Summary of Eighth Meeting on Hot Subdwarfs and Related Objects
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Hypervelocity Stars Ejected from the Galactic Center
Hypervelocity Stars Ejected from the Galactic Center The Milky Way Halo Conference May 31, 2007 Warren R. Brown Smithsonian Astrophysical Observatory Collaborators: Margaret Geller, Scott Kenyon, Michael Kurtz Hypervelocity stars (HVSs) are stars traveling with such extreme speeds that they are no longer bound to the Galaxy. Hypervelocity stars are interesting because they must be ejected by a massive black hole. As a result, hypervelocity stars give us tools to understand the history stellar interactions with the massive black hole and environment of stars around it. 1 The Milky Way Kaufmann If this is a picture of the Milky Way, the hypervelocity stars we are finding are deep in the halo, at distances of 50 – 100 kpc. The hypervelocity stars we are finding are also B-type stars. B-type stars are stars that are more massive and much more luminous than the Sun. Because B stars burn their fuel very rapidly, they have relatively short lifetimes of order 100 million years. In 1947, Humanson and Zwicky first reported B-type stars at high Galactic latitudes. Because B stars are born in the disk and live only a short time, you wouldn’t expect to find B stars very deep in the halo. Spectroscopic surveys show that the high- latitude B stars are a mix of evolved (horizontal branch) stars that belong to the halo and some main sequence, so-called “run-away B stars.” These run-away B stars all have travel times constant with a disk origin. Run-away stars are explained by two mechanisms: ejections from stellar binary encounters in young star clusters, or when a former binary companion goes supernova. -
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A&A 601, A29 (2017) Astronomy DOI: 10.1051/0004-6361/201629685 & c ESO 2017 Astrophysics Delay-time distribution of core-collapse supernovae with late events resulting from binary interaction E. Zapartas1, S. E. de Mink1, R. G. Izzard2, S.-C. Yoon3, C. Badenes4, Y. Götberg1, A. de Koter1; 5, C. J. Neijssel1, M. Renzo1, A. Schootemeijer6, and T. S. Shrotriya6 1 Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands e-mail: [E.Zapartas;S.E.deMink]@uva.nl 2 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK 3 Astronomy Program, Department of Physics and Astronomy, Seoul National University, 151–747 Seoul, Korea 4 Department of Physics and Astronomy & Pittsburgh Particle Physics, Astrophysics, and Cosmology Center (PITT-PACC), University of Pittsburgh, Pittsburgh, PA 15260, USA 5 Institute of Astronomy, KU Leuven, Celestijnenlaan 200 D, 3001 Leuven, Belgium 6 Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany Received 11 September 2016 / Accepted 1 January 2017 ABSTRACT Most massive stars, the progenitors of core-collapse supernovae, are in close binary systems and may interact with their companion through mass transfer or merging. We undertake a population synthesis study to compute the delay-time distribution of core-collapse supernovae, that is, the supernova rate versus time following a starburst, taking into account binary interactions. We test the systematic robustness of our results by running various simulations to account for the uncertainties in our standard assumptions. We find that +9 a significant fraction, 15−8%, of core-collapse supernovae are “late”, that is, they occur 50–200 Myr after birth, when all massive single stars have already exploded. -
A Stripped Helium Star in the Potential Black Hole Binary LB-1 A
A&A 633, L5 (2020) Astronomy https://doi.org/10.1051/0004-6361/201937343 & c ESO 2020 Astrophysics LETTER TO THE EDITOR A stripped helium star in the potential black hole binary LB-1 A. Irrgang1, S. Geier2, S. Kreuzer1, I. Pelisoli2, and U. Heber1 1 Dr. Karl Remeis-Observatory & ECAP, Astronomical Institute, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Sternwartstr. 7, 96049 Bamberg, Germany e-mail: [email protected] 2 Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam, Germany Received 18 December 2019 / Accepted 1 January 2020 ABSTRACT +11 Context. The recently claimed discovery of a massive (MBH = 68−13 M ) black hole in the Galactic solar neighborhood has led to controversial discussions because it severely challenges our current view of stellar evolution. Aims. A crucial aspect for the determination of the mass of the unseen black hole is the precise nature of its visible companion, the B-type star LS V+22 25. Because stars of different mass can exhibit B-type spectra during the course of their evolution, it is essential to obtain a comprehensive picture of the star to unravel its nature and, thus, its mass. Methods. To this end, we study the spectral energy distribution of LS V+22 25 and perform a quantitative spectroscopic analysis that includes the determination of chemical abundances for He, C, N, O, Ne, Mg, Al, Si, S, Ar, and Fe. Results. Our analysis clearly shows that LS V+22 25 is not an ordinary main sequence B-type star. The derived abundance pattern exhibits heavy imprints of the CNO bi-cycle of hydrogen burning, that is, He and N are strongly enriched at the expense of C and O. -
XMM-Newton Observations of the Galactic Globular Clusters NGC 2808 and NGC 4372
A&A 480, 397–407 (2008) Astronomy DOI: 10.1051/0004-6361:20078327 & c ESO 2008 Astrophysics XMM-Newton observations of the Galactic globular clusters NGC 2808 and NGC 4372 M. Servillat, N. A. Webb, and D. Barret CESR, Université Paul Sabatier, CNRS, 9 avenue du Colonel Roche, 31400 Toulouse, France e-mail: [email protected] Received 20 July 2007 / Accepted 28 November 2007 ABSTRACT Aims. Galactic globular clusters harbour binary systems that are detected as faint X-ray sources. These close binaries are thought to play an important role in the stability of the clusters by liberating energy and delaying the inevitable core collapse of globular clusters. The inventory of close binaries and their identification is therefore essential. Methods. We present XMM-Newton observations of two Galactic globular clusters: NGC 2808 and NGC 4372. We use X-ray spectral and variability analysis combined with ultra-violet observations made with the XMM-Newton optical monitor and published data from the Hubble Space Telescope to identify sources associated with the clusters. We compare the results of our observations with estimates from population synthesis models. Results. Five sources out of 96 are likely to be related to NGC 2808. Nine sources are found in the field of view of NGC 4372, none being located inside its half-mass radius. We find one quiescent neutron star low mass X-ray binary candidate in the core of NGC 2808, and propose that the majority of the central sources in NGC 2808 are cataclysmic variables. An estimation leads to 20±10 cataclysmic variables with luminosity above 4.25 × 1031 erg s−1. -
Hydrogen-Deficient Stars
Hydrogen-Deficient Stars ASP Conference Series, Vol. 391, c 2008 K. Werner and T. Rauch, eds. Hydrogen-Deficient Stars: An Introduction C. Simon Jeffery Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland, UK Abstract. We describe the discovery, classification and statistics of hydrogen- deficient stars in the Galaxy and beyond. The stars are divided into (i) massive / young star evolution, (ii) low-mass supergiants, (iii) hot subdwarfs, (iv) cen- tral stars of planetary nebulae, and (v) white dwarfs. We introduce some of the challenges presented by these stars for understanding stellar structure and evolution. 1. Beginning Our science begins with a young woman from Dundee in Scotland. The brilliant Williamina Fleming had found herself in the employment of Pickering at the Harvard Observatory where she noted that “the spectrum of υ Sgr is remarkable since the hydrogen lines are very faint and of the same intensity as the additional dark lines” (Fleming 1891). Other stars, well-known at the time, later turned out also to have an unusual hydrogen signature; the spectacular light variations of R CrB had been known for a century (Pigott 1797), while Wolf & Rayet (1867) had discovered their emission-line stars some forty years prior. It was fifteen years after Fleming’s discovery that Ludendorff (1906) observed Hγ to be completely absent from the spectrum of R CrB, while arguments about the hydrogen content of Wolf-Rayet stars continued late into the 20th century. Although these early observations pointed to something unusual in the spec- tra of a variety of stars, there was reluctance to accept (or even suggest) that hydrogen might be deficient. -
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). -
High-Precision Asteroseismology of Dense Stellar Fields
Experimental Astronomy https://doi.org/10.1007/s10686-021-09711-1 ORIGINAL ARTICLE HAYDN High-precision AsteroseismologY of DeNse stellar fields Andrea Miglio1,2,3 · Leo´ Girardi4 · Frank Grundahl5 · Benoit Mosser6 · Nate Bastian7 · Angela Bragaglia3 · Karsten Brogaard5,8 · Gael¨ Buldgen9 · William Chantereau7 · William Chaplin1 · Cristina Chiappini10 · Marc-Antoine Dupret11 · Patrick Eggenberger9 · Mark Gieles12,13 · Robert Izzard14 · Daisuke Kawata15 · Christoffer Karoff5 · Nadege` Lagarde16 · Ted Mackereth1,17,18,19 · Demetrio Magrin4 · Georges Meynet9 · Eric Michel20 · Josefina Montalban´ 1 · Valerio Nascimbeni4 · Arlette Noels11 · Giampaolo Piotto21 · Roberto Ragazzoni4 · Igor Soszynski´ 22 · Eline Tolstoy23 · Silvia Toonen1,24 · Amaury Triaud1 · Fiorenzo Vincenzo1,25 Received: 29 July 2020 / Accepted: 9 February 2021 / © The Author(s) 2021 Abstract In the last decade, the Kepler and CoRoT space-photometry missions have demon- strated the potential of asteroseismology as a novel, versatile and powerful tool to perform exquisite tests of stellar physics, and to enable precise and accurate char- acterisations of stellar properties, with impact on both exoplanetary and Galactic astrophysics. Based on our improved understanding of the strengths and limitations of such a tool, we argue for a new small/medium space mission dedicated to gath- ering high-precision, high-cadence, long photometric series in dense stellar fields. Such a mission will lead to breakthroughs in stellar astrophysics, especially in the metal poor regime, will elucidate the evolution and formation of open and globular clusters, and aid our understanding of the assembly history and chemodynamics of the Milky Way’s bulge and a few nearby dwarf galaxies. Keywords Stars: low-mass · Globular clusters · Galaxy: bulge · Galaxies: dwarf · Asteroseismology A list of people who have expressed interest for HAYDN is available here: https://www.asterochronometry.eu/haydn/people.html Andrea Miglio [email protected] Extended author information available on the last page of the article. -
White Dwarf and Hot Subdwarf Binaries As Possible Progenitors of Type I A
White dwarf and hot sub dwarf binaries as p ossible progenitors of type I a Sup ernovae Christian Karl July White dwarf and hot sub dwarf binaries as p ossible progenitors of type I a Sup ernovae Den Naturwissenschaftlichen Fakultaten der FriedrichAlexanderUniversitatErlangenN urnberg zur Erlangung des Doktorgrades vorgelegt von Christian Karl aus Bamberg Als Dissertation genehmigt von den Naturwissenschaftlichen Fakultaten der UniversitatErlangenN urnberg Tag der m undlichen Pr ufung Aug Vositzender der Promotionskommission Prof Dr L Dahlenburg Erstb erichterstatter Prof Dr U Heb er Zweitberichterstatter Prof Dr K Werner Contents The SPY pro ject Selection of DB white dwarfs Color criteria Absorption line criteria Summary of the DB selection The UV Visual Echelle Sp ectrograph Instrumental setup UVES data reduction ESO pip elin e vs semiautomated pip eline Derivation of system parameters Denition of samples Radial velocity curves Followup observations Radial velocity measurements Power sp ectra and RV curves Gravitational redshift Quantitative sp ectroscopic analysis Stellar parameters of singleline d systems -
ESO Annual Report 2004 ESO Annual Report 2004 Presented to the Council by the Director General Dr
ESO Annual Report 2004 ESO Annual Report 2004 presented to the Council by the Director General Dr. Catherine Cesarsky View of La Silla from the 3.6-m telescope. ESO is the foremost intergovernmental European Science and Technology organi- sation in the field of ground-based as- trophysics. It is supported by eleven coun- tries: Belgium, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Sweden, Switzerland and the United Kingdom. Created in 1962, ESO provides state-of- the-art research facilities to European astronomers and astrophysicists. In pur- suit of this task, ESO’s activities cover a wide spectrum including the design and construction of world-class ground-based observational facilities for the member- state scientists, large telescope projects, design of innovative scientific instruments, developing new and advanced techno- logies, furthering European co-operation and carrying out European educational programmes. ESO operates at three sites in the Ataca- ma desert region of Chile. The first site The VLT is a most unusual telescope, is at La Silla, a mountain 600 km north of based on the latest technology. It is not Santiago de Chile, at 2 400 m altitude. just one, but an array of 4 telescopes, It is equipped with several optical tele- each with a main mirror of 8.2-m diame- scopes with mirror diameters of up to ter. With one such telescope, images 3.6-metres. The 3.5-m New Technology of celestial objects as faint as magnitude Telescope (NTT) was the first in the 30 have been obtained in a one-hour ex- world to have a computer-controlled main posure. -
The Story of AA Doradus As Revealed by Its Cool Companion
A&A 586, A146 (2016) Astronomy DOI: 10.1051/0004-6361/201526552 & c ESO 2016 Astrophysics Looking on the bright side: The story of AA Doradus as revealed by its cool companion M. Vuckoviˇ c´1,5, R. H. Østensen2, P. Németh2,3, S. Bloemen2,4, and P. I. Pápics2 1 Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Gran Bretaña 1111, Playa Ancha, 2360102 Valparaíso, Chile e-mail: [email protected] 2 Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium 3 Dr. Karl-Remeis-Observatory & ECAP, Astronomical Institute, F.-A.-U. Erlangen-Nürnberg, 96049 Bamberg, Germany 4 Department of Astrophysics, IMAPP, Radboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands 5 Astronomical Observatory of Belgrade, Volgina 7, 11060 Belgrade, Serbia Received 18 May 2015 / Accepted 1 October 2015 ABSTRACT The effects of irradiation on the secondary stars of close binary systems are crucial for reliably determining the system parameters and for understanding the close binary evolution. They affect the stellar structure of the irradiated star and are reflected in the appearance of characteristic features in the spectroscopic and photometric data of these systems. We aim to study the light that originates from the irradiated side of the low-mass component of a close binary eclipsing system, which comprises a hot subdwarf primary and a low mass companion, to precisely interpret their high precision photometric and spectroscopic data, and accurately determine their system and surface parameters. We reanalyse the archival high-resolution time-resolved VLT/UVES spectra of AA Dor system, where irradiation features have already been detected. -
Arxiv:2006.10868V2 [Astro-Ph.SR] 9 Apr 2021 Spain and Institut D’Estudis Espacials De Catalunya (IEEC), C/Gran Capit`A2-4, E-08034 2 Serenelli, Weiss, Aerts Et Al
Noname manuscript No. (will be inserted by the editor) Weighing stars from birth to death: mass determination methods across the HRD Aldo Serenelli · Achim Weiss · Conny Aerts · George C. Angelou · David Baroch · Nate Bastian · Paul G. Beck · Maria Bergemann · Joachim M. Bestenlehner · Ian Czekala · Nancy Elias-Rosa · Ana Escorza · Vincent Van Eylen · Diane K. Feuillet · Davide Gandolfi · Mark Gieles · L´eoGirardi · Yveline Lebreton · Nicolas Lodieu · Marie Martig · Marcelo M. Miller Bertolami · Joey S.G. Mombarg · Juan Carlos Morales · Andr´esMoya · Benard Nsamba · KreˇsimirPavlovski · May G. Pedersen · Ignasi Ribas · Fabian R.N. Schneider · Victor Silva Aguirre · Keivan G. Stassun · Eline Tolstoy · Pier-Emmanuel Tremblay · Konstanze Zwintz Received: date / Accepted: date A. Serenelli Institute of Space Sciences (ICE, CSIC), Carrer de Can Magrans S/N, Bellaterra, E- 08193, Spain and Institut d'Estudis Espacials de Catalunya (IEEC), Carrer Gran Capita 2, Barcelona, E-08034, Spain E-mail: [email protected] A. Weiss Max Planck Institute for Astrophysics, Karl Schwarzschild Str. 1, Garching bei M¨unchen, D-85741, Germany C. Aerts Institute of Astronomy, Department of Physics & Astronomy, KU Leuven, Celestijnenlaan 200 D, 3001 Leuven, Belgium and Department of Astrophysics, IMAPP, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen, the Netherlands G.C. Angelou Max Planck Institute for Astrophysics, Karl Schwarzschild Str. 1, Garching bei M¨unchen, D-85741, Germany D. Baroch J. C. Morales I. Ribas Institute of· Space Sciences· (ICE, CSIC), Carrer de Can Magrans S/N, Bellaterra, E-08193, arXiv:2006.10868v2 [astro-ph.SR] 9 Apr 2021 Spain and Institut d'Estudis Espacials de Catalunya (IEEC), C/Gran Capit`a2-4, E-08034 2 Serenelli, Weiss, Aerts et al. -
FY13 High-Level Deliverables
National Optical Astronomy Observatory Fiscal Year Annual Report for FY 2013 (1 October 2012 – 30 September 2013) Submitted to the National Science Foundation Pursuant to Cooperative Support Agreement No. AST-0950945 13 December 2013 Revised 18 September 2014 Contents NOAO MISSION PROFILE .................................................................................................... 1 1 EXECUTIVE SUMMARY ................................................................................................ 2 2 NOAO ACCOMPLISHMENTS ....................................................................................... 4 2.1 Achievements ..................................................................................................... 4 2.2 Status of Vision and Goals ................................................................................. 5 2.2.1 Status of FY13 High-Level Deliverables ............................................ 5 2.2.2 FY13 Planned vs. Actual Spending and Revenues .............................. 8 2.3 Challenges and Their Impacts ............................................................................ 9 3 SCIENTIFIC ACTIVITIES AND FINDINGS .............................................................. 11 3.1 Cerro Tololo Inter-American Observatory ....................................................... 11 3.2 Kitt Peak National Observatory ....................................................................... 14 3.3 Gemini Observatory ........................................................................................