DOCSLIB.ORG

Atmospheric Activity in Red Dwarf Stars

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Atmospheric Activity in Red Dwarf Stars CONTENTS SUMMARY AND CONCLUSIONS PAPERS ON CHROMOSPHERIC LINES IN RED DWARF FLARE STARS I. AD LEONIS AND GX ANDROMEDAE B. R. Pettersen and L. A. Coleman, 1981, Ap.J. 251, 571. II. EV LACERTAE, EQ PEGASI A, AND V1054 OPHIUCHI B. R. Pettersen, D. S. Evans, and L. A. Coleman, 1984, Ap.J. 282, 214. III. AU MICROSCOPII AND YY GEMINORUM B. R. Pettersen, 1986, Astr. Ap., in press. IV. V1005 ORIONIS AND DK LEONIS B. R. Pettersen, 1986, Astr. Ap., submitted. V. EQ VIRGINIS AND BY DRACONIS B. R. Pettersen, 1986, Astr. Ap., submitted. PAPERS ON FLARE ACTIVITY VI. THE FLARE ACTIVITY OF AD LEONIS B. R. Pettersen, L. A. Coleman, and D. S. Evans, 1984, Ap.J.suppl. 5£, 275. VII. DISCOVERY OF FLARE ACTIVITY ON THE VERY LOW LUMINOSITY RED DWARF G 51-15 B. R. Pettersen, 1981, Astr. Ap. 95, 135. VIII. THE FLARE ACTIVITY OF V780 TAU B. R. Pettersen, 1983, Astr. Ap. 120, 192. IX. DISCOVERY OF FLARE ACTIVITY ON THE LOW LUMINOSITY RED DWARF SYSTEM G 9-38 AB B. R. Pettersen, 1985, Astr. Ap. 148, 151. Den som påstår seg ferdig utlært, - han er ikke utlært, men ferdig. 1 ATMOSPHERIC ACTIVITY IN RED DWARF STARS SUMMARY AND CONCLUSIONS Active and inactive stars of similar mass and luminosity have similar physical conditions in their photospheres/ outside of magnetically disturbed regions. Such field structures give rise to stellar activity, which manifests itself at all heights of the atmosphere. Observations of uneven distributions of flux across the stellar disk have led to the discovery of photospheric starspots, chromospheric plage areas, and coronal holes. Localized transient behavior has been identified in both thermal and non-thermal sources, such as flares, shock waves and particle acceleration. The common element to all active regions is the presence of strong magnetic field structures connecting the violently turbulent deep layers in the convection zones of stars with the tenuous outer atmospheres. Transport and dissipation of energy into the chromospheric and coronal regions are still much debated topics. PROPERTIES OF STELLAR FLARES A stellar flare is observed as an increase in radiation from all levels of the stellar atmosphere. In addition to a very strong optical and ultraviolet continuum, one detects X-rays and radio waves from the corona and emission lines from the transition region and the chromosphere. Continuum dominates over radiation losses in emission lines during the phase of maximum radiation. In contrast, the "white light" continuum is rarely seen in solar flares. The optical flare event is characterized by a rapid increase in brightness, often followed by an almost equally rapid decay, but the main part of the duration of a flare is taken up by a slow decay in brightness till the pre- flare level is again reached. Many parameters of the flare light curve vary by two orders of magnitude on the same star, such as timescales of rise and decay, and the flare amplitude. The total energy emitted in optical light during a flare varies by much more. On some stars we detect flares as small as IO*7 ergs. The largest events have emitted in excess of 1035 ergs. The flux at maximum spans more than four orders of magnitude. The frequency distributions of flare energy ,^jrshberg 1972) and flux at flare maximum (Kunkel 1973) demonstrate that large flares, both in terms of energy and amplitude, are much less common than small flares. As the technical ability to detect smaller flares has improved over the years, it has been demonstrated that the distributions continue to hold. There is no indication yet of "a smallest possible flare", below which no flare event is recorded. Numerical values for the slope of the cumulative frequency distribution of flare energy vary from star to star. It is not clear if this is a property of the star, or if it is due to observational effects. In Fig. 1, which compiles distributions for a number of stars, it appears a collective property that all stars have similar slope values. For solar neighbourhood stars the values range from 0.4 to 1.0, and show some tendency of correlation with stellar luminosity. T 1 i i r log Ey (ergs) 34 32 30 28 26 i • I 1 1 l 1 i -6 -4-2 0 +2 log N/T (hour"') Fig. 1. - Cumulative frequency distributions of flare energy for a number of stars. Photometric observations of flares have revealed a number of statistical properties of flare activity on stars. Some are due to observational selection effects connected to the contrast between flare light and the photospheric brightness. Energetic flares are seen mostly on intrinsically bright stars, while low energy flares are seen on faint stars. Since small flares occur more frequently than large flares we observe that intrinsically faint stars flare more often than bright stars. The relative contribution of flare light to the total flux from a star is larger in faint stars than in bright ones. The low energy cut-off as a function of stellar luminosity is apparent in Fig. 1. Whether low luminosity stars are capable of producing very energetic flares cannot be decided from existing observations. Such stars must be observed with large telescopes where observing time is precious, so only a few hours of monitoring have been accumulated on most of these objects. The bright stars can be observed with small telescopes and require vast amounts of observing time for each detected flare. Since the sampling times are so different, the conditions favour detection of very energetic flares in bright stars. It may be indicative, however, that 95 hours of U-filter monitoring on YY Gem (Mv°9) revealed flares as large as 1034 ergs, while 93 hours on W Cet (^=15) resulted in none larger than 5 1031 ergs. The opposite question, whether all stars produce low energy flares, cannot be investigated with optical methods due to contrast effects. Extended X-ray monitoring (and possibly in UV) would provide us with data for addressing this problem. Il When the observations are calibrated to scales of absolute physical units, the stellar luminosity in the U-filter, Ly, and the time averaged flare energy, Lj(U)( are both in ergs s"1. Total absence of low energy flares in bright stars leads to undesestiroates of their Lf(V)-values. Weaker flares can be detected in faint stars so there the sampling is more complete over the range of produced energies. Fig. 2 shows that the time averaged flare energy emitted by a star increases with increasing ste.llar luminosity. Discarding stars of unusually low activity, often with no emission lines in their spectra, we find that 2/3 Lf (U) a L„ (1) 32 1 —i 1 1— —P- log Ly • • (ergs s" ) • • / 30 m/ - • • Y - •J 28 . fa • 26 - 3 2 - Lf ' 24 —i _i _i_ ,.J i 24 26 28 30 -1, log Lf(U) (ergs s ') Fig. 2. " Time averaged flare energy for a number of stars. The observed flare frequencies are also affected by various selection effects. We have attempted to avoid these by utilizing the observed distributions of flare energy to determine the flare frequency (in flares per hour) for flares larger than a fixed value, i.e. N/T(E>EQ ergs). Since a rare large flare in a low luminosity star may be barely detectable in a bright star, we have obo£?n 29 30 Eo-10 and 10 ergs. This choice minimizes the range of extrapolation. Discarding stars of unusually low activity, we find that 1/2 (2) This relationship, which holds for five orders of magnitude in stellar luminosity, is shown in Pig. 3. Flares larger than a given energy are more frequent on bright stars than on low luminosity stars. Since this holds for several choices of energy, we suggest that in general the frequency of flares of a given energy is larger on bright stars than on faint stars. 4 it it. 09 lu - ergs s" ) • / • / • • / 30 • 30 • / . • • / • •f/• 28 28 • • • / 26 26 - / , , 24 1 b 1 1 24 —u 1 ,i i -2 0 +2 -2 0 +2 29 30 loq N/T(Eu>10 erqs) log N/T(Eu>10 ergs) (flares per hour) (flares per hour) Fig. 3. - Flare frequencies for stars of different luminosity. In summary, the results of Figs. 2 and 3 suggest that bright stars are more flare active than low luminosity stars. Theie are also indications of different activity levels for stars of similar luminosity, which may indicate that other parameters also play a role (e.g. age, rotation). Studies of flare light curves have revealed the existence of a relationship between the average flare decay rate and the luminosity of the star. An updated version of this relationship is shown in Fig. 4. It has a break near MyslO, which coincides with a similar break in the mass-luminosity relation (Pettersen 1983). For the entire luminosity range 7<MV<17 (magnitudes) one thus obtains . i 0 t. « — a <r (3) 5 °- g2 where tg.5 is the flare decay timescale, g is the surface gravity of the star, and h is the pressure (gravitational) scale height in its photosphere. For low luminosity stars (My=15) we detect flares as weak as 1027 ergs. Only rarely do we see sinole maximum flares with energies larger than 1031 ergs. The average flare decay timescale is therefore determined mainly by weak flares. Brighter stars like EV Lac and AD Leo (My»ll) have more intense photospheric radiation so the flare contrast is lower. We detect flares between 10^9 and 1Q33 ergB for these stars.
Load more

Recommended publications
  • Lurking in the Shadows: Wide-Separation Gas Giants As Tracers of Planet Formation
    Lurking in the Shadows: Wide-Separation Gas Giants as Tracers of Planet Formation Thesis by Marta Levesque Bryan In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy CALIFORNIA INSTITUTE OF TECHNOLOGY Pasadena, California 2018 Defended May 1, 2018 ii © 2018 Marta Levesque Bryan ORCID: [0000-0002-6076-5967] All rights reserved iii ACKNOWLEDGEMENTS First and foremost I would like to thank Heather Knutson, who I had the great privilege of working with as my thesis advisor. Her encouragement, guidance, and perspective helped me navigate many a challenging problem, and my conversations with her were a consistent source of positivity and learning throughout my time at Caltech. I leave graduate school a better scientist and person for having her as a role model. Heather fostered a wonderfully positive and supportive environment for her students, giving us the space to explore and grow - I could not have asked for a better advisor or research experience. I would also like to thank Konstantin Batygin for enthusiastic and illuminating discussions that always left me more excited to explore the result at hand. Thank you as well to Dimitri Mawet for providing both expertise and contagious optimism for some of my latest direct imaging endeavors. Thank you to the rest of my thesis committee, namely Geoff Blake, Evan Kirby, and Chuck Steidel for their support, helpful conversations, and insightful questions. I am grateful to have had the opportunity to collaborate with Brendan Bowler. His talk at Caltech my second year of graduate school introduced me to an unexpected population of massive wide-separation planetary-mass companions, and lead to a long-running collaboration from which several of my thesis projects were born.
    [Show full text]
  • Eine Welt Allein Ist Nicht Genug“ Großbritannien, Hannover Und Göttingen 1714 – 1837
    1 Göttinger Bibliotheksschriften 31 2 3 „Eine Welt allein ist nicht genug“ Großbritannien, Hannover und Göttingen 1714 – 1837 Herausgegeben von Elmar Mittler Katalogredaktion: Silke Glitsch und Ivonne Rohmann Göttingen 2005 4 Ausstellung in der Paulinerkirche Göttingen 20. März–20. Mai 2005 Unterstützt von: © Niedersächsische Staats- und Universitätsbibliothek Göttingen 2005 Redaktionelle Assistenz: Meike Holodiuk • Anica Rose Umschlag: Ronald Schmidt • Satz: Michael Kakuschke • Jürgen Kader Digital Imaging: Martin Liebetruth • Einband: Burghard Teuteberg ISBN 3-930457-75-X ISSN 0943-951X 5 Zum Geleit Elmar Mittler .............................................................................................. 9 Von der Manufakturstadt zum „Leine-Athen“. Göttingen, 1714–1837 Hermann Wellenreuther ........................................................................... 11 Exponate A .............................................................................................. 29 Personalunion mit England und Mitglied im Reich: Von Kurhannover zum Königreich Hannover, 1690–1837 Hermann Wellenreuther ........................................................................... 32 Exponate B .............................................................................................. 49 Britische Bilder und Vorstellungen von Deutschland im 18. Jahrhundert Frauke Geyken ......................................................................................... 52 Exponate C .............................................................................................
    [Show full text]
  • The Agb Newsletter
    THE AGB NEWSLETTER An electronic publication dedicated to Asymptotic Giant Branch stars and related phenomena Official publication of the IAU Working Group on Red Giants and Supergiants No. 276 — 1 July 2020 https://www.astro.keele.ac.uk/AGBnews Editors: Jacco van Loon, Ambra Nanni and Albert Zijlstra Editorial Board (Working Group Organising Committee): Marcelo Miguel Miller Bertolami, Carolyn Doherty, JJ Eldridge, Anibal Garc´ıa-Hern´andez, Josef Hron, Biwei Jiang, Tomasz Kami´nski, John Lattanzio, Emily Levesque, Maria Lugaro, Keiichi Ohnaka, Gioia Rau, Jacco van Loon (Chair) Figure 1: The Cat’s Eye Planetary Nebula imaged by Mark Hanson at Stan Watson Observatory with a 24′′ f6.7 teelescope. It includes 23 hours worth of [O iii]. The best known part, the “eye” is just the small object in the middle, while the messy halo extends much further. Notice also the bowshock on the right. (Suggestion by Sakib Rasool.) 1 Editorial Dear Colleagues, It is a pleasure to present you the 276th issue of the AGB Newsletter. Note that IAU Symposium 366 (”The Origin of Outflows in Evolved Stars”) has been postponed until November next year, while in June 2021 there will be a 4-week programme of workshops on stellar astrophysics in the Gaia era, in Munich (Germany). See the announcements for both meetings at the end of the newsletter. Unfortunately our proposal for a Focus Meeting at next year’s IAU General Assembly was not successful. One of the reasons given was: ”Some evaluators commented that Most of the topics in this proposal could have been made 10 or 20 years ago.
    [Show full text]
  • Durham E-Theses
    Durham E-Theses First visibility of the lunar crescent and other problems in historical astronomy. Fatoohi, Louay J. How to cite: Fatoohi, Louay J. (1998) First visibility of the lunar crescent and other problems in historical astronomy., Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/996/ Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in Durham E-Theses • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full Durham E-Theses policy for further details. Academic Support Oce, Durham University, University Oce, Old Elvet, Durham DH1 3HP e-mail: [email protected] Tel: +44 0191 334 6107 http://etheses.dur.ac.uk me91 In the name of Allah, the Gracious, the Merciful >° 9 43'' 0' eji e' e e> igo4 U61 J CO J: lic 6..ý v Lo ý , ý.,, "ý J ýs ýºý. ur ý,r11 Lýi is' ý9r ZU LZJE rju No disaster can befall on the earth or in your souls but it is in a book before We bring it into being; that is easy for Allah. In order that you may not grieve for what has escaped you, nor be exultant at what He has given you; and Allah does not love any prideful boaster.
    [Show full text]
  • Detecting Reflected Light from Close-In Extrasolar Giant Planets with the Kepler Photometer
    Accepted for publication by the Astrophysical Journal 05/2003 Detecting Reflected Light from Close-In Extrasolar Giant Planets with the Kepler Photometer Jon M. Jenkins SETI Institute/NASA Ames Research Center, MS 244-30, Moffett Field, CA 94035 [email protected] and Laurance R. Doyle SETI Institute, 2035 Landings Drive, Mountain View, CA 94043 [email protected] ABSTRACT NASA’s Kepler Mission promises to detect transiting Earth-sized planets in the habitable zones of solar-like stars. In addition, it will be poised to detect the reflected light component from close-in extrasolar giant planets (CEGPs) similar to 51 Peg b. Here we use the DIARAD/SOHO time series along with models for the reflected light signatures of CEGPs to evaluate Kepler’s ability to detect arXiv:astro-ph/0305473v1 24 May 2003 such planets. We examine the detectability as a function of stellar brightness, stellar rotation period, planetary orbital inclination angle, and planetary orbital period, and then estimate the total number of CEGPs that Kepler will detect over its four year mission. The analysis shows that intrinsic stellar variability of solar-like stars is a major obstacle to detecting the reflected light from CEGPs. Monte Carlo trials are used to estimate the detection threshold required to limit the total number of expected false alarms to no more than one for a survey of 100,000 stellar light curves. Kepler will likely detect 100-760 51 Peg b-like planets by reflected light with orbital periods up to 7 days. Subject headings: planetary systems — techniques: photometry — methods: data analysis –2– 1.
    [Show full text]
  • Long-Term Activity in Photospheres of Low-Mass Stars with Strong Magnetic Fields
    Geomagnetism and Aeronomy, 2020, Vol. 60, No. 7 LONG-TERM ACTIVITY IN PHOTOSPHERES OF LOW-MASS STARS WITH STRONG MAGNETIC FIELDS N. I. Bondar’1*, M. M. Katsova2** Abstract The behavior of the average annual luminosity of K–M dwarfs OU Gem, EQ Vir, V1005 Ori and AU Mic was studied at time intervals of several decades. The main sources of photometric data for 1989–2019 were the Hipparcos, ASAS, KWS databases. An analysis of long-term series showed that the average annual brightness of all stars varies cyclical. The durations of possible cycles for OU Gem, V1005 Ori and AU Mic are 40–42 years, for EQ Vir – 16.6 years, and amplitudes of cycles are of 0.09–0.2m. The selected stars belong to the group of red dwarfs for which the average surface magnetic field hBi exceeds of several kilogauss. We examined the type of the relationship between the parameters of the cycle, its duration and amplitude, for 9 stars with hBi < 4 kG. A tendency to increasing of the amplitude and duration of the cycle when the value of hBi decrease has been noted. It may be suggested that with an increasing of the surface magnetic field, it becomes more uniform and the level of activity changes in this case in less degrees than on stars with strong local fields concentrated in large spots. Keywords stars: activity – stars: cycles – stars: starspots – techniques: photometry 1 Crimean Astrophysical Observatory RAS, Nauchny, Russia 2 Sternberg State Astronomical Institute, Lomonosov Moscow State University, Moscow, Russia *e-mail: [email protected] **e-mail: [email protected] Received: March 07, 2020.
    [Show full text]
  • A Basic Requirement for Studying the Heavens Is Determining Where In
    Abasic requirement for studying the heavens is determining where in the sky things are. To specify sky positions, astronomers have developed several coordinate systems. Each uses a coordinate grid projected on to the celestial sphere, in analogy to the geographic coordinate system used on the surface of the Earth. The coordinate systems differ only in their choice of the fundamental plane, which divides the sky into two equal hemispheres along a great circle (the fundamental plane of the geographic system is the Earth's equator) . Each coordinate system is named for its choice of fundamental plane. The equatorial coordinate system is probably the most widely used celestial coordinate system. It is also the one most closely related to the geographic coordinate system, because they use the same fun­ damental plane and the same poles. The projection of the Earth's equator onto the celestial sphere is called the celestial equator. Similarly, projecting the geographic poles on to the celest ial sphere defines the north and south celestial poles. However, there is an important difference between the equatorial and geographic coordinate systems: the geographic system is fixed to the Earth; it rotates as the Earth does . The equatorial system is fixed to the stars, so it appears to rotate across the sky with the stars, but of course it's really the Earth rotating under the fixed sky. The latitudinal (latitude-like) angle of the equatorial system is called declination (Dec for short) . It measures the angle of an object above or below the celestial equator. The longitud inal angle is called the right ascension (RA for short).
    [Show full text]
  • The Transfiguration in the Theology of Gregory Palamas And
    Duquesne University Duquesne Scholarship Collection Electronic Theses and Dissertations Spring 2015 Deus in se et Deus pro nobis: The rT ansfiguration in the Theology of Gregory Palamas and Its Importance for Catholic Theology Cory Hayes Follow this and additional works at: https://dsc.duq.edu/etd Recommended Citation Hayes, C. (2015). Deus in se et Deus pro nobis: The rT ansfiguration in the Theology of Gregory Palamas and Its Importance for Catholic Theology (Doctoral dissertation, Duquesne University). Retrieved from https://dsc.duq.edu/etd/640 This Immediate Access is brought to you for free and open access by Duquesne Scholarship Collection. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of Duquesne Scholarship Collection. For more information, please contact [email protected]. DEUS IN SE ET DEUS PRO NOBIS: THE TRANSFIGURATION IN THE THEOLOGY OF GREGORY PALAMAS AND ITS IMPORTANCE FOR CATHOLIC THEOLOGY A Dissertation Submitted to the McAnulty Graduate School of Liberal Arts Duquesne University In partial fulfillment of the requirements for the degree of Doctor of Philosophy By Cory J. Hayes May 2015 Copyright by Cory J. Hayes 2015 DEUS IN SE ET DEUS PRO NOBIS: THE TRANSFIGURATION IN THE THEOLOGY OF GREGORY PALAMAS AND ITS IMPORTANCE FOR CATHOLIC THEOLOGY By Cory J. Hayes Approved March 31, 2015 _______________________________ ______________________________ Dr. Bogdan Bucur Dr. Radu Bordeianu Associate Professor of Theology Associate Professor of Theology (Committee Chair) (Committee Member) _______________________________ Dr. Christiaan Kappes Professor of Liturgy and Patristics Saints Cyril and Methodius Byzantine Catholic Seminary (Committee Member) ________________________________ ______________________________ Dr. James Swindal Dr.
    [Show full text]
  • Variable Star Classification and Light Curves Manual
    Variable Star Classification and Light Curves An AAVSO course for the Carolyn Hurless Online Institute for Continuing Education in Astronomy (CHOICE) This is copyrighted material meant only for official enrollees in this online course. Do not share this document with others. Please do not quote from it without prior permission from the AAVSO. Table of Contents Course Description and Requirements for Completion Chapter One- 1. Introduction . What are variable stars? . The first known variable stars 2. Variable Star Names . Constellation names . Greek letters (Bayer letters) . GCVS naming scheme . Other naming conventions . Naming variable star types 3. The Main Types of variability Extrinsic . Eclipsing . Rotating . Microlensing Intrinsic . Pulsating . Eruptive . Cataclysmic . X-Ray 4. The Variability Tree Chapter Two- 1. Rotating Variables . The Sun . BY Dra stars . RS CVn stars . Rotating ellipsoidal variables 2. Eclipsing Variables . EA . EB . EW . EP . Roche Lobes 1 Chapter Three- 1. Pulsating Variables . Classical Cepheids . Type II Cepheids . RV Tau stars . Delta Sct stars . RR Lyr stars . Miras . Semi-regular stars 2. Eruptive Variables . Young Stellar Objects . T Tau stars . FUOrs . EXOrs . UXOrs . UV Cet stars . Gamma Cas stars . S Dor stars . R CrB stars Chapter Four- 1. Cataclysmic Variables . Dwarf Novae . Novae . Recurrent Novae . Magnetic CVs . Symbiotic Variables . Supernovae 2. Other Variables . Gamma-Ray Bursters . Active Galactic Nuclei 2 Course Description and Requirements for Completion This course is an overview of the types of variable stars most commonly observed by AAVSO observers. We discuss the physical processes behind what makes each type variable and how this is demonstrated in their light curves. Variable star names and nomenclature are placed in a historical context to aid in understanding today’s classification scheme.
    [Show full text]
  • The Kinematic Signature of the Galactic Warp in Gaia DR1-I. the Hipparcos Subsample
    Astronomy & Astrophysics manuscript no. WarpGaia c ESO 2021 September 26, 2021 The kinematic signature of the Galactic warp in Gaia DR1 I. The Hipparcos sub-sample E. Poggio1; 2, R. Drimmel2, R. L. Smart2; 3, A. Spagna2, and M. G. Lattanzi2 1 Università di Torino, Dipartimento di Fisica, via P. Giuria 1, 10125 Torino, Italy 2 Osservatorio Astrofisico di Torino, Istituto Nazionale di Astrofisica (INAF), Strada Osservatorio 20, 10025 Pino Torinese, Italy 3 School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK ABSTRACT Context. The mechanism responsible for the warp of our Galaxy, as well as its dynamical nature, continues to remain unknown. With the advent of high precision astrometry, new horizons have been opened for detecting the kinematics associated with the warp and constraining possible warp formation scenarios for the Milky Way. Aims. The aim of this contribution is to establish whether the first Gaia data release (DR1) shows significant evidence of the kinematic signature expected from a long-lived Galactic warp in the kinematics of distant OB stars. As the first paper in a series, we present our approach for analyzing the proper motions and apply it to the sub-sample of Hipparcos stars. Methods. We select a sample of 989 distant spectroscopically-identified OB stars from the New Reduction of Hipparcos (van Leeuwen 2008), of which 758 are also in the first Gaia data release (DR1), covering distances from 0.5 to 3 kpc from the Sun. We develop a model of the spatial distribution and kinematics of the OB stars from which we produce the probability distribution functions of the proper motions, with and without the systematic motions expected from a long-lived warp.
    [Show full text]
  • List of Easy Double Stars for Winter and Spring  = Easy  = Not Too Difficult  = Difficult but Possible
    List of Easy Double Stars for Winter and Spring = easy = not too difficult = difficult but possible 1. Sigma Cassiopeiae (STF 3049). 23 hr 59.0 min +55 deg 45 min This system is tight but very beautiful. Use a high magnification (150x or more). Primary: 5.2, yellow or white Seconary: 7.2 (3.0″), blue 2. Eta Cassiopeiae (Achird, STF 60). 00 hr 49.1 min +57 deg 49 min This is a multiple system with many stars, but I will restrict myself to the brightest one here. Primary: 3.5, yellow. Secondary: 7.4 (13.2″), purple or brown 3. 65 Piscium (STF 61). 00 hr 49.9 min +27 deg 43 min Primary: 6.3, yellow Secondary: 6.3 (4.1″), yellow 4. Psi-1 Piscium (STF 88). 01 hr 05.7 min +21 deg 28 min This double forms a T-shaped asterism with Psi-2, Psi-3 and Chi Piscium. Psi-1 is the uppermost of the four. Primary: 5.3, yellow or white Secondary: 5.5 (29.7), yellow or white 5. Zeta Piscium (STF 100). 01 hr 13.7 min +07 deg 35 min Primary: 5.2, white or yellow Secondary: 6.3, white or lilac (or blue) 6. Gamma Arietis (Mesarthim, STF 180). 01 hr 53.5 min +19 deg 18 min “The Ram’s Eyes” Primary: 4.5, white Secondary: 4.6 (7.5″), white 7. Lambda Arietis (H 5 12). 01 hr 57.9 min +23 deg 36 min Primary: 4.8, white or yellow Secondary: 6.7 (37.1″), silver-white or blue 8.
    [Show full text]
  • Milan Dimitrijevic Avgust.Qxd
    1. M. Platiša, M. Popović, M. Dimitrijević, N. Konjević: 1975, Z. Fur Natur- forsch. 30a, 212 [A 1].* 1. Griem, H. R.: 1975, Stark Broadening, Adv. Atom. Molec. Phys. 11, 331. 2. Platiša, M., Popović, M. V., Konjević, N.: 1975, Stark broadening of O II and O III lines, Astron. Astrophys. 45, 325. 3. Konjević, N., Wiese, W. L.: 1976, Experimental Stark widths and shifts for non-hydrogenic spectral lines of ionized atoms, J. Phys. Chem. Ref. Data 5, 259. 4. Hey, J. D.: 1977, On the Stark broadening of isolated lines of F (II) and Cl (III) by plasmas, JQSRT 18, 649. 5. Hey, J. D.: 1977, Estimates of Stark broadening of some Ar III and Ar IV lines, JQSRT 17, 729. 6. Hey, J. D.: Breger, P.: 1980, Stark broadening of isolated lines emitted by singly - ionized tin, JQSRT 23, 311. 7. Hey, J. D.: Breger, P.: 1981, Stark broadening of isolated ion lines by plas- mas: Application of theory, in Spectral Line Shapes I, ed. B. Wende, W. de Gruyter, 201. 8. Сыркин, М. И.: 1981, Расчеты электронного уширения спектральных линий в теории оптических свойств плазмы, Опт. Спектроск. 51, 778. 9. Wiese, W. L., Konjević, N.: 1982, Regularities and similarities in plasma broadened spectral line widths (Stark widths), JQSRT 28, 185. 10. Konjević, N., Pittman, T. P.: 1986, Stark broadening of spectral lines of ho- mologous, doubly ionized inert gases, JQSRT 35, 473. 11. Konjević, N., Pittman, T. P.: 1987, Stark broadening of spectral lines of ho- mologous, doubly - ionized inert gases, JQSRT 37, 311. 12. Бабин, С.
    [Show full text]