Redalyc.Ages of White Dwarf-Red Subdwarf Systems
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Meet the Family
Open Astronomy 2014; 1 Research Article Open Access Stephan Geier*, Roy H. Østensen, Peter Nemeth, Ulrich Heber, Nicola P. Gentile Fusillo, Boris T. Gänsicke, John H. Telting, Elizabeth M. Green, and Johannes Schaffenroth Meet the family − the catalog of known hot subdwarf stars DOI: DOI Received ..; revised ..; accepted .. Abstract: In preparation for the upcoming all-sky data releases of the Gaia mission, we compiled a catalog of known hot subdwarf stars and candidates drawn from the literature and yet unpublished databases. The catalog contains 5613 unique sources and provides multi-band photometry from the ultraviolet to the far infrared, ground based proper motions, classifications based on spectroscopy and colors, published atmospheric parameters, radial velocities and light curve variability information. Using several different techniques, we removed outliers and misclassified objects. By matching this catalog with astrometric and photometric data from the Gaia mission, we will develop selection criteria to construct a homogeneous, magnitude-limited all-sky catalog of hot subdwarf stars based on Gaia data. As first application of the catalog data, we present the quantitative spectral analysis of 280 sdB and sdOB stars from the Sloan Digital Sky Survey Data Release 7. Combining our derived parameters with state-of-the-art proper motions, we performed a full kinematic analysis of our sample. This allowed us to separate the first significantly large sample of 78 sdBs and sdOBs belonging to the Galactic halo. Comparing the properties of hot subdwarfs from the disk and the halo with hot subdwarf samples from the globular clusters ω Cen and NGC2808, we found the fraction of intermediate He-sdOBs in the field halo population to be significantly smaller than in the globular clusters. -
The X-Ray Universe 2017 List of Posters
The X-ray Universe 2017 List of Posters A - Solar System, Exoplanets and Star-Planet-Interaction A01 Frederic Marin Transmitted and polarized scattered fluxes by the exoplanet HD 189733b in X-rays B - Star formation, Young Stellar Objects, Cool and Hot Stars B01 Yael Naze A legacy survey of early B-type stars using the RGS B02 Stefan Czesla The coronae of Kepler superflare stars B03 Mauricio Elías Chávez ESTIMATION OF THE STAR FORMATION RATE (SFR) THROUGH DATA ANALYSIS OF SWIFT'S LONG- GRBs FROM 2008 TO 2017 B04 Federico Fraschetti Local protoplanetary disk ionisation by T Tauri star energetic particles B05 Martin A. Guerrero The XMM-Newton View of Wolf-Rayet Bubbles B06 Sandro Mereghetti X-rays as a new tool to study the winds of hot subdwarf stars B07 Yael Naze Zeta Pup variability revisited B08 John Pye A survey of long-term X-ray variability in cool stars B09 Gregor Rauw The flaring activity of pre-main sequence stars in NGC6530 B10 Beate Stelzer Activity and rotation of the X-ray emitting Kepler stars B11 Beate Stelzer Calibrating the time-evolution of the X-ray emission of M dwarfs C - White Dwarfs, Cataclysmic Variables and Novae C01 Andrej Dobrotka XMM-Newton observation of nova like system MV Lyr and search for source of the fast variability detected in Kepler data C02 Cigdem Gamsizkan Reanalysis of high-resolution XMM-Newton data of V2491 Cygni using models of collisionally ionized hot absorbers C03 Isabel J. Lima Simultaneous modelling of X-ray emission and optical polarization of intermediate polars: the case of V405 Aur C04 Arti Joshi XMM-Newton observations of an asynchronously rotating polar CD Ind C05 Sandro Mereghetti The mysterious companion of the hot subdwarf HD 49798 C06 Nasrin Talebpour X-ray Spectra of the Cataclysmic Variable LS Peg using XMM-Newton and SWIFT data Sheshvan D - Isolated Neutron Stars & Magnetars D01 Jaziel G. -
Brown Dwarf: White Dwarf: Hertzsprung -Russell Diagram (H-R
Types of Stars Spectral Classifications: Based on the luminosity and effective temperature , the stars are categorized depending upon their positions in the HR diagram. Hertzsprung -Russell Diagram (H-R Diagram) : 1. The H-R Diagram is a graphical tool that astronomers use to classify stars according to their luminosity (i.e. brightness), spectral type, color, temperature and evolutionary stage. 2. HR diagram is a plot of luminosity of stars versus its effective temperature. 3. Most of the stars occupy the region in the diagram along the line called the main sequence. During that stage stars are fusing hydrogen in their cores. Various Types of Stars Brown Dwarf: White Dwarf: Brown dwarfs are sub-stellar objects After a star like the sun exhausts its nuclear that are not massive enough to sustain fuel, it loses its outer layer as a "planetary nuclear fusion processes. nebula" and leaves behind the remnant "white Since, comparatively they are very cold dwarf" core. objects, it is difficult to detect them. Stars with initial masses Now there are ongoing efforts to study M < 8Msun will end as white dwarfs. them in infrared wavelengths. A typical white dwarf is about the size of the This picture shows a brown dwarf around Earth. a star HD3651 located 36Ly away in It is very dense and hot. A spoonful of white constellation of Pisces. dwarf material on Earth would weigh as much as First directly detected Brown Dwarf HD 3651B. few tons. Image by: ESO The image is of Helix nebula towards constellation of Aquarius hosts a White Dwarf Helix Nebula 6500Ly away. -
Detection and Characterization of Hot Subdwarf Companions of Massive Stars Luqian Wang
Georgia State University ScholarWorks @ Georgia State University Physics and Astronomy Dissertations Department of Physics and Astronomy 8-13-2019 Detection And Characterization Of Hot Subdwarf Companions Of Massive Stars Luqian Wang Follow this and additional works at: https://scholarworks.gsu.edu/phy_astr_diss Recommended Citation Wang, Luqian, "Detection And Characterization Of Hot Subdwarf Companions Of Massive Stars." Dissertation, Georgia State University, 2019. https://scholarworks.gsu.edu/phy_astr_diss/119 This Dissertation is brought to you for free and open access by the Department of Physics and Astronomy at ScholarWorks @ Georgia State University. It has been accepted for inclusion in Physics and Astronomy Dissertations by an authorized administrator of ScholarWorks @ Georgia State University. For more information, please contact [email protected]. DETECTION AND CHARACTERIZATION OF HOT SUBDWARF COMPANIONS OF MASSIVE STARS by LUQIAN WANG Under the Direction of Douglas R. Gies, PhD ABSTRACT Massive stars are born in close binaries, and in the course of their evolution, the initially more massive star will grow and begin to transfer mass and angular momentum to the gainer star. The mass donor star will be stripped of its outer envelope, and it will end up as a faint, hot subdwarf star. Here I present a search for the subdwarf stars in Be binary systems using the International Ultraviolet Explorer. Through spectroscopic analysis, I detected the subdwarf star in HR 2142 and 60 Cyg. Further analysis led to the discovery of an additional 12 Be and subdwarf candidate systems. I also investigated the EL CVn binary system, which is the prototype of class of eclipsing binaries that consist of an A- or F-type main sequence star and a low mass subdwarf. -
The Potential of Planets Orbiting Red Dwarf Stars to Support Oxygenic Photosynthesis and Complex Life
1 The Potential of Planets Orbiting Red Dwarf Stars to Support Oxygenic Photosynthesis and Complex Life Joseph Gale1 and Amri Wandel2 The Institute of Life Sciences1and The Racach Institute of Physics2, The Hebrew University of Jerusalem, 91904, Israel. [email protected] [email protected] Accepted for publication in the International Journal of Astrobiology Abstract We review and reassess the latest findings on the existence of extra-solar system planets and their potential of having environmental conditions that could support Earth-like life. Within the last two decades, the multi-millennial question of the existence of extra-Solar- system planets has been resolved with the discovery of numerous planets orbiting nearby stars, many of which are Earth-sized (and some even with moderate surface temperatures). Of particular interest in our search for clement conditions for extra-solar system life are planets orbiting Red Dwarf (RD) stars, the most numerous stellar type in the Milky Way galaxy. We show that including RDs as potential life supporting host stars could increase the probability of finding biotic planets by a factor of up to a thousand, and reduce the estimate of the distance to our nearest biotic neighbor by up to 10. We argue that multiple star systems need to be taken into account when discussing habitability and the abundance of biotic exoplanets, in particular binaries of which one or both members are RDs. Early considerations indicated that conditions on RD planets would be inimical to life, as their Habitable Zones (where liquid water could exist) would be so close as to make planets tidally locked to their star. -
A FEROS Survey of Hot Subdwarf Stars
Open Astron. 2018; 27: 7–13 Research Article Stéphane Vennes*, Péter Németh, and Adela Kawka A FEROS Survey of Hot Subdwarf Stars https://doi.org/10.1515/astro-2018-0005 Received Oct 02, 2017; accepted Nov 07, 2017 Abstract: We have completed a survey of twenty-two ultraviolet-selected hot subdwarfs using the Fiber-fed Extended Range Optical Spectrograph (FEROS) and the 2.2-m telescope at La Silla. The sample includes apparently single objects as well as hot subdwarfs paired with a bright, unresolved companion. The sample was extracted from our GALEX cat- alogue of hot subdwarf stars. We identified three new short-period systems (P = 3.5 hours to 5 days) and determined the orbital parameters of a long-period (P = 62d.66) sdO plus G III system. This particular system should evolve into a close double degenerate system following a second common envelope phase. We also conducted a chemical abundance study of the subdwarfs: Some objects show nitrogen and argon abundance excess with respect to oxygen. We present key results of this programme. Keywords: binaries: close, binaries: spectroscopic, subdwarfs, white dwarfs, ultraviolet: stars 1 Introduction ing a mass transfer event, i.e., comparable to the observed fraction (≈70%) of short period binaries (P < 10 d, Maxted et al. 2001; Morales-Rueda et al. 2003), while the remain- The properties of extreme horizontal branch (EHB) stars, ing single objects are formed by the merger of two helium i.e., the hot, hydrogen-rich (sdB) and helium-rich subd- white dwarfs which would also result in a thin hydrogen warf (sdO) stars, located at the faint blue end of the hori- layer. -
Massive Fast Rotating Highly Magnetized White Dwarfs: Theory and Astrophysical Applications
Massive Fast Rotating Highly Magnetized White Dwarfs: Theory and Astrophysical Applications Thesis Advisors Ph.D. Student Prof. Remo Ruffini Diego Leonardo Caceres Uribe* Dr. Jorge A. Rueda *D.L.C.U. acknowledges the financial support by the International Relativistic Astrophysics (IRAP) Ph.D. program. Academic Year 2016–2017 2 Contents General introduction 4 1 Anomalous X-ray pulsars and Soft Gamma-ray repeaters: A new class of pulsars 9 2 Structure and Stability of non-magnetic White Dwarfs 21 2.1 Introduction . 21 2.2 Structure and Stability of non-rotating non-magnetic white dwarfs 23 2.2.1 Inverse b-decay . 29 2.2.2 General Relativity instability . 31 2.2.3 Mass-radius and mass-central density relations . 32 2.3 Uniformly rotating white dwarfs . 37 2.3.1 The Mass-shedding limit . 38 2.3.2 Secular Instability in rotating and general relativistic con- figurations . 38 2.3.3 Pycnonuclear Reactions . 39 2.3.4 Mass-radius and mass-central density relations . 41 3 Magnetic white dwarfs: Stability and observations 47 3.1 Introduction . 47 3.2 Observations of magnetic white dwarfs . 49 3.2.1 Introduction . 49 3.2.2 Historical background . 51 3.2.3 Mass distribution of magnetic white dwarfs . 53 3.2.4 Spin periods of isolated magnetic white dwarfs . 53 3.2.5 The origin of the magnetic field . 55 3.2.6 Applications . 56 3.2.7 Conclusions . 57 3.3 Stability of Magnetic White Dwarfs . 59 3.3.1 Introduction . 59 3.3.2 Ultra-magnetic white dwarfs . 60 3.3.3 Equation of state and virial theorem violation . -
A Review on Substellar Objects Below the Deuterium Burning Mass Limit: Planets, Brown Dwarfs Or What?
geosciences Review A Review on Substellar Objects below the Deuterium Burning Mass Limit: Planets, Brown Dwarfs or What? José A. Caballero Centro de Astrobiología (CSIC-INTA), ESAC, Camino Bajo del Castillo s/n, E-28692 Villanueva de la Cañada, Madrid, Spain; [email protected] Received: 23 August 2018; Accepted: 10 September 2018; Published: 28 September 2018 Abstract: “Free-floating, non-deuterium-burning, substellar objects” are isolated bodies of a few Jupiter masses found in very young open clusters and associations, nearby young moving groups, and in the immediate vicinity of the Sun. They are neither brown dwarfs nor planets. In this paper, their nomenclature, history of discovery, sites of detection, formation mechanisms, and future directions of research are reviewed. Most free-floating, non-deuterium-burning, substellar objects share the same formation mechanism as low-mass stars and brown dwarfs, but there are still a few caveats, such as the value of the opacity mass limit, the minimum mass at which an isolated body can form via turbulent fragmentation from a cloud. The least massive free-floating substellar objects found to date have masses of about 0.004 Msol, but current and future surveys should aim at breaking this record. For that, we may need LSST, Euclid and WFIRST. Keywords: planetary systems; stars: brown dwarfs; stars: low mass; galaxy: solar neighborhood; galaxy: open clusters and associations 1. Introduction I can’t answer why (I’m not a gangstar) But I can tell you how (I’m not a flam star) We were born upside-down (I’m a star’s star) Born the wrong way ’round (I’m not a white star) I’m a blackstar, I’m not a gangstar I’m a blackstar, I’m a blackstar I’m not a pornstar, I’m not a wandering star I’m a blackstar, I’m a blackstar Blackstar, F (2016), David Bowie The tenth star of George van Biesbroeck’s catalogue of high, common, proper motion companions, vB 10, was from the end of the Second World War to the early 1980s, and had an entry on the least massive star known [1–3]. -
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 -
The Catalog of Known Hot Subdwarf Stars
Open Astron. 2017; 26: 164–168 Research Article Stephan Geier*, Roy H. Østensen, Peter Nemeth, Ulrich Heber, Nicola P. Gentile Fusillo, Boris T. Gänsicke, John H. Telting, Elizabeth M. Green, and Johannes Schaffenroth Meet the family − the catalog of known hot subdwarf stars https://doi.org/10.1515/astro-2017-0432 Received Sep 26, 2017; accepted Oct 23, 2017 Abstract: In preparation for the upcoming all-sky data releases of the Gaia mission, we compiled a catalog of known hot subdwarf stars and candidates drawn from the literature and yet unpublished databases. The catalog contains 5613 unique sources and provides multi-band photometry from the ultraviolet to the far infrared, ground based proper mo- tions, classifications based on spectroscopy and colors, published atmospheric parameters, radial velocities andlight curve variability information. Using several different techniques, we removed outliers and misclassified objects. By matching this catalog with astrometric and photometric data from the Gaia mission, we will develop selection crite- ria to construct a homogeneous, magnitude-limited all-sky catalog of hot subdwarf stars based on Gaia data. As first application of the catalog data, we present the quantitative spectral analysis of 280 sdB and sdOBstarsfrom the Sloan Digital Sky Survey Data Release 7. Combining our derived parameters with state-of-the-art proper motions, we performed a full kinematic analysis of our sample. This allowed us to separate the first significantly large sample of 78 sdBs and sdOBs belonging to the Galactic halo. Comparing the properties of hot subdwarfs from the disk and the halo with hot subdwarf samples from the globular clusters ω Cen and NGC 2808, we found the fraction of intermediate He-sdOBs in the field halo population to be significantly smaller than in the globular clusters. -
The Orbits of Subdwarf B + Main-Sequence Binaries I
A&A 548, A6 (2012) Astronomy DOI: 10.1051/0004-6361/201219723 & c ESO 2012 Astrophysics The orbits of subdwarf B + main-sequence binaries I. The sdB+G0 system PG 1104+243 J. Vos1, R. H. Østensen1,P.Degroote1,K.DeSmedt1,E.M.Green2,U.Heber3,H.VanWinckel1,B.Acke1, S. Bloemen1,P.DeCat4,K.Exter1, P. Lampens4, R. Lombaert1, T. Masseron5,J.Menu1,P.Neyskens5,G.Raskin1, E. Ringat6, T. Rauch6,K.Smolders1, and A. Tkachenko1 1 Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium e-mail: [email protected] 2 Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA 3 Dr. Remeis-Sternwarte Astronomisches Institut, Universität Erlangen-Nürnberg, 96049 Bamberg, Germany 4 Royal Observatory of Belgium, Ringlaan 3, 1180 Brussels, Belgium 5 Université Libre de Bruxelles, C.P. 226, Boulevard du Triomphe, 1050 Bruxelles, Belgium 6 Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany Received 31 May 2012 / Accepted 5 October 2012 ABSTRACT Context. The predicted orbital period histogram of a subdwarf B (sdB) population is bimodal with a peak at short (<10 days) and long (>250 days) periods. Observationally, however, there are many short-period sdB systems known, but only very few long-period sdB binaries are identified. As these predictions are based on poorly understood binary interaction processes, it is of prime importance to confront the predictions to well constrained observational data. We therefore initiated a monitoring program to find and characterize long-period sdB stars. Aims. In this contribution we aim to determine the absolute dimensions of the long-period binary system PG 1104+243 consisting of an sdB and a main-sequence (MS) component, and determine its evolution history. -
Hot Subdwarf Stars in Close-Up View: Orbits, Rotation, Abundances and Masses of Their Unseen Companions
Hot Subdwarf Stars in Close-up View: Orbits, Rotation, Abundances and Masses of their Unseen Companions Den Naturwissenschaftlichen Fakult¨aten der Friedrich-Alexander-Universit¨at Erlangen-N¨urnberg zur Erlangung des Doktorgrades vorgelegt von Stephan Geier aus Stadtsteinach Als Dissertation genehmigt von den Naturwissenschaftlichen Fakult¨aten der Universit¨at Erlangen-N¨urnberg Tag der m¨undlichen Pr¨ufung: 18. M¨arz 2009 Vositzender der Promotionskommission: Prof. Dr. E. B¨ansch Erstberichterstatter: Prof. Dr. U. Heber Zweitberichterstatter: Prof. Dr. P. Podsiadlowski, University of Oxford Drittberichterstatter: Prof. Dr. K. Werner, Universit¨at T¨ubingen Contents 1 Hot subdwarf stars: A review 9 1.1 Generalproperties ............................... .... 9 1.2 Single star formation and evolution scenarios . ............ 10 1.3 Hot subdwarf binaries: Observations, formation and evolution........... 12 1.4 Pulsating hot subdwarfs and asteroseismology . ............ 15 1.5 Hot subdwarf atmospheres and diffusion processes . .......... 20 1.6 Hot subdwarfs and extrasolar planets . ......... 21 1.7 Hotsubdwarfsashyper-velocitystars . ........ 23 1.8 Hot subdwarfs and globular clusters . ........ 24 1.9 Hot subdwarfs and the UV-upturn in early-type galaxies . ........... 25 1.10 Hot subdwarf stars, supernovae and cosmology . ........... 26 2 Hot subdwarf stars in close binary systems: Previous work and new discov- eries 30 2.1 Generalstatistics ............................... ..... 30 2.2 Determination of hot subdwarf and companion masses in close binaries . 33 2.3 Orbital parameters of new close binary subdwarfs . ........... 34 2.3.1 Target selection, observations and data reduction . ........... 35 2.3.2 Radial velocity measurements, power spectra and RV curves........ 35 2.3.3 Constraints on the nature of the unseen companions . ......... 36 2.3.4 Results ....................................