``But I Am Constant As the Northern Star of Whose True-Fixed and Resting Quality There Is No Fellow in the Firmament.'' William
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Plotting Variable Stars on the H-R Diagram Activity
Pulsating Variable Stars and the Hertzsprung-Russell Diagram The Hertzsprung-Russell (H-R) Diagram: The H-R diagram is an important astronomical tool for understanding how stars evolve over time. Stellar evolution can not be studied by observing individual stars as most changes occur over millions and billions of years. Astrophysicists observe numerous stars at various stages in their evolutionary history to determine their changing properties and probable evolutionary tracks across the H-R diagram. The H-R diagram is a scatter graph of stars. When the absolute magnitude (MV) – intrinsic brightness – of stars is plotted against their surface temperature (stellar classification) the stars are not randomly distributed on the graph but are mostly restricted to a few well-defined regions. The stars within the same regions share a common set of characteristics. As the physical characteristics of a star change over its evolutionary history, its position on the H-R diagram The H-R Diagram changes also – so the H-R diagram can also be thought of as a graphical plot of stellar evolution. From the location of a star on the diagram, its luminosity, spectral type, color, temperature, mass, age, chemical composition and evolutionary history are known. Most stars are classified by surface temperature (spectral type) from hottest to coolest as follows: O B A F G K M. These categories are further subdivided into subclasses from hottest (0) to coolest (9). The hottest B stars are B0 and the coolest are B9, followed by spectral type A0. Each major spectral classification is characterized by its own unique spectra. -
Pre-Supernova Evolution of Massive Stars
Pre-Supernova Evolution of Massive Stars ByNINO PANAGIA1;2, AND GIUSEPPE BONO3 1Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA. 2On assignment from the Space Science Department of ESA. 3Osservatorio Astronomico di Roma, Via Frascati 33, Monte Porzio Catone, Italy. We present the preliminary results of a detailed theoretical investigation on the hydrodynamical properties of Red Supergiant (RSG) stars at solar chemical composition and for stellar masses ranging from 10 to 20 M . We find that the main parameter governing their hydrodynamical behaviour is the effective temperature, and indeed when moving from higher to lower effective temperatures the models show an increase in the dynamical perturbations. Also, we find that RSGs are pulsationally unstable for a substantial portion of their lifetimes. These dynamical instabilities play a key role in driving mass loss, thus inducing high mass loss rates (up to −3 −1 almost 10 M yr ) and considerable variations of the mass loss activity over timescales of the order of 104 years. Our results are able to account for the variable mmass loss rates as implied by radio observations of type II supernovae, and we anticipate that comparisons of model predictions with observed circumstellar phenomena around SNII will provide valuable diagnostics about their progenitors and their evolutionary histories. 1. Introduction More than 20 years of radio observations of supernovae (SNe) have provided a wealth of evidence for the presence of substantial amounts of circumstellar material (CSM) surrounding the progenitors of SNe of type II and Ib/c (see Weiler et al., this Conference, and references therein). -
121012-AAS-221 Program-14-ALL, Page 253 @ Preflight
221ST MEETING OF THE AMERICAN ASTRONOMICAL SOCIETY 6-10 January 2013 LONG BEACH, CALIFORNIA Scientific sessions will be held at the: Long Beach Convention Center 300 E. Ocean Blvd. COUNCIL.......................... 2 Long Beach, CA 90802 AAS Paper Sorters EXHIBITORS..................... 4 Aubra Anthony ATTENDEE Alan Boss SERVICES.......................... 9 Blaise Canzian Joanna Corby SCHEDULE.....................12 Rupert Croft Shantanu Desai SATURDAY.....................28 Rick Fienberg Bernhard Fleck SUNDAY..........................30 Erika Grundstrom Nimish P. Hathi MONDAY........................37 Ann Hornschemeier Suzanne H. Jacoby TUESDAY........................98 Bethany Johns Sebastien Lepine WEDNESDAY.............. 158 Katharina Lodders Kevin Marvel THURSDAY.................. 213 Karen Masters Bryan Miller AUTHOR INDEX ........ 245 Nancy Morrison Judit Ries Michael Rutkowski Allyn Smith Joe Tenn Session Numbering Key 100’s Monday 200’s Tuesday 300’s Wednesday 400’s Thursday Sessions are numbered in the Program Book by day and time. Changes after 27 November 2012 are included only in the online program materials. 1 AAS Officers & Councilors Officers Councilors President (2012-2014) (2009-2012) David J. Helfand Quest Univ. Canada Edward F. Guinan Villanova Univ. [email protected] [email protected] PAST President (2012-2013) Patricia Knezek NOAO/WIYN Observatory Debra Elmegreen Vassar College [email protected] [email protected] Robert Mathieu Univ. of Wisconsin Vice President (2009-2015) [email protected] Paula Szkody University of Washington [email protected] (2011-2014) Bruce Balick Univ. of Washington Vice-President (2010-2013) [email protected] Nicholas B. Suntzeff Texas A&M Univ. suntzeff@aas.org Eileen D. Friel Boston Univ. [email protected] Vice President (2011-2014) Edward B. Churchwell Univ. of Wisconsin Angela Speck Univ. of Missouri [email protected] [email protected] Treasurer (2011-2014) (2012-2015) Hervey (Peter) Stockman STScI Nancy S. -
Commission G1 Binary and Multiple Star Systems 1
Transactions IAU, Volume XXXIA Reports on Astronomy 2018-2021 c 2021 International Astronomical Union Maria Teresa Lago, ed. DOI: 00.0000/X000000000000000X COMMISSION G1 BINARY AND MULTIPLE STAR SYSTEMS PRESIDENT Virginia Trimble VICE-PRESIDENT Christopher Adam Tout SECRETARY John Southworth ORGANIZING COMMITTEE Scott William Fleming, Ilya Mandel, Brian D. Mason, Terry D. Oswalt, Alexandre Roman-Lopes TRIENNIAL REPORT 2018{2021 1. Activities of IAU Commission G1 during 2018-2021 by Virginia Trimble (President), as transcribed by David Soderblom (Division G President) It has been a very good three years for binary and multiple systems of stars! If you go to the Astrophysics Data System (which we all know and use more often than we are perhaps prepared to admit) and ask it for any author in the period 2018-02 to 2021-02 and then, sequentially, \binary star," \double star," and \multiple system of stars" there comes back (or did on about 10 March 2020, for the three headings) 9,914 papers with 77,340 citations; 2,496 papers with 14,756 citations, and 3,982 papers with 24,069 citations, respectively. Thus if the three were human beings, they would have h indices of 88, 50, and 57 respectively. There is a small catch: the words do not have to be contiguous in the abstract or keywords, they just both have to be there, so a few of the papers retrieved are not even about astronomy. It is a bit like a very earnest, literal-minded dog, who, asked to bring The Times, returns with three discordant watches. The most-cited binary star paper was B.P. -
Determining Pulsation Period for an RR Lyrae Star
Leah Fabrizio Dr. Mitchell 06/10/2010 Determining Pulsation Period for an RR Lyrae Star As children we used to sing in wonderment of the twinkling stars above and many of us asked, “Why do stars twinkle?” All stars twinkle because their emitted light travels through the Earth’s atmosphere of turbulent gas and clouds that move and shift causing the traversing light to fluctuate. This means that the actual light output of the star is not changing. However there are a number of stars called Variable Stars that actually produce light of varying brightness before it hits the Earth’s atmosphere. There are two categories of variable stars: the intrinsic, where light fluctuation is due from the star physically changing and producing different luminosities, and extrinsic, where the amount of starlight varies due to another star eclipsing or blocking the star’s light from reaching earth (AAVSO 2010). Within the category of intrinsic variable stars are the pulsating variables that have a periodic change in brightness due to the actual size and light production of the star changing; within this group are the RR Lyrae stars (“variable star” 2010). For my research project, I will observe an RR Lyrae and find the period of its luminosity pulsation. The first RR Lyrae star was named after its namesake star (Strobel 2004). It was first found while astronomers were studying the longer period variable stars Cepheids and stood out because of its short period. In comparison to Cepheids, RR Lyraes are smaller and therefore fainter with a shorter period as well as being much older. -
A Refined Search for Pulsations in White Dwarf Companions To
MNRAS 479, 1267–1272 (2018) doi:10.1093/mnras/sty1546 Advance Access publication 2018 June 12 A refined search for pulsations in white dwarf companions to millisecond pulsars Mukremin Kilic,1,2† J. J. Hermes,3‡ A. H. Corsico,´ 4 Alekzander Kosakowski,1 Warren R. Brown,5 John Antoniadis,6 Leila M. Calcaferro,4 A. Gianninas,1 Leandro G. Althaus4 and M. J. Green7 1Department of Physics and Astronomy, University of Oklahoma, 440 W. Brooks St., Norman, OK 73019, USA 2Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK 3Department of Physics and Astronomy, University of North Carolina, Chapel Hill NC 27599, USA 4Facultad de Ciencias Astronomicas´ y Geof´ısicas (UNLP), La Plata, Argentina 5Smithsonian Astrophysical Observatory, 60 Garden St, Cambridge MA 02138, USA 6Dunlap Institute for Astronomy & Astrophysics, University of Toronto, 50 St. George Street, Toronto M5S 3H4, Canada 7Astronomy and Astrophysics Group, Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK Accepted 2018 June 7. Received 2018 May 27; in original form 2018 April 11 ABSTRACT We present optical high-speed photometry of three millisecond pulsars with low-mass (<0.3 M) white dwarf companions, bringing the total number of such systems with follow-up time-series photometry to five. We confirm the detection of pulsations in one system, the white dwarf companion to PSR J1738+0333, and show that the pulsation frequencies and amplitudes are variable over many months. A full asteroseismic analysis for this star is underconstrained, but the mode periods we observe are consistent with expectations for an M = 0.16 − 0.19 M white dwarf, as suggested from spectroscopy. -
Searching for RR Lyrae Stars in M15
Searching for RR Lyrae Stars in M15 ARCC Scholar thesis in partial fulfillment of the requirements of the ARCC Scholar program Khalid Kayal February 1, 2013 Abstract The expansion and contraction of an RR Lyrae star provides a high level of interest to research in astronomy because of the several intrinsic properties that can be studied. We did a systematic search for RR Lyrae stars in the globular cluster M15 using the Catalina Real-time Transient Survey (CRTS). The CRTS searches for rapidly moving Near Earth Objects and stationary optical transients. We created an algorithm to create a hexagonal tiling grid to search the area around a given sky coordinate. We recover light curve plots that are produced by the CRTS and, using the Lafler-Kinman search algorithm, we determine the period, which allows us to identify RR Lyrae stars. We report the results of this search. i Glossary of Abbreviations and Symbols CRTS Catalina Real-time Transient Survey RR A type of variable star M15 Messier 15 RA Right Ascension DEC Declination RF Radio frequency GC Globular cluster H-R Hertzsprung-Russell SDSS Sloan Digital Sky Survey CCD Couple-Charged Device Photcat DB Photometry Catalog Database FAP False Alarm Probability ii Contents 1 Introduction 1 2 Background on RR Lyrae Stars 5 2.1 What are RR Lyraes? . 5 2.2 Types of RR Lyrae Stars . 6 2.3 Stellar Evolution . 8 2.4 Pulsating Mechanism . 9 3 Useful Tools and Surveys 10 3.1 Choosing M15 . 10 3.2 Catalina Real-time Transient Survey . 11 3.3 The Sloan Digital Sky Survey . -
Gaia Data Release 2 Special Issue
A&A 623, A110 (2019) Astronomy https://doi.org/10.1051/0004-6361/201833304 & © ESO 2019 Astrophysics Gaia Data Release 2 Special issue Gaia Data Release 2 Variable stars in the colour-absolute magnitude diagram?,?? Gaia Collaboration, L. Eyer1, L. Rimoldini2, M. Audard1, R. I. Anderson3,1, K. Nienartowicz2, F. Glass1, O. Marchal4, M. Grenon1, N. Mowlavi1, B. Holl1, G. Clementini5, C. Aerts6,7, T. Mazeh8, D. W. Evans9, L. Szabados10, A. G. A. Brown11, A. Vallenari12, T. Prusti13, J. H. J. de Bruijne13, C. Babusiaux4,14, C. A. L. Bailer-Jones15, M. Biermann16, F. Jansen17, C. Jordi18, S. A. Klioner19, U. Lammers20, L. Lindegren21, X. Luri18, F. Mignard22, C. Panem23, D. Pourbaix24,25, S. Randich26, P. Sartoretti4, H. I. Siddiqui27, C. Soubiran28, F. van Leeuwen9, N. A. Walton9, F. Arenou4, U. Bastian16, M. Cropper29, R. Drimmel30, D. Katz4, M. G. Lattanzi30, J. Bakker20, C. Cacciari5, J. Castañeda18, L. Chaoul23, N. Cheek31, F. De Angeli9, C. Fabricius18, R. Guerra20, E. Masana18, R. Messineo32, P. Panuzzo4, J. Portell18, M. Riello9, G. M. Seabroke29, P. Tanga22, F. Thévenin22, G. Gracia-Abril33,16, G. Comoretto27, M. Garcia-Reinaldos20, D. Teyssier27, M. Altmann16,34, R. Andrae15, I. Bellas-Velidis35, K. Benson29, J. Berthier36, R. Blomme37, P. Burgess9, G. Busso9, B. Carry22,36, A. Cellino30, M. Clotet18, O. Creevey22, M. Davidson38, J. De Ridder6, L. Delchambre39, A. Dell’Oro26, C. Ducourant28, J. Fernández-Hernández40, M. Fouesneau15, Y. Frémat37, L. Galluccio22, M. García-Torres41, J. González-Núñez31,42, J. J. González-Vidal18, E. Gosset39,25, L. P. Guy2,43, J.-L. Halbwachs44, N. C. Hambly38, D. -
(NASA/Chandra X-Ray Image) Type Ia Supernova Remnant – Thermonuclear Explosion of a White Dwarf
Stellar Evolution Card Set Description and Links 1. Tycho’s SNR (NASA/Chandra X-ray image) Type Ia supernova remnant – thermonuclear explosion of a white dwarf http://chandra.harvard.edu/photo/2011/tycho2/ 2. Protostar formation (NASA/JPL/Caltech/Spitzer/R. Hurt illustration) A young star/protostar forming within a cloud of gas and dust http://www.spitzer.caltech.edu/images/1852-ssc2007-14d-Planet-Forming-Disk- Around-a-Baby-Star 3. The Crab Nebula (NASA/Chandra X-ray/Hubble optical/Spitzer IR composite image) A type II supernova remnant with a millisecond pulsar stellar core http://chandra.harvard.edu/photo/2009/crab/ 4. Cygnus X-1 (NASA/Chandra/M Weiss illustration) A stellar mass black hole in an X-ray binary system with a main sequence companion star http://chandra.harvard.edu/photo/2011/cygx1/ 5. White dwarf with red giant companion star (ESO/M. Kornmesser illustration/video) A white dwarf accreting material from a red giant companion could result in a Type Ia supernova http://www.eso.org/public/videos/eso0943b/ 6. Eight Burst Nebula (NASA/Hubble optical image) A planetary nebula with a white dwarf and companion star binary system in its center http://apod.nasa.gov/apod/ap150607.html 7. The Carina Nebula star-formation complex (NASA/Hubble optical image) A massive and active star formation region with newly forming protostars and stars http://www.spacetelescope.org/images/heic0707b/ 8. NGC 6826 (Chandra X-ray/Hubble optical composite image) A planetary nebula with a white dwarf stellar core in its center http://chandra.harvard.edu/photo/2012/pne/ 9. -
Cepheid Variable Stars Cepheid Variable Stars As Distance Indicators
Cepheid Variable Stars Cepheid variable stars as distance indicators. Certain stars that have used up their main supply of hydrogen fuel are unstable and pulsate. RR Lyrae variables have periods of about a day. Their brightness doubles from dimest to brightest. Typical light curve for a Cepheid variable star. Cepheid variables have longer periods, from one day up to about 50 days. Their brightness also doubles from dimest to brightest. From the shape of the ``light curve'' of a Cepheid variable star, one can tell that it is a Cepheid variable. The period is simple to measure, as is the apparent brightness at maximum brightness. Cepheids as distance indicators Cepheids are important beyond their intrinsic interest as pulsating stars. Astronomomers have found that their is a relation between the period of a Cepheid and its luminosity. http://zebu.uoregon.edu/~soper/MilkyWay/cepheid.html (1 of 3) [5/25/1999 10:34:08 AM] Cepheid Variable Stars This enables astronomers to determine distances: ● Find the period. ● This gives the luminosity. ● Measure the apparent brightness. ● Determine the distance from the luminosity and brightness. The same applies to RR Lyrae variable stars. Once you know that a star is an RR Lyrae variable (eg. from the shape of its light curve), then you know its luminosity. Where did this period-luminosity relation come from? ● American astronomer Henrietta Leavitt looked at many Cepheid variables in the Small Magellanic Cloud (a satellite galaxy to ours.) ● She found the period luminosity relation (reported in 1912). ● One needs a distance measurement from some other method for at least one Cepheid. -
A Comprehensive Study of Cepheid Variables in the Andromeda Galaxy Period Distribution, Blending, and Distance Determination
A&A 473, 847–855 (2007) Astronomy DOI: 10.1051/0004-6361:20077960 & c ESO 2007 Astrophysics A comprehensive study of Cepheid variables in the Andromeda galaxy Period distribution, blending, and distance determination F. Vilardell1,C.Jordi1,3, and I. Ribas2,3 1 Departament d’Astronomia i Meteorologia, Universitat de Barcelona, c/ Martí i Franquès, 1, 08028 Barcelona, Spain e-mail: [francesc.vilardell;carme.jordi]@am.ub.es 2 Institut de Ciències de l’Espai-CSIC, Campus UAB, Facultat de Ciències, Torre C5-parell-2a, 08193 Bellaterra, Spain e-mail: [email protected] 3 Institut d’Estudis Espacials de Catalunya (IEEC), Edif. Nexus, c/ Gran Capità, 2-4, 08034 Barcelona, Spain Received 28 May 2007 / Accepted 18 July 2007 ABSTRACT Extragalactic Cepheids are the basic rungs of the cosmic distance scale. They are excellent standard candles, although their lumi- nosities and corresponding distance estimates can be affected by the particular properties of the host galaxy. Therefore, the accurate analysis of the Cepheid population in other galaxies, and notably in the Andromeda galaxy (M 31), is crucial to obtaining reliable distance determinations. We obtained accurate photometry (in B and V passbands) of 416 Cepheids in M 31 over a five year campaign within a survey aimed at the detection of eclipsing binaries. The resulting Cepheid sample is the most complete in M 31 and has almost the same period distribution as the David Dunlap Observatory sample in the Milky Way. The large number of epochs (∼250 per filter) has permitted the characterisation of the pulsation modes of 356 Cepheids, with 281 of them pulsating in the fundamental mode and 75 in the first overtone. -