Cepheid Variable Stars
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Commission 27 of the Iau Information Bulletin
COMMISSION 27 OF THE I.A.U. INFORMATION BULLETIN ON VARIABLE STARS Nos. 2401 - 2500 1983 September - 1984 March EDITORS: B. SZEIDL AND L. SZABADOS, KONKOLY OBSERVATORY 1525 BUDAPEST, Box 67, HUNGARY HU ISSN 0374-0676 CONTENTS 2401 A POSSIBLE CATACLYSMIC VARIABLE IN CANCER Masaaki Huruhata 20 September 1983 2402 A NEW RR-TYPE VARIABLE IN LEO Masaaki Huruhata 20 September 1983 2403 ON THE DELTA SCUTI STAR BD +43d1894 A. Yamasaki, A. Okazaki, M. Kitamura 23 September 1983 2404 IQ Vel: IMPROVED LIGHT-CURVE PARAMETERS L. Kohoutek 26 September 1983 2405 FLARE ACTIVITY OF EPSILON AURIGAE? I.-S. Nha, S.J. Lee 28 September 1983 2406 PHOTOELECTRIC OBSERVATIONS OF 20 CVn Y.W. Chun, Y.S. Lee, I.-S. Nha 30 September 1983 2407 MINIMUM TIMES OF THE ECLIPSING VARIABLES AH Cep AND IU Aur Pavel Mayer, J. Tremko 4 October 1983 2408 PHOTOELECTRIC OBSERVATIONS OF THE FLARE STAR EV Lac IN 1980 G. Asteriadis, S. Avgoloupis, L.N. Mavridis, P. Varvoglis 6 October 1983 2409 HD 37824: A NEW VARIABLE STAR Douglas S. Hall, G.W. Henry, H. Louth, T.R. Renner 10 October 1983 2410 ON THE PERIOD OF BW VULPECULAE E. Szuszkiewicz, S. Ratajczyk 12 October 1983 2411 THE UNIQUE DOUBLE-MODE CEPHEID CO Aur E. Antonello, L. Mantegazza 14 October 1983 2412 FLARE STARS IN TAURUS A.S. Hojaev 14 October 1983 2413 BVRI PHOTOMETRY OF THE ECLIPSING BINARY QX Cas Thomas J. Moffett, T.G. Barnes, III 17 October 1983 2414 THE ABSOLUTE MAGNITUDE OF AZ CANCRI William P. Bidelman, D. Hoffleit 17 October 1983 2415 NEW DATA ABOUT THE APSIDAL MOTION IN THE SYSTEM OF RU MONOCEROTIS D.Ya. -
White Dwarfs
Chandra X-Ray Observatory X-Ray Astronomy Field Guide White Dwarfs White dwarfs are among the dimmest stars in the universe. Even so, they have commanded the attention of astronomers ever since the first white dwarf was observed by optical telescopes in the middle of the 19th century. One reason for this interest is that white dwarfs represent an intriguing state of matter; another reason is that most stars, including our sun, will become white dwarfs when they reach their final, burnt-out collapsed state. A star experiences an energy crisis and its core collapses when the star's basic, non-renewable energy source - hydrogen - is used up. A shell of hydrogen on the edge of the collapsed core will be compressed and heated. The nuclear fusion of the hydrogen in the shell will produce a new surge of power that will cause the outer layers of the star to expand until it has a diameter a hundred times its present value. This is called the "red giant" phase of a star's existence. A hundred million years after the red giant phase all of the star's available energy resources will be used up. The exhausted red giant will puff off its outer layer leaving behind a hot core. This hot core is called a Wolf-Rayet type star after the astronomers who first identified these objects. This star has a surface temperature of about 50,000 degrees Celsius and is A composite furiously boiling off its outer layers in a "fast" wind traveling 6 million image of the kilometers per hour. -
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. -
JOHN R. THORSTENSEN Address
CURRICULUM VITAE: JOHN R. THORSTENSEN Address: Department of Physics and Astronomy Dartmouth College 6127 Wilder Laboratory Hanover, NH 03755-3528; (603)-646-2869 [email protected] Undergraduate Studies: Haverford College, B. A. 1974 Astronomy and Physics double major, High Honors in both. Graduate Studies: Ph. D., 1980, University of California, Berkeley Astronomy Department Dissertation : \Optical Studies of Faint Blue X-ray Stars" Graduate Advisor: Professor C. Stuart Bowyer Employment History: Department of Physics and Astronomy, Dartmouth College: { Professor, July 1991 { present { Associate Professor, July 1986 { July 1991 { Assistant Professor, September 1980 { June 1986 Research Assistant, Space Sciences Lab., U.C. Berkeley, 1975 { 1980. Summer Student, National Radio Astronomy Observatory, 1974. Summer Student, Bartol Research Foundation, 1973. Consultant, IBM Corporation, 1973. (STARMAP program). Honors and Awards: Phi Beta Kappa, 1974. National Science Foundation Graduate Fellow, 1974 { 1977. Dorothea Klumpke Roberts Award of the Berkeley Astronomy Dept., 1978. Professional Societies: American Astronomical Society Astronomical Society of the Pacific International Astronomical Union Lifetime Publication List * \Can Collapsed Stars Close the Universe?" Thorstensen, J. R., and Partridge, R. B. 1975, Ap. J., 200, 527. \Optical Identification of Nova Scuti 1975." Raff, M. I., and Thorstensen, J. 1975, P. A. S. P., 87, 593. \Photometry of Slow X-ray Pulsars II: The 13.9 Minute Period of X Persei." Margon, B., Thorstensen, J., Bowyer, S., Mason, K. O., White, N. E., Sanford, P. W., Parkes, G., Stone, R. P. S., and Bailey, J. 1977, Ap. J., 218, 504. \A Spectrophotometric Survey of the A 0535+26 Field." Margon, B., Thorstensen, J., Nelson, J., Chanan, G., and Bowyer, S. -
Luminous Blue Variables
Review Luminous Blue Variables Kerstin Weis 1* and Dominik J. Bomans 1,2,3 1 Astronomical Institute, Faculty for Physics and Astronomy, Ruhr University Bochum, 44801 Bochum, Germany 2 Department Plasmas with Complex Interactions, Ruhr University Bochum, 44801 Bochum, Germany 3 Ruhr Astroparticle and Plasma Physics (RAPP) Center, 44801 Bochum, Germany Received: 29 October 2019; Accepted: 18 February 2020; Published: 29 February 2020 Abstract: Luminous Blue Variables are massive evolved stars, here we introduce this outstanding class of objects. Described are the specific characteristics, the evolutionary state and what they are connected to other phases and types of massive stars. Our current knowledge of LBVs is limited by the fact that in comparison to other stellar classes and phases only a few “true” LBVs are known. This results from the lack of a unique, fast and always reliable identification scheme for LBVs. It literally takes time to get a true classification of a LBV. In addition the short duration of the LBV phase makes it even harder to catch and identify a star as LBV. We summarize here what is known so far, give an overview of the LBV population and the list of LBV host galaxies. LBV are clearly an important and still not fully understood phase in the live of (very) massive stars, especially due to the large and time variable mass loss during the LBV phase. We like to emphasize again the problem how to clearly identify LBV and that there are more than just one type of LBVs: The giant eruption LBVs or h Car analogs and the S Dor cycle LBVs. -
Stars IV Stellar Evolution Attendance Quiz
Stars IV Stellar Evolution Attendance Quiz Are you here today? Here! (a) yes (b) no (c) my views are evolving on the subject Today’s Topics Stellar Evolution • An alien visits Earth for a day • A star’s mass controls its fate • Low-mass stellar evolution (M < 2 M) • Intermediate and high-mass stellar evolution (2 M < M < 8 M; M > 8 M) • Novae, Type I Supernovae, Type II Supernovae An Alien Visits for a Day • Suppose an alien visited the Earth for a day • What would it make of humans? • It might think that there were 4 separate species • A small creature that makes a lot of noise and leaks liquids • A somewhat larger, very energetic creature • A large, slow-witted creature • A smaller, wrinkled creature • Or, it might decide that there is one species and that these different creatures form an evolutionary sequence (baby, child, adult, old person) Stellar Evolution • Astronomers study stars in much the same way • Stars come in many varieties, and change over times much longer than a human lifetime (with some spectacular exceptions!) • How do we know they evolve? • We study stellar properties, and use our knowledge of physics to construct models and draw conclusions about stars that lead to an evolutionary sequence • As with stellar structure, the mass of a star determines its evolution and eventual fate A Star’s Mass Determines its Fate • How does mass control a star’s evolution and fate? • A main sequence star with higher mass has • Higher central pressure • Higher fusion rate • Higher luminosity • Shorter main sequence lifetime • Larger -
Supernovae Sparked by Dark Matter in White Dwarfs
Supernovae Sparked By Dark Matter in White Dwarfs Javier F. Acevedog and Joseph Bramanteg;y gThe Arthur B. McDonald Canadian Astroparticle Physics Research Institute, Department of Physics, Engineering Physics, and Astronomy, Queen's University, Kingston, Ontario, K7L 2S8, Canada yPerimeter Institute for Theoretical Physics, Waterloo, Ontario, N2L 2Y5, Canada November 27, 2019 Abstract It was recently demonstrated that asymmetric dark matter can ignite supernovae by collecting and collapsing inside lone sub-Chandrasekhar mass white dwarfs, and that this may be the cause of Type Ia supernovae. A ball of asymmetric dark matter accumulated inside a white dwarf and collapsing under its own weight, sheds enough gravitational potential energy through scattering with nuclei, to spark the fusion reactions that precede a Type Ia supernova explosion. In this article we elaborate on this mechanism and use it to place new bounds on interactions between nucleons 6 16 and asymmetric dark matter for masses mX = 10 − 10 GeV. Interestingly, we find that for dark matter more massive than 1011 GeV, Type Ia supernova ignition can proceed through the Hawking evaporation of a small black hole formed by the collapsed dark matter. We also identify how a cold white dwarf's Coulomb crystal structure substantially suppresses dark matter-nuclear scattering at low momentum transfers, which is crucial for calculating the time it takes dark matter to form a black hole. Higgs and vector portal dark matter models that ignite Type Ia supernovae are explored. arXiv:1904.11993v3 [hep-ph] 26 Nov 2019 Contents 1 Introduction 2 2 Dark matter capture, thermalization and collapse in white dwarfs 4 2.1 Dark matter capture . -
The Impact of the Astro2010 Recommendations on Variable Star Science
The Impact of the Astro2010 Recommendations on Variable Star Science Corresponding Authors Lucianne M. Walkowicz Department of Astronomy, University of California Berkeley [email protected] phone: (510) 642–6931 Andrew C. Becker Department of Astronomy, University of Washington [email protected] phone: (206) 685–0542 Authors Scott F. Anderson, Department of Astronomy, University of Washington Joshua S. Bloom, Department of Astronomy, University of California Berkeley Leonid Georgiev, Universidad Autonoma de Mexico Josh Grindlay, Harvard–Smithsonian Center for Astrophysics Steve Howell, National Optical Astronomy Observatory Knox Long, Space Telescope Science Institute Anjum Mukadam, Department of Astronomy, University of Washington Andrej Prsa,ˇ Villanova University Joshua Pepper, Villanova University Arne Rau, California Institute of Technology Branimir Sesar, Department of Astronomy, University of Washington Nicole Silvestri, Department of Astronomy, University of Washington Nathan Smith, Department of Astronomy, University of California Berkeley Keivan Stassun, Vanderbilt University Paula Szkody, Department of Astronomy, University of Washington Science Frontier Panels: Stars and Stellar Evolution (SSE) February 16, 2009 Abstract The next decade of survey astronomy has the potential to transform our knowledge of variable stars. Stellar variability underpins our knowledge of the cosmological distance ladder, and provides direct tests of stellar formation and evolution theory. Variable stars can also be used to probe the fundamental physics of gravity and degenerate material in ways that are otherwise impossible in the laboratory. The computational and engineering advances of the past decade have made large–scale, time–domain surveys an immediate reality. Some surveys proposed for the next decade promise to gather more data than in the prior cumulative history of astronomy. -
Galaxies – AS 3011
Galaxies – AS 3011 Simon Driver [email protected] ... room 308 This is a Junior Honours 18-lecture course Lectures 11am Wednesday & Friday Recommended book: The Structure and Evolution of Galaxies by Steven Phillipps Galaxies – AS 3011 1 Aims • To understand: – What is a galaxy – The different kinds of galaxy – The optical properties of galaxies – The hidden properties of galaxies such as dark matter, presence of black holes, etc. – Galaxy formation concepts and large scale structure • Appreciate: – Why galaxies are interesting, as building blocks of the Universe… and how simple calculations can be used to better understand these systems. Galaxies – AS 3011 2 1 from 1st year course: • AS 1001 covered the basics of : – distances, masses, types etc. of galaxies – spectra and hence dynamics – exotic things in galaxies: dark matter and black holes – galaxies on a cosmological scale – the Big Bang • in AS 3011 we will study dynamics in more depth, look at other non-stellar components of galaxies, and introduce high-redshift galaxies and the large-scale structure of the Universe Galaxies – AS 3011 3 Outline of lectures 1) galaxies as external objects 13) large-scale structure 2) types of galaxy 14) luminosity of the Universe 3) our Galaxy (components) 15) primordial galaxies 4) stellar populations 16) active galaxies 5) orbits of stars 17) anomalies & enigmas 6) stellar distribution – ellipticals 18) revision & exam advice 7) stellar distribution – spirals 8) dynamics of ellipticals plus 3-4 tutorials 9) dynamics of spirals (questions set after -
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). -
Chapter 16 the Sun and Stars
Chapter 16 The Sun and Stars Stargazing is an awe-inspiring way to enjoy the night sky, but humans can learn only so much about stars from our position on Earth. The Hubble Space Telescope is a school-bus-size telescope that orbits Earth every 97 minutes at an altitude of 353 miles and a speed of about 17,500 miles per hour. The Hubble Space Telescope (HST) transmits images and data from space to computers on Earth. In fact, HST sends enough data back to Earth each week to fill 3,600 feet of books on a shelf. Scientists store the data on special disks. In January 2006, HST captured images of the Orion Nebula, a huge area where stars are being formed. HST’s detailed images revealed over 3,000 stars that were never seen before. Information from the Hubble will help scientists understand more about how stars form. In this chapter, you will learn all about the star of our solar system, the sun, and about the characteristics of other stars. 1. Why do stars shine? 2. What kinds of stars are there? 3. How are stars formed, and do any other stars have planets? 16.1 The Sun and the Stars What are stars? Where did they come from? How long do they last? During most of the star - an enormous hot ball of gas day, we see only one star, the sun, which is 150 million kilometers away. On a clear held together by gravity which night, about 6,000 stars can be seen without a telescope. -
Fy10 Budget by Program
AURA/NOAO FISCAL YEAR ANNUAL REPORT FY 2010 Revised Submitted to the National Science Foundation March 16, 2011 This image, aimed toward the southern celestial pole atop the CTIO Blanco 4-m telescope, shows the Large and Small Magellanic Clouds, the Milky Way (Carinae Region) and the Coal Sack (dark area, close to the Southern Crux). The 33 “written” on the Schmidt Telescope dome using a green laser pointer during the two-minute exposure commemorates the rescue effort of 33 miners trapped for 69 days almost 700 m underground in the San Jose mine in northern Chile. The image was taken while the rescue was in progress on 13 October 2010, at 3:30 am Chilean Daylight Saving time. Image Credit: Arturo Gomez/CTIO/NOAO/AURA/NSF National Optical Astronomy Observatory Fiscal Year Annual Report for FY 2010 Revised (October 1, 2009 – September 30, 2010) Submitted to the National Science Foundation Pursuant to Cooperative Support Agreement No. AST-0950945 March 16, 2011 Table of Contents MISSION SYNOPSIS ............................................................................................................ IV 1 EXECUTIVE SUMMARY ................................................................................................ 1 2 NOAO ACCOMPLISHMENTS ....................................................................................... 2 2.1 Achievements ..................................................................................................... 2 2.2 Status of Vision and Goals ................................................................................