled during the coming year, which will these occultation systems was the subject of the dissertation improve tracking stability through replacement of the shaft of Mason. reduction gears with a stiffer arrangement, improve acquisi- A major program of speckle observations was carried out tion and tracking magnitudes significantly with a new inten- at the Lowell Observatory 1.8-m from 1982 through 1988 as sified camera, and improve blue sensitivity through substitu- part of a search for low-mass companions to known binary tion of a thinned back-illuminated CCD in the existing systems. Otto Franz ͑Lowell Obs.͒ collaborated on the acqui- detector assembly. sition of those data. A large portion of these data, reduced by ex-graduate student Ali M. Al-Shukri ͑now at the King Fahd 3. CENTER FOR HIGH ANGULAR RESOLUTION University of Petroleum and Minerals in Dhahran, Saudi ASTRONOMY Arabia͒, were published by Al-Shukri, McAlister, Hartkopf, CHARA activities center around our on-going program of and colleagues as the first in a series of papers describing the binary star speckle interferometry and the development of a results of this effort. Fu completed a dissertation based upon multiple-telescope long-baseline optical interferometer – the the analysis of another subset of these data. CHARA Array. Experiments are also continuing at Mt. Wilson on the The speckle program conducted observing runs at the 100Љ telescope by Roberts, ten Brummelaar, Bagnuolo, CTIO 4-m in April 1994, the KPNO 3.8-m in September Turner and Mason in non-redundant aperture masking for the 1994, and the CFHT in November 1994. Over 1000 obser- purpose of obtaining high angular resolution and differential vations were obtained on these observing runs. In late 1993, photometry of close binary stars. This program will continue a program was also initiated at the 2.5-m Hooker telescope at both at Mt. Wilson and on the HLCO 0.4-m telescope. Mag- Mt. Wilson, and we were the first visitors to use the refur- nitude difference determinations were also investigated with bished telescope since its opening was announced by the the Starfire Optical Range ͑SOR͒ 1.5-m telescope in May Mount Wilson Institute. As part of a continuing program to 1995. Reduction of these data is in progress. observe close binary stars nearly 2000 stars have been ob- ten Brummelaar has continued his research into wave 152 ANNUAL REPORT propagation through a turbulent atmosphere, including the ing design issues, as the optical path length—a parameter use of several nights observation time at SOR. The data col- which is usually neglected in astronomy—must be controlled lection process has been refined to the point where it does and stabilized, and the mount is somewhat more robust than not interfere with normal observations and is now being done typical of 1-m telescopes. Control of focus, tilt and optical in parallel with the differential photometry experiments at figure are also particularly important, and various aspects of SOR. This data will help in studies of the atmosphere’s effect the design address these concerns. on fringe visibility as well as the use of adaptive optics in a Extensive information concerning the CHARA Array is stellar interferometer. available on a continuously updated basis on our WWW Work by McAlister et al. made further investigations homepage ͑http://www.chara.gsu.edu/͒, and we refrain from among binary properties and statistics of bright stars. This giving an extensive account here. We include in our bibliog- led to the discovery thirty-two binaries and detailed studies raphy a list of CHARA Technical Reports describing various of the O star binary 15 Mon by Gies et al. and the nearby aspects of the project. multiple system ␰ Ursae Majoris by Mason et al. Penny, Bagnuolo, Barry, and Gies are pursuing a program Joel Eaton ͑Tennessee State U.͒, Hartkopf, McAlister, and of re-constructing the individual spectra of the components Mason collaborated on a study of winds in the ͑M2 Ib-II ϩ of massive binary systems using a tomography algorithm. B9.5 V͒ close binary system ␦ Sge. Masses, radii, and other This method is an iterative scheme that uses the velocity properties were determined for both components. Evidence curves of both components and an assumed intensity ratio to suggests both a low-speed wind from the M supergiant and a determine the spectrum of each star from an ensemble of high-speed wind from an accretion disk around the B dwarf. Doppler-shifted, composite spectra. The separated spectra A collaboration with Frank Fekel ͑Tennessee State U.͒, can be examined to determine the spectral types and lumi- Phil Ianna ͑U. Virginia͒, Andrei Tokovinin ͑Moscow U.͒, nosity classes, the projected rotational velocities, a magni- Roger Griffin ͑Cambridge U.͒ and Roger Culver ͑Colorado tude difference estimate, and, potentially, chemical abun- State U.͒ was completed regarding the nearby speckle/ dance differences. spectroscopic/astrometric binary HR 6697. The method is being applied to IUE high-dispersion spec- Work continues by McAlister et al. investigating a small tra of some 35 O-type binary systems. Penny has devised sample of white dwarf binaries with an emphasis on HZ 43 general schemes for spectral classification and measurement and GD 319. of rotational velocities in the UV for O stars. She has also Hartkopf et al. obtained orbit solutions for thirty-seven developed cross-correlation methods for accurate radial ve- visual/interferometric systems. Further work on orbits con- locity measurements of IUE spectra of double-lined binaries. tinues with that of McAlister et al. investigating Hyades bi- The goal is to establish the location of the individual stars in naries, Hartkopf et al. regarding combined solution systems, a theoretical HR-diagram in order to test current models of and by Mason et al. investigating occultation binaries, the binary evolution for massive stars. nearby solar-type visual/spectroscopic binary Fin 347, and Many of these same O-binaries have been observed by the O star binary HD 193322. Ongoing collaborators on Barry during the first year of spectroscopic observations with these projects include Gies, Fekel, Griffin, and Colin Scarfe the GSU MTT. Bagnuolo and Barry have performed a tomo- ͑U. Victoria͒. graphic separation of the components of Plaskett’s star ͑HD The CHARA speckle program continued to be supported 47129͒ using MTT spectra which confirm that the secondary by the National Science Foundation. is a rapidly rotating O-supergiant. The MTT has also been United States Senator Sam Nunn of Georgia announced in used for a tomographic study of the speckle triple 55 UMa a press conference on the GSU campus on 25 October 1994 ͑by Liu, Xiong, Riddle, Barry, Bagnuolo, and Gies͒ and line that the National Science Foundation was awarding $5.6M to profile studies of selected Be stars ͑Barry and Gies͒. GSU towards the construction of a five-telescope interferom- Thaller and Gies are using the same set of IUE spectra of eter with submilliarcsecond resolution at visible wavelengths massive binaries to explore the orbital phase-related varia- and milliarcsecond resolution at K-band. The University has tions in the stellar wind lines to search for evidence of col- committed itself towards providing as matching funds the liding winds. In addition, they have obtained H␣ spectra of remaining costs of this facility, estimated to total $11.4M. these systems to study the recombination emission ͑formed This announcement culminated nearly a decade of activity in high density regions͒ from colliding winds. on the part of CHARA to obtain the financial resources to Thaller, Bagnuolo, Gies, and Penny have applied the to- complete this flagship goal of the Center. The Array will be mography algorithm to IUE spectra of the Be binary ␾ Per located on Mt. Wilson, the site at which interferometry was which led to the discovery that the secondary is a hot pioneered in this country, and we anticipate operation of the subdwarf, the stripped-down remains of the mass loser in facility by the end of the decade. this binary. This system fills the missing link in the evolu- Ridgway and other CHARA staff worked with mechanical tionary sequence between main sequence massive binaries engineering consultant Larry Barr on the optical and me- and Be plus neutron star binaries, and it may represent the chanical specification and design of the telescopes for the class of progenitors of Type Ib or Ic supernovae. A similar CHARA Array. The telescopes are afocal, acting as 8:1 beam study is underway ͑with G. Peters, USC͒ on the Be binary compressors. The mounts are alt-az, with a 6-mirror coude´ HR 2142. transferring the compressed beam to a fixed axis for redirec- Investigations at HLCO by Mason, Roberts, and Barry tion to the central laboratory. The telescopes present interest- continue on the galactic cluster Collinder 419. Work was GEORGIA STATE UNIVERSITY 153 initiated on the visual/spectroscopic Cepheid binary ADS the rate of angular momentum evolution; these results have 14859 by Mason in collaboration with Nancy Evans ͑SAO͒, applications to low mass X-ray binary systems. Dick Walker ͑Naval Obs.͒, Franz, and Derck Massa ͑Applied Sowers and Gies are completing a study of the H␣ emis- Research Corp.͒. sion in the massive X-ray binary Cygnus X-1. Preliminary Hartkopf has created a Double Star Library on the WWW results suggest that the emission arises in the base of the ͑URL http://www.chara.gsu.edu/ DoubleStars /intro.html͒ stellar wind of the O-supergiant primary and in the focused which contains information on IAU Commission 26 ͑Binary wind flow to the black hole companion. and Multiple Stars͒, bibliographic data, and spectroscopic In an updated study of the population II binary ␮ Cas, and astrometric catalogs. Gudehus has obtained improved mass estimates of the com- ponents. As part of this study, he has developed software 4. STELLAR ASTRONOMY which permit a combined solution of astrometric, speckle, and spectroscopic multiple star data. Besides the 2 main Gies, Roberts, and David Lambert U. Texas at Austin ͑ ͒ components, up to 10 spectroscopic subcomponents can be are using HST/GHRS and IUE spectra to study boron abun- included in the simultaneous solution. dances in Orion B stars. The Orion OB1 association com- Wilson has written a series of four new astronomy labo- prises four subgroups of differing ages. The youngest stars ratory exercises. One of these involves piggyback photogra- show higher oxygen abundances than do the oldest stars. phy and three are computer simulations using purchased This enrichment has been shown to be due to contamination software. These will be published in a second edition of ‘‘As- of the natal gas by oxygen-rich ejecta from supernovae. The tronomy: A Laboratory Textbook.’’ boron abundance is being derived from the B II 1362 Å line Gies, J. Purcell, Wilson, and Wingert were awarded GSU for stars in the Orion OB1 association having different oxy- Quality Improvement Funds to purchase a laptop computer gen abundances. A positive correlation of the boron and oxy- for use in classroom demonstrations and three computers for gen abundance will, if present, indicate that boron, as 11B, is use in our Astronomy Laboratories. synthesized by the supernovae held responsible for the oxy- gen abundances. This will be the first direct evidence for 11B production by supernovae. Gies and Hahula collaborated in several projects on the 5. EXTRAGALACTIC ASTRONOMY rapid profile variations found in O- and B-type stars. The Miller and co-workers continue their program investigat- periodic component of variability is probably the result of ing the very rapid low amplitude variations in the optical and photospheric nonradial pulsations ͑NRP͒ that can re- ultraviolet portions of the electromagnetic emission from ac- distribute the flux in a rotationally broadened profile through tive galactic nuclei ͑AGN͒. This group was the first to show the creation of sectors of differing velocity and temperature that microvariability was both real and common, at least for in the visible hemisphere of the star. Gies and Hahula have the blazar class of AGN ͑BL Lacertae objects and Optically participated in several multi-wavelength campaigns on the Violently Variable Quasars͒. Over the past three years they line profile variability in Be stars. In this group of rapid have discovered similar rapid fluctuations in Seyfert galaxies rotators, it is possible that NRP help promote mass loss into and have recently shown that some radio quiet quasars a dense circumstellar envelope that produces Balmer emis- ͑RQQSOs͒ exhibit similar optical variability. In collabora- sion lines. New campaigns have been undertaken on EW Lac tion with Wiita and co-workers, they have investigated a and ␣ Eri which involved UV spectroscopy with IUE ͑Pe- wide range of astrophysical models for these variations. ters, USC; Henrichs, U. Amsterdam͒, optical photometry Both Jang and Noble reached the final stages of their dis- ͑Percy, U. Toronto͒, optical polarimetry ͑McDavid, Limber sertation work under Miller’s supervision during this period. Obs.͒, and optical spectroscopy from KPNO ͑Gies and Noble has obtained data utilizing the 42Љ telescope at Lowell Hahula͒ and Mt. Stromlo Observatory ͑Thaller͒. Almost all Observatory, the 0.9-m telescope at Kitt Peak National Ob- these targets display variations consistent with the presence servatory, and the 0.9-m telescope at Cerro Tololo Inter- of a low-order (lϭ2) mode of NRP but other non-periodic american Observatory during twelve observing runs and dis- variations are also present. The same periods are found in the covered the most rapid optical variations ever detected for UV wind lines which suggests that NRP modulates mass loss the Seyfert galaxy Akn 120; these results place very tight in Be stars. constraints on the size͑s͒ of the emitting region͑s͒, and Guyton and Gies are constructing models for line profiles strongly suggest that these variations are independent of the in rapidly rotating hot stars. They intend to apply these mod- radio properties of AGNs. Noble has also obtained observa- els to search for latitude-dependent line formation in such tions of three blazars, AO 0235ϩ164, 0323ϩ023, and 4C rotators and to help determine how such stars can be spun up 29.45, when these objects were in a faint state. In each case, to the critical rotation rate. unusually rapid and large-amplitude events were detected. Bhaskar Datta, Arun Thampan ͑IIA͒ and Wiita have cal- This strongly suggests that the microvariability is much more culated accretion disk and surface layer luminosities for ac- pronounced when these objects are in a faint state than when cretion onto neutron stars possessing weak surface magnetic they are in a bright state. This is consistent with these varia- fields. They also considered the related problem of angular tions being produced as the result of discrete disturbances in momentum evolution of such neutron stars and made esti- the accretion disk. Noble has obtained observations for ap- mates of the accretion driven change in angular momentum. proximately 20 additional bright x-ray selected blazars. On Rotation always increases the disk luminosity and reduces average, the variations observed for these blazars are less 154 ANNUAL REPORT violent and are thus consistent with the x-ray selected blazars disk atmospheres can yield very rapid changes in polariza- being less beamed and with lower Lorentz factors than the tion for radio emission from AGN. While this process is radio-selected blazars. probably unlikely to dominate polarization variations, reso- Jang has completed a program to investigate the nature of nance absorption may yield very rapid, low amplitude varia- the microvariability in radio quiet ͑RQ͒ and radio loud ͑RL͒ tions. Seyfert galaxies and quasars, using the 30ЈЈ telescope at Chakrabarti and Wiita considered the effects of spiral Rosemary Hill Obs. ͑U. Florida͒ and the 42ЈЈ telescope at shocks in accretion disks upon the shapes of spectral lines Lowell Observatory. A small number of the RQQSOs have arising from the disks. Spiral shocks could be induced by a exhibited mild microvariability, while the detection of micro- binary companion or passing massive star ͑in the case of variability for the RLQSOs is quite common, and compa- AGN͒ and these line signatures may be the only way in rable in frequency to that of blazars. These observations pro- which the shocks may be observed. The spectra of some vide an important insight into the origin of the AGN which exhibit varying two-horned broad emission lines microvariations, indicating that many short-term optical fluc- can be explained if spiral shocks are present and general tuations are related to the same phenomena that engender relativistic effects produced by supermassive black holes are fast radio variability. incorporated in the calculations. Hydrodynamical simula- A related search for optical microvariability in more lu- tions by Chakrabarti and Wiita indicated that rapid minous radio quiet QSOs has been undertaken by Gopal- optical/UV variability in some AGN may arise from this Krishna, Ram Sagar ͑IIA͒, and Wiita. Of the first 13 objects mechanism. examined, 5 showed strong indications of microvariability, Gudehus has studied the Virgocentric motion by using and 3 others showed some hint thereof. For only one of this several different relative distance indicators thought to be sample can an extremely strong claim of optical intra-night free of systematic effects. These include average nuclear variability be claimed, and it ͑0838ϩ359͒ is the only source magnitudes of the ten brightest galaxies in a cluster corrected that has weak, but non-trivial, radio emission. In that clear for richness, and reduced galaxian radius parameters. When cases of optical fluctuations from radio silent AGN would used with the global solution method, these yield a Virgo indicate the probable detection of accretion disk fluctuations, infall velocity of 52Ϯ67 km sϪ1. Gudehus also finds very this monitoring program continues at the Vainu Bappu Ob- good agreement of the projected radial motions of Virgo and servatory, Kovalur, India. Hydra I from this study and their independently measured Our observational studies of microvariability are being radial peculiar velocities. In addition, the Virgo peculiar mo- expanded in several ways so that we can investigate the pos- tion agrees with a simulation of peculiar motions arising in a sibility that the character of the variations at different states dark matter dominated expanding universe. for each blazar might be different, and determine if the char- Gudehus is continuing to investigate cluster galaxy dy- acter of the variations are different for blazars which may be namical and luminosity evolution by analyzing two-band ex- x-ray selected versus radio selected. A larger sample of posures made with his imaging CCD system. In connection radio-quiet quasars are being studied in order to more fully with this work he has developed an enhanced version of study the differences between radio-loud and radio-quiet SAOimage along with a set of modules that allow easy ex- quasars. We will observe more blazars, Seyfert galaxies, Ra- ternal control of this pseudocolor display program. The soft- dio Loud QSOs, and RQQSOs so as to obtain statistically ware, along with the MIIPS package, has been made avail- valid indications of the differences between the prevalence able via anonymous ftp. and strength of microvariability. Multi-color observations of Numerical simulations of extragalactic radio jets contin- a few individual objects will also be performed. HLCO pro- ued, with Hooda, Mangalam and Wiita having completed a vides us with the ability to make long-term studies of a series of high-resolution two-dimensional hydrodynamical smaller number of bright sources as well as to produce a models carried out to the longest distances ever reported. complete survey of a uniform sample. These types of obser- These axisymmetric jets eventually disrupt via Kelvin- vations will provide data necessary to discriminate between Helmholtz instabilities, and detached lobes of plasma will the various more detailed theoretical models for rapid vari- produce fading extended radio sources. If the nuclear source ability on which we, and many others, are currently working. remains energized, however, the nearer part of the jet sur- As a key example, our evidence of microvariability in RQQ- vives and new hot-spots appear closer to the nuclear region. SOs strongly supports models where some of the variability Hooda and Wiita have recently turned to modelling jets in is based upon flares or shocks on disks. But many more three-dimensions, breaking axisymmetry by having the jets sources must be observed for longer periods to establish the cross an angled interface between an interstellar medium and nature of such microvariability and that of its possible differ- a hotter, lower-density, intracluster medium. This induces ences from that seen in radio loud AGN. wiggles, but no large scale bending, in the jets; towards the Several plasma processes that might contribute to vari- end of the preliminary simulations, significant non-linear ef- ability on wide ranges of temporal scales have been consid- fects, including apparent twisting and bifurcation of the jet ered by Vinod Krishan ͑IIA͒ and Wiita. Flare processes in appear. To investigate these key results further, higher reso- accretion disk coronae show particular promise, and more lution simulations are in progress. detailed calculations, including predicted polarization ef- In collaboration with several Indian colleagues at NCRA, fects, are underway. Krishan and Wiita have argued that reso- Wiita and Mangalam have considered statistics and models nance absorption in broad line region clouds or accretion of radio galaxies, with a particular emphasis on testing uni- GEORGIA STATE UNIVERSITY 155

fied models for AGN. A popular unification scheme has built telescope which is mounted on the free–flying space radio-loud quasars as a subset of radio galaxies whose jets platform, Astrospas. Far and extreme ultraviolet spectro- are viewed at smaller angles to the line of sight, and blazars graphs are mounted on the telescope providing a spectral as a smaller group viewed at excellent alignment. A key ob- coverage from 400–1200 Å . This mission provides an early, jection arises from recent studies which indicate that the rela- limited look at the 900–1200 Å spectral region which will be tive counts and median radio sizes of quasars and radio gal- investigated by FUSE, which is scheduled for launch in axies at lower-redshifts do not match those expected from 1998. As part of NASA’s support of this effort, Miller will the simple orientation based scenario. Gopal-Krishna, V.K. participate in the observational programs carried out by OR- Kulkarni and Mangalam showed that if the angle of the ob- FEUS. Georgia State University will serve as the principle scuring torus was slightly misaligned with the jet direction site for all educational efforts related to the ORFEUS mis- this inconsistency can be relieved. We have recently found sion. that incorporation of temporal evolution in radio source size and radio power can also naturally remove this apparent dif- 7. SUPPORT ficulty ͑Gopal-Krishna, Kulkarni and Wiita͒. Another objec- During this period, astronomical research at Georgia State tion to the unified picture notes the significantly different University has been supported by the National Science Foun- VLBI polarization properties of BL Lacs and quasars. Gopal- dation, the National Aeronautics and Space Administration, Krishna and Wiita showed that this difference can be ex- the Smithsonian Institution, the Research Corporation, and plained by allowing for contributions to the observed syn- the Pittsburgh Supercomputing Center. We have greatly ben- chrotron emission from both the shock compressed plasma efited from the facilities of the National Optical Astronomy and post-shock expanding plasma; this fits in nicely with Observatories, Lowell Observatory, Mount Wilson Observa- certain unification scenarios. Saikia, S. Jeyakumar ͑NCRA͒, tory, Rosemary Hill Observatory, and the Vainu Bappu Ob- Wiita, H. Sanghera ͑Dwingeloo͒, and R. Spencer ͑Jodrell servatory. We are also grateful for funds from the Vice Presi- Bank͒ analyzed a sample of Compact Steep Spectrum radio dent for Research, the Dean of the College of Arts and galaxies and quasars. They showed that lobe-size and flux Sciences, and the Board of Regents of the University System density ratios, as well as misalignment angles, were all basi- of Georgia. cally consistent with the unified scheme; however, intrinsic asymmetries, presumably arising from the greater relative PUBLICATIONS importance of interactions with non-uniformities in the con- Al-Shukri, A.M., McAlister, H.A., Hartkopf, W.I., Hutter, fining medium for smaller sources play an important role as D.J., & Franz, O.G., ‘‘ICCD Speckle Observations of Bi- well. Both analytical and numerical models of these CSS nary Stars. XII. 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