Discovery of a pre-cataclysmic binary with unusual chromaticity of the eclipsed white dwarf by the GPX survey

ABSTRACT We report the discovery of a relatively bright eclipsing binary system, which consists of a white dwarf (WD) and a main-sequence K7 star with clear signs of chromospheric and spot activity. The light curve of this system shows ∼0.2 mag ellipsoidal variability with a period of 0.297549 d and a short total eclipse of the WD. Based on our analysis of the spectral and photometric data, we estimated the parameters of the system. The K7V star is tidally deformed but does not fill its Roche lobe (the filling factor is about 0.86). The orbital inclination is i = $73{_{.}^{\circ}}1 \pm 0{_{.}^{\circ}}2$, and the mass ratio is q = M2/M1 ≈ 0.88. The parameters of the K7V star are M2 ≈ 0.64 M⊙, R2 = 0.645 ± 0.012R⊙, and T2 ≈ 4070 K. The parameters of the WD are M1 ≈ 0.72 M⊙, R1 = 0.013 ± 0.003R⊙, and T1 = 8700 ± 1100 K. Photometric observations in different bands revealed that the maximum depth of the eclipse is in the SDSS r filter, which is unusual for a system of a WD and a late main-sequence star. We suspect that this system is a product of the evolution of a common-envelope binary star, and that the WD accretes the stellar wind from the secondary star (the so-called low-accretion-rate polar, hereafter LARP).

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Close Binary (and Pulsating) Nuclei of Planetary Nebulae

International Astronomical Union Colloquium ◽

10.1017/s0252921100076028 ◽

1979 ◽

Vol 53 ◽

pp. 266-268

Author(s):

Howard E. Bond

Keyword(s):

Angular Momentum ◽

White Dwarf ◽

Main Sequence ◽

Planetary Nebulae ◽

Close Binary ◽

Common Envelope ◽

Secondary Star ◽

Cataclysmic Binaries ◽

Red Giant ◽

Central Stars

Close-binary central stars of planetary nebulae are of interest to participants in this Colloquium because of recent suggestions that the cataclysmic binaries, containing a white dwarf and a lower-main-sequence star, may be descended from such objects (e.g. Paczynski 1976; Ritter 1976; Webbink 1978; Meyer and Meyer-Hofmeister 1978; Livio, Salzman, and Shaviv 1979). The proposed scenario is. that a binary system of initially large separation (P.= 1-10 yr) forms a “common-envelope” binary after the primary has evolved to the red-giant stage and developed a degenerate core. The secondary star spirals inward inside the red-giant envelope, eventually transferring enough angular momentum to the envelope to eject it. The result is a close binary containing the hot degenerate core of the red giant and a cool main-sequence companion, surrounded by the ejected envelope, which is ionized by the hotter star. Much later, when the cool companion begins to evolve, it will start to transfer matter to the hot star (by now a white dwarf), and cataclysmic activity ensues.

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Fluorescence and Chromospheric Activity of V471 Tau

International Astronomical Union Colloquium ◽

10.1017/s0252921100001366 ◽

2002 ◽

Vol 187 ◽

pp. 167-172

Author(s):

T.R. Vaccaro ◽

R.E. Wilson

Keyword(s):

Light Curve ◽

Radial Velocity ◽

Orbital Period ◽

White Dwarf ◽

Binary Star ◽

Star Model ◽

Orbital Inclination ◽

Orbital Parameters ◽

Maximum Emission ◽

Chromospheric Activity

AbstractThe red dwarf + white dwarf eclipsing binary V471 Tau shows a variable Hα feature that varies from absorption during eclipse to maximum emission during white dwarf transit. In 1998 we obtained simultaneous BVRI photometry and Hα spectroscopy, with thorough phase coverage of the 12.5 hour orbital period. A binary star model was used with our light curve, radial velocity, and Hα data to refine stellar and orbital parameters. Combined absorption-emission profiles were generated by the model and fit to the observations, yielding a red star radius of 0.94R⊙. Orbital inclination 78° is required with this size and other known parameters. The model includes three spots 1,000 K cooler than the surrounding photosphere. The variable Hα profile was modeled as a chromospheric fluorescing region (essentially on the surface of the red star) centered at the substellar point. Additional emission seen outside our modeled profiles may be large co-rotating prominences that complicate the picture.

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Post-common-envelope binaries from SDSS - I. 101 white dwarf main-sequence binaries with multiple Sloan Digital Sky Survey spectroscopy

Monthly Notices of the Royal Astronomical Society ◽

10.1111/j.1365-2966.2007.12288.x ◽

2007 ◽

Vol 382 (4) ◽

pp. 1377-1393 ◽

Cited By ~ 97

Author(s):

A. Rebassa-Mansergas ◽

B. T. Gänsicke ◽

P. Rodríguez-Gil ◽

M. R. Schreiber ◽

D. Koester

Keyword(s):

White Dwarf ◽

Main Sequence ◽

Sloan Digital Sky Survey ◽

Common Envelope ◽

Sky Survey

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Cataclysmic Variable Stars

Highlights of Astronomy ◽

10.1017/s1539299600019924 ◽

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.

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Revised Stellar Parameters for V471 Tau, A Post-common Envelope Binary in the Hyades

The Astronomical Journal ◽

10.3847/1538-3881/ac390f ◽

2021 ◽

Vol 163 (1) ◽

pp. 34

Author(s):

Philip S. Muirhead ◽

Jason Nordhaus ◽

Maria R. Drout

Keyword(s):

White Dwarf ◽

Main Sequence ◽

Hubble Space Telescope ◽

Main Sequence Star ◽

Velocity Measurements ◽

Single Star ◽

Orbital Parameters ◽

Common Envelope ◽

Star Evolution ◽

First Time

Abstract V471 Tau is a post-common-envelope binary consisting of an eclipsing DA white dwarf and a K-type main-sequence star in the Hyades star cluster. We analyzed publicly available photometry and spectroscopy of V471 Tau to revise the stellar and orbital parameters of the system. We used archival K2 photometry, archival Hubble Space Telescope spectroscopy, and published radial-velocity measurements of the K-type star. Employing Gaussian processes to fit for rotational modulation of the system flux by the main-sequence star, we recovered the transits of the white dwarf in front of the main-sequence star for the first time. The transits are shallower than would be expected from purely geometric occultations owing to gravitational microlensing during transit, which places an additional constraint on the white-dwarf mass. Our revised mass and radius for the main-sequence star is consistent with single-star evolutionary models given the age and metallicity of the Hyades. However, as noted previously in the literature, the white dwarf is too massive and too hot to be the result of single-star evolution given the age of the Hyades, and may be the product of a merger scenario. We independently estimate the conditions of the system at the time of common envelope that would result in the measured orbital parameters today.

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Maximum mass ratio of am CVn-type binary systems and maximum white dwarf mass in ultra-compact x-ray binaries (addendum - Serb. Astron. J. No. 183 (2011), 63)

Serbian Astronomical Journal ◽

10.2298/saj1284105a ◽

2012 ◽

pp. 105-107

Author(s):

B. Arbutina

Keyword(s):

Mass Transfer ◽

White Dwarf ◽

Binary Systems ◽

Accretion Rate ◽

Practical Relevance ◽

Maximum Mass ◽

Mass Ratio ◽

X Ray ◽

The Stability ◽

X Ray Binaries

We recalculated the maximum white dwarf mass in ultra-compact X-ray binaries obtained in an earlier paper (Arbutina 2011), by taking the effects of super-Eddington accretion rate on the stability of mass transfer into account. It is found that, although the value formally remains the same (under the assumed approximations), for white dwarf masses M2 >~0.1MCh mass ratios are extremely low, implying that the result for Mmax is likely to have little if any practical relevance.

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The criteria for dynamical mass transfer of the main-sequence donor stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312019679 ◽

2012 ◽

Vol 8 (S290) ◽

pp. 213-214

Author(s):

H. Ge ◽

R. F. Webbink ◽

X. Chen ◽

Z. Han

Keyword(s):

Mass Transfer ◽

Main Sequence ◽

Critical Mass ◽

Mass Ratio ◽

Dynamical Mass ◽

Common Envelope ◽

Binary Evolution ◽

Evolutionary Fate

AbstractMass transfer is very common in binary evolution and it dominates the evolutionary fate of binaries. Two crucial problems i.e. dynamical mass transfer and common envelope evolution, are not well understood yet. Here we focus on the first problem, and systematically show the critical mass ratio for dynamical mass transfer when the donor stars are still on the main sequence (MS).

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Nova Models and their Problems

International Astronomical Union Colloquium ◽

10.1017/s0252921100069475 ◽

1977 ◽

Vol 42 ◽

pp. 301-310

Author(s):

H.-C. Thomas

Keyword(s):

White Dwarf ◽

Main Sequence ◽

Main Sequence Star ◽

Late Type ◽

Hydrogen Bomb ◽

Binary Model ◽

Photometric Observations

Very detailed spectroscopic and photometric observations of Novae are available today. Unfortunately they do not directly tell us what suddenly makes a star a million times brighter, sometimes even transforming the familiar constellations on the sky. Twenty-five years after its publication, Mestel’s (1952) metaphor of a gigantic hydrogen bomb seems to be most widely accepted, although he at that time applied his model to a Supernova outburst. Later Giannone and Weigert (1967) as well as Rose (1968), Saslaw (1968) and others have computed hydrostatic models of such an event, using Kraft’s (1963) binary model of a late type main sequence star and a white dwarf. Detailed hydrodynamic computations were carried out by Starrfield and his collaborators (for references see Sparks, Starrfield, and Truran, 1977) and recently by Prialnik, Shara, and Shaviv (A & A 62, 339, 1978).

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The Stein 2051 System

International Astronomical Union Colloquium ◽

10.1017/s0252921100052490 ◽

1977 ◽

Vol 33 ◽

pp. 93-93

Author(s):

K. Aa. Strand

Keyword(s):

Spectral Type ◽

White Dwarf ◽

Orbital Motion ◽

Binary Star ◽

Major Axis ◽

Mass Ratio ◽

Semi Major Axis ◽

Naval Observatory ◽

Red Dwarfs ◽

The Individual

AbstractAn investigation is currently being made of the parallax, proper motion, orbital motion, and mass ratio of the nearby binary star Stein 2051 [04h 11m.4, + 58°49’; (1900); mv = 11.08 and 12.44] based upon photographs taken with the Sproul Observatory 61-cm refractor, the 155-cm astrometric reflector of the U.S. Naval Observatory, and the 33-cm Vatican Carte du Ciel astrograph.A parallax of 0”185 reduced to absolute has been obtained from the material of the Sproul and Naval Observatories which covers the period 1965 to 1975.Since an arc of only 64° in the orbital motion of the visible components has been described from the 1908 epoch of the earliest Vatican plate, and since the separation has increased from 6.” 3 at that time to 7.“ 3 at present and still on the increase, the period of the orbit can only be roughly estimated to be in excess of 300 years.With all plates measured in the same reference frame it has been possible to determine the individual motions of the two components and the mass ratio between them. Preliminary results indicate a perturbation in the orbital motion of the red component with a period of 20 years and a semi-major axis of 0’.’065. The mass ratio between the red dwarf system and the white dwarf is 0.5.A mass of 0.22 M⊙ of the red component has been determined based upon comparison of its luminosity (Mv = 12.42) with the red dwarfs Krüger 60 A (Mv = 11.82), o2 Eri C (Mv = 12.73) and Krüger 60 B (Mv = 13.48) which have the same spectral type (M4) and known masses of 0.26, 0.19, and 0.16 respectively in units of solar masses. Its dark compainion has a mass of 0.02 M⊙ The white dwarf of spectral type DC and Mv = 13.78 has a mass of 0.48 M⊙ as determined from the mass ratio of 0.5 mentioned above.

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