scholarly journals Constraints on the Atmospheric Parameters of the Binary DA White Dwarf L870-2 (EG11)

1989 ◽  
Vol 114 ◽  
pp. 435-439
Author(s):  
P. Bergeron ◽  
F. Wesemael ◽  
J. Liebert ◽  
G. Fontaine ◽  
P. Lacombe
Keyword(s):  
Observational Data ◽  
Stellar Evolution ◽  
Effective Temperature ◽  
White Dwarf ◽  
Binary Systems ◽  
Absolute Magnitude ◽  
Atmospheric Parameters ◽  
Spectroscopic Binary ◽  
Short Period ◽  
Period System

The recent discovery that the cool DA white dwarf L870-2 (EG11, WD0135-052) is a double-lined spectroscopic binary composed of a detached pair of DA white dwarfs (Saffer, Liebert, and Olszewski 1988, SLO hereafter) has raised some challenging problems for stellar evolution theories of such binary systems. One first important step in the understanding of this short-period system is to establish the atmospheric parameters of each component. SLO have argued from previous determinations of the effective temperature and absolute magnitude of the system, and also from their own study of the composite Hα profile, that the two components should be similar. We wish here to reexamine this assertion by taking a new look at the constraints on the two components brought about by the available observational data.

scholarly journals The history of KZ Hya and its unseen companions

2008 ◽  
Vol 4 (S252) ◽  
pp. 421-422
Author(s):  
S. Y. Jiang
Keyword(s):  
Effective Temperature ◽  
White Dwarf ◽  
Main Sequence ◽  
Absolute Magnitude ◽  
High Amplitude ◽  
Mass Star ◽  
Solar Mass ◽  
Short Period ◽  
Outer Atmosphere ◽  
Rich Material

AbstractKZ Hya is a short-period high amplitude metal pool population II pulsating variable. Its spectral type is B9-A7 III/IV. Its average effective temperature is 7640K. But its mass is only 0.97 solar mass. From normal stellar evolution and H-R diagram, we can not get such a solar mass star at post main sequence stage with so high effective temperature and so early type spectra. We observe this star since 1984 till now, 23years past. Finally we prove it is inside a binary with at least 2 unseen companions. The most massive companion has mass larger than 0.76 solar mass, mostly may be 0.99 to 3.99 solar mass. That means this companion must be a massive white dwarf. The distance between tow companions is about 10 AU. If the companion is white dwarf, this binary are fairly inside the nebula. This system is very old, older than 7.59 billion years. The nebula should be already diluted to very low density so that we can see the nebula directly. As its spectra type is B9III/VI at some time of maximum light and the visual absolute magnitude is 2.78, about 2 magnitudes higher than our sun. We can image that at the end of AGB stage of the companion, the strong fast winds from hot central core push away the outer atmosphere of KZ Hya. Later KZ Hya absorbed a part of Helium rich material from the companion. This will cause hydrogen content X decrease from 0.75 to about 0.62. Then KZ Hya looks like a hot post main sequence star

scholarly journals 14. White Dwarf Atmospheres

1971 ◽  
Vol 42 ◽  
pp. 81-96 ◽  
Author(s):  
V. Weidemann
Keyword(s):  
Chemical Composition ◽  
Observational Data ◽  
Effective Temperature ◽  
White Dwarf ◽  
General Information ◽  
Stellar Atmospheres ◽  
Surface Gravity ◽  
Atmospheric Parameters

We first consider the general information scheme for the interpretation of observational data (Figure 1). From the relations plotted it is evident that (in going from left to right) this scheme can only be solved if distances are known and if we are able to determine the atmospheric parameters: effective temperature, Teff, surface gravity, g, and chemical composition from observations of colors and spectra – which is the genuine task of the theory of stellar atmospheres.

scholarly journals Two new double-lined spectroscopic binary white dwarfs

2020 ◽  
Vol 493 (2) ◽  
pp. 2805-2816 ◽  
Author(s):  
Mukremin Kilic ◽  
A Bédard ◽  
P Bergeron ◽  
Alekzander Kosakowski
Keyword(s):  
Radial Velocity ◽  
White Dwarf ◽  
White Dwarfs ◽  
Binary Systems ◽  
Mass Ratio ◽  
Orbital Parameters ◽  
Long Period ◽  
Spectroscopic Binary ◽  
Velocity Variations ◽  
Period System

ABSTRACT We present radial velocity observations of four binary white dwarf candidates identified through their overluminosity. We identify two new double-lined spectroscopic binary systems, WD 0311–649 and WD 1606+422, and constrain their orbital parameters. WD 0311–649 is a 17.7 h period system with a mass ratio of 1.44 ± 0.06 and WD 1606+422 is a 20.1 h period system with a mass ratio of 1.33 ± 0.03. An additional object, WD 1447–190, is a 43 h period single-lined white dwarf binary, whereas WD 1418–088 does not show any significant velocity variations over time-scales ranging from minutes to decades. We present an overview of the 14 overluminous white dwarfs that were identified by Bédard et al., and find the fraction of double- and single-lined systems to be both 31 per cent. However, an additional 31 per cent of these overluminous white dwarfs do not show any significant radial velocity variations. We demonstrate that these must be in long-period binaries that may be resolved by Gaia astrometry. We also discuss the overabundance of single low-mass white dwarfs identified in the SPY survey, and suggest that some of those systems are also likely long-period binary systems of more massive white dwarfs.

scholarly journals The Search for Close Binary Evolved Stars

1989 ◽  
Vol 114 ◽  
pp. 408-412
Author(s):  
Rex A. Saffer ◽  
James Liebert
Keyword(s):  
Binary System ◽  
White Dwarf ◽  
White Dwarfs ◽  
Binary Systems ◽  
Close Binary ◽  
Brown Dwarf ◽  
Null Results ◽  
Spectroscopic Observations ◽  
Evolved Stars ◽  
Short Period

AbstractWe report on a search for short-period binary systems composed of pairs of evolved stars. The search is being carried out concurrently with a program to characterize the kinematical properties of two different samples of stars. Each sample has produced one close binary candidate for which further spectroscopic observations are planned. We also recapitulate the discovery of a close detached binary system composed of two cool DA white dwarfs, and we discuss the null results of Hα observations of the suspected white dwarf/brown dwarf system G 29–38.

scholarly journals Cataclysmic Variable Stars

1998 ◽  
Vol 11 (1) ◽  
pp. 16-27
Author(s):  
Brian Warner
Keyword(s):  
White Dwarf ◽  
Binary Systems ◽  
Main Sequence ◽  
Variable Stars ◽  
Cataclysmic Variable ◽  
Common Envelope ◽  
Short Period ◽  
Orbital Periods ◽  
Probable Origin ◽  
Binary Orbit

The evolution of single stars on and away from the main sequence is well understood. A degenerate core is formed in a star as the star leaves the main sequence and expands to a giant with a radius typically 50 - 500 Ro . Observationally it is known that most stars are members of binary systems, and among these many have orbital periods less than 100 y. It can happen, therefore, that the expanding envelope of the primary of a binary system can reach to the secondary. As this happens, the primary fills its Roche tidal lobe and transfers matter to the secondary; if the primary has a radiative envelope the rate at which this occurs exceeds the Eddington limit of the secondary, which therefore repels the incoming gas, forming a common envelope around the two stars. Friction within the envelope causes the stars to spiral towards each other until the energy and angular momentum extracted from the binary orbit and transferred to the envelope are sufficient to eject the common envelope as a planetary nebula, leaving a short period binary comprising a white dwarf and a main sequence star. This mechanism of producing short period binaries containing white dwarfs, proposed by Ostriker and by Paczynski (1976), is the probable origin of the class of objects known as Cataclysmic Variable Stars (CVs), which encompass the classical novae, dwarf novae, novalike variables and a variety of related objects. Evidence has been accumulating for forty years (Crawford & Kraft 1956, Warner 1995a) that every CV consists of a secondary star (usually a dwarf, but a few systems contain giants) filling its Roche lobe and transferring mass to a white dwarf primary. In systems of normal chemical composition the orbital periods lie between 75 mins and ~250 d, with the majority having . A few hydrogen-free systems are known for which 17 mins < Porb < 50 mins. It should be noted that CVs are very compact binary systems: for h such a binary would fit inside the Sun.

scholarly journals A catalogue of white dwarfs in Gaia EDR3

2021 ◽  
Author(s):  
N P Gentile Fusillo ◽  
P-E Tremblay ◽  
E Cukanovaite ◽  
A Vorontseva ◽  
R Lallement ◽  
...  
Keyword(s):  
Effective Temperature ◽  
White Dwarf ◽  
Proper Motion ◽  
White Dwarfs ◽  
Absolute Magnitude ◽  
Sloan Digital Sky Survey ◽  
Atmospheric Models ◽  
Sky Survey ◽  
Cross Match ◽  
Temperature Surface

Abstract We present a catalogue of white dwarf candidates selected from Gaia early data release three (EDR3). We applied several selection criteria in absolute magnitude, colour, and Gaia quality flags to remove objects with unreliable measurements while preserving most stars compatible with the white dwarf locus in the Hertzsprung-Russell diagram. We then used a sample of over 30 000 spectroscopically confirmed white dwarfs and contaminants from the Sloan Digital Sky Survey (SDSS) to map the distribution of these objects in the Gaia absolute magnitude-colour space. Finally, we adopt the same method presented in our previous work on Gaia DR2 to calculate a probability of being a white dwarf (PWD) for ≃ 1.3 million sources which passed our quality selection. The PWD values can be used to select a sample of ≃ 359 000 high-confidence white dwarf candidates. We calculated stellar parameters (effective temperature, surface gravity, and mass) for all these stars by fitting Gaia astrometry and photometry with synthetic pure-H, pure-He and mixed H-He atmospheric models. We estimate an upper limit of 93 per cent for the overall completeness of our catalogue for white dwarfs with G ≤ 20 mag and effective temperature (Teff) &gt;7000 K, at high Galactic latitudes (|b| &gt; 20○). Alongside the main catalogue we include a reduced-proper-motion extension containing ≃ 10 200 white dwarf candidates with unreliable parallax measurements which could, however be identified on the basis of their proper motion. We also performed a cross-match of our catalogues with SDSS DR16 spectroscopy and provide spectral classification based on visual inspection for all resulting matches.

scholarly journals GD 424 – a helium-atmosphere white dwarf with a large amount of trace hydrogen in the process of digesting a rocky planetesimal

2020 ◽  
Author(s):  
Paula Izquierdo ◽  
Odette Toloza ◽  
Boris T Gänsicke ◽  
Pablo Rodríguez-Gil ◽  
Jay Farihi ◽  
...  
Keyword(s):  
Steady State ◽  
Effective Temperature ◽  
White Dwarf ◽  
Metal Pollution ◽  
White Dwarfs ◽  
Surface Gravity ◽  
Atmospheric Composition ◽  
Atmospheric Parameters ◽  
Hybrid Analysis ◽  
Helium Atmosphere

Abstract The photospheric metal pollution of white dwarfs is now well-established as the signature of the accretion of planetary debris. However, the origin of the trace hydrogen detected in many white dwarfs with helium atmospheres is still debated. Here, we report the analysis of GD 424: a metal-polluted, helium-atmosphere white dwarf with a large amount of trace hydrogen. We determined the atmospheric parameters using a hybrid analysis that combines the sensitivity of spectroscopy to the atmospheric composition, log (H/He), with that of photometry and astrometry to the effective temperature, Teff, and surface gravity, log g. The resulting white dwarf mass, radius, and cooling age are ${M_{\rm{WD}}}=0.77\pm 0.01\, {\rm{M}_{\odot}}$, ${R_{\rm{WD}}}=0.0109\pm 0.0001\, {\rm{R}_{\odot}}$, and τcool = 215 ± 10 Myr, respectively. We identified and measured the abundances of 11 photospheric metals and argue that the accretion event is most likely either in the increasing or steady state, and that the disrupted planetesimal resembles either CI chondrites or the bulk Earth in terms of its composition. We suggest that the observed 1.33 × 1022 g of trace hydrogen in GD 424 were at least partly acquired through accretion of water-rich planetary debris in an earlier accretion episode.

scholarly journals Links between Symbiotic and Planetary Nebulae

2004 ◽  
Vol 194 ◽  
pp. 226-227 ◽  
Author(s):  
J. A. López ◽  
K. Escalante ◽  
H. Riesgo-Tirado
Keyword(s):  
Stellar Evolution ◽  
White Dwarf ◽  
Binary Systems ◽  
Large Fraction ◽  
Planetary Nebulae ◽  
Central Star ◽  
Primary Component ◽  
Binary Evolution ◽  
Gaseous Envelope

Planetary nebulae (PNe) represent a well defined stage of stellar evolution, where the characteristics of both, the central star and the gaseous envelope have defined properties. A large fraction of PNe contain binary nuclei, therefore, binary evolution plays an important role in the AGB and proto-planetary stages under certain circumstances. Symbiotic nebulae with extended envelopes (D-type), are identified with binary systems where the primary component is usually a Mira giant and the companion a hot white dwarf. Some of these systems resemble planetary nebulae and as a consequence can lead to misleading interpretations. Here we discuss some relevant links and differences between these two types of nebulae.

scholarly journals Evolutionary Trends in Wide Binary Systems

1982 ◽  
Vol 69 ◽  
pp. 81-103
Author(s):  
Peter van de Kamp
Keyword(s):  
Stellar Evolution ◽  
White Dwarf ◽  
Binary Stars ◽  
Binary Systems ◽  
Main Sequence ◽  
Evolutionary Trends ◽  
Wide Binary ◽  
The Past ◽  
Past Half Century ◽  
Past Half

Zdenek Kopal has kindly invited me, and I have accepted, to “instruct the theoreticians on known facts”. He also asked me to express my opinion on the relative evolutionary stages of components.I am essentially an observing astronomer, occupied with stars in our immediate neighborhood, say within 10 or at most some 25 parsec, i.e., the lower main sequence and the white dwarf degenerate branch.I hope that I may perhaps contribute by surveying and reporting some relevant data. I shall touch on a number of topics, limited because of selection and lack of knowledge. My contributions to binary stars lie in the realm of parallaxes, mass-ratios and masses, – and for the past half century, perturbations, interpreted as unseen companions, stellar and otherwise. I shall briefly report on some results, and I shall be wondering and hoping that some trace of stellar evolution may possibly be present in these results. After having witnessed for more than half a century my own astronomical evolution, the time has come for me to become more aware of theoretical, evolutionary and cosmological aspects of the cosmic material, I have been playing with so long.

Sign in / Sign up

Export Citation Format

Share Document