scholarly journals Nova Models and their Problems

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).

scholarly journals Photometry of AM Her Stars – Line and Continuum Emission

1979 ◽  
Vol 53 ◽  
pp. 324-328
Author(s):  
Paula Szkody
Keyword(s):  
Emission Line ◽  
White Dwarf ◽  
Main Sequence ◽  
Close Binary ◽  
Line Spectrum ◽  
Continuum Emission ◽  
Late Type ◽  
Emission Line Spectrum ◽  
Orbital Periods

The 4 known AM Her stars or polars (AM Her, ANUMa, W Pup, and 2A0311-227) are characterized by large circular polarizations of 10-35%, (Tapia 1977a, b, Krzeminski and Serkowski 1977), an emission line spectrum with strong H and He lines (Crampton and Cowley 1977, Greenstein et al. 1977), complex photometric variations (Szkody 1978, Priedhorsky and Krzeminski 1978, Warner & Nather 1972), long term high and low states and short orbital periods (80-180 min.). Models of these systems envision a close binary containing a magnetic white dwarf primary (B ~ 108G) and late type main sequence secondary transferring material into an accretion funnel over one or both poles of the white dwarf (Stockman et al. 1977, Lamb & Masters 1979, Liebert et al. 1978).

scholarly journals Evolution Models of Helium White Dwarf–Main-sequence Star Merger Remnants

2017 ◽  
Vol 835 (2) ◽  
pp. 242 ◽  
Author(s):  
Xianfei Zhang ◽  
Philip D. Hall ◽  
C. Simon Jeffery ◽  
Shaolan Bi
Keyword(s):  
White Dwarf ◽  
Main Sequence ◽  
Main Sequence Star

scholarly journals On the Separations of Common Proper Motion Binaries Containing White Dwarfs

1989 ◽  
Vol 114 ◽  
pp. 454-457
Author(s):  
T.D. Oswalt ◽  
E.M. Sion
Keyword(s):  
Mass Loss ◽  
White Dwarf ◽  
Proper Motion ◽  
White Dwarfs ◽  
Main Sequence ◽  
Late Type ◽  
Class A ◽  
Color Class

Luyten [1,2] and Giclas et al. [3,4] list over 500 known common proper motion binaries (CPMBs) which, on the basis of proper motion and estimated colors, are expected to contain at least one white dwarf (WD) component, usually paired with a late type main sequence (MS) star. Preliminary assessments of the CPMBs suggest that nearly all are physical pairs [5,6]. In this paper we address the issue of whether significant orbital expansion has occurred as a consequence of the post-MS mass loss expected to accompany the formation of the WDs in CPMBs.Though the CPMB sample remains largely unobserved, a spectroscopic survey of over three dozen CPMBs by Oswalt [5] found that nearly all faint components of Luyten and Giclas color class “a-f” and “+1”, respectively, or bluer were a WD. This tendency was also evident in a smaller sample studied by Greenstein [7]. Conversely, nearly all CPMBs having two components of color class “g-k” and “+3” or redder were MS+MS pairs. With the caveat that such criteria discriminate against CPMBs containing cool (but rare) WDs, they nonetheless provide a crude means of obtaining statistically significant samples for the comparison of orbital separations: 209 highly probable WD+MS pairs and 109 MS+MS pairs.

scholarly journals White dwarf-main sequence star collisions

1977 ◽  
Vol 179 (4) ◽  
pp. 705-718 ◽  
Author(s):  
M. M. Shara ◽  
G. Shaviv
Keyword(s):  
White Dwarf ◽  
Main Sequence ◽  
Main Sequence Star

scholarly journals Origin and Radial Distribution of Faint Blue Horizontal-Branch Stars

1988 ◽  
Vol 126 ◽  
pp. 679-680
Author(s):  
Charles D. Bailyn ◽  
Jonathan E. Grindlay ◽  
Haldan Cohn ◽  
Phyllis M. Lugger
Keyword(s):  
Radial Distribution ◽  
White Dwarf ◽  
Main Sequence ◽  
Main Sequence Star ◽  
Horizontal Branch ◽  
Horizontal Branch Stars

We report the identification of 23 faint blue horizontal branch stars in Omega Centauri similar to those discussed by Buonanno et al. (1985) in M15. We find that these stars are significantly concentrated towards the center of the cluster with respect to other giants. We suggest that they may have formed from the collision of a main sequence star and a white dwarf.

scholarly journals Detached white dwarf main-sequence star binaries

2004 ◽  
Vol 419 (3) ◽  
pp. 1057-1076 ◽  
Author(s):  
B. Willems ◽  
U. Kolb
Keyword(s):  
White Dwarf ◽  
Main Sequence ◽  
Main Sequence Star

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

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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