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 The White Dwarf Binary Pathways Survey – IV. Three close white dwarf binaries with G-type secondary stars

2020 ◽  
Vol 501 (2) ◽  
pp. 1677-1689
Author(s):  
M S Hernandez ◽  
M R Schreiber ◽  
S G Parsons ◽  
B T Gänsicke ◽  
F Lagos ◽  
...  
Keyword(s):  
Spectral Type ◽  
White Dwarf ◽  
Binary Stars ◽  
Cataclysmic Variable ◽  
Common Envelope ◽  
History Of ◽  
Low Mass ◽  
Orbital Periods ◽  
M Dwarf

ABSTRACT Constraints from surveys of post-common envelope binaries (PCEBs) consisting of a white dwarf plus an M-dwarf companion have led to significant progress in our understanding of the formation of close white dwarf binary stars with low-mass companions. The white dwarf binary pathways project aims at extending these previous surveys to larger secondary masses, i.e. secondary stars of spectral-type AFGK. Here, we present the discovery and observational characterization of three PCEBs with G-type secondary stars and orbital periods between 1.2 and 2.5 d. Using our own tools as well as MESA, we estimate the evolutionary history of the binary stars and predict their future. We find a large range of possible evolutionary histories for all three systems and identify no indications for differences in common envelope evolution compared to PCEBs with lower mass secondary stars. Despite their similarities in orbital period and secondary spectral type, we estimate that the future of the three systems is very different: TYC 4962-1205-1 is a progenitor of a cataclysmic variable system with an evolved donor star, TYC 4700-815-1 will run into dynamically unstable mass transfer that will cause the two stars to merge, and TYC 1380-957-1 may appear as supersoft source before becoming a rather typical cataclysmic variable star.

scholarly journals On Stothers’ and Simon’s Binary-Star Hypothesis for Beta Canis Majoris Star Pulsation

1971 ◽  
Vol 15 ◽  
pp. 197-203
Author(s):  
John R. Percy ◽  
Katherine Madore
Keyword(s):  
Mass Loss ◽  
Binary Systems ◽  
Main Sequence ◽  
Binary Star ◽  
Variable Stars ◽  
Pulsating Variable Stars ◽  
Short Period ◽  
Massive Binary Systems ◽  
Radial Pulsations ◽  
Rapid Mass

The β CMa stars are short-period pulsating variable stars lying slightly above the upper main sequence. Although they have been known and studied for 70 years, little is known about the nature and cause of their pulsation.STOTHERS and SIMON (1969) have recently advanced an hypothesis – hereinafter known as the hypothesis – which proposes that all β CMa stars are the former secondary components of massive binary systems. The former primary components, being more massive, have evolved first, have shed their envelopes by rapid mass loss, and have deposited helium-enriched material from their cores upon the surfaces of the secondary components. This causes the secondary components (now the primary components) to become unstable, via the so-called „μ-mechanism“, to nuclear-energized radial pulsations.

scholarly journals Binary evolution along the red giant branch with BINSTAR: The barium star perspective

2020 ◽  
Vol 639 ◽  
pp. A24 ◽  
Author(s):  
A. Escorza ◽  
L. Siess ◽  
H. Van Winckel ◽  
A. Jorissen
Keyword(s):  
White Dwarf ◽  
Binary Systems ◽  
Main Sequence ◽  
Asymptotic Giant Branch ◽  
Binary Interaction ◽  
Second Phase ◽  
Capture Process ◽  
Short Period ◽  
Binary Evolution ◽  
Red Giant

Barium (Ba), CH, and extrinsic or Tc-poor S-type stars are evolved low- and intermediate-mass stars that show enhancement of slow-neutron-capture-process elements on their surface, an indication of mass accretion from a former asymptotic giant branch companion, which is now a white dwarf (WD). Ba and CH stars can be found in the main-sequence (MS), the sub-giant, and the giant phase, while extrinsic S-type stars populate the giant branches only. As these polluted stars evolve, they might be involved in a second phase of interaction with their now white dwarf companion. In this paper, we consider systems composed of a main-sequence Ba star and a WD companion when the former evolves along the red giant branch (RGB). We want to determine if the orbital properties of the known population of Ba, CH, and S giants can be inferred from the evolution of their suspected dwarf progenitors. For this purpose, we used the BINSTAR binary evolution code and model MS+WD binary systems, considering different binary interaction mechanisms, such as a tidally enhanced wind mass loss, and a reduced circularisation efficiency. To explore their impact on the second RGB ascent, we compared the modelled orbits with the observed period and eccentricity distributions of Ba and related giants. We show that, independently of the considered mechanism, there is a strong period cut-off below which core-He burning stars should not be found in binary systems with a WD companion. This limit is shorter for more massive RGB stars and for more metal-poor systems. However, we still find a few low-mass short-period giant systems that are difficult to explain with our models, as well as two systems with very high eccentricities.

scholarly journals V392 Orionis: Observations and Evolutionary State of a Low-Mass System

1998 ◽  
Vol 11 (1) ◽  
pp. 371-371
Author(s):  
S. Narusawa ◽  
A. Yamasaki ◽  
Y. Nakamura
Keyword(s):  
Binary Systems ◽  
Main Sequence ◽  
Circumstellar Matter ◽  
Small Mass ◽  
Primary Component ◽  
Close Binary ◽  
Mass System ◽  
Future Evolution ◽  
Short Period ◽  
Low Mass

Although the evolution of binary systems has been qualitatively interpreted with the evolutionary scenario, the quantitative interpretation of any observed system is still unsatisfactory due to the difficulty of the quantitative treatment of mass and angular momentum transfer/loss. To reach a true understanding of the evolution of binary systems, we have to accumulate more observational evidence. So far, we have observed several binaries that are short-period and noncontact, and found the existence of extremely small-mass systems. In the present paper, we study another short-period (P=0.659d), noncontact, eclipsing binary system, V392 Ori. We have made photometric and spectroscopic observations of V392 Ori. The light curves are found to vary, suggesting the existence of circumstellar matter around the system. Combining the photometric and spectroscopic results, we obtain parameters describing the system; we find the mass of the primary component is only 0.6Mʘ- undermassive for its spectral and luminosity class A5V, suggesting that a considerable amount of its original mass has been lost from the system during the course of evolution. The low-mass problem is very important for investigation of the evolution of close binary systems: largemass loss within and/or after the main-sequence will have a significant influence on the future evolution of binary systems.

scholarly journals Two-dimensional simulations of mixing in classical novae: The effect of white dwarf composition and mass

2018 ◽  
Vol 619 ◽  
pp. A121 ◽  
Author(s):  
Jordi Casanova ◽  
Jordi José ◽  
Steven N. Shore
Keyword(s):  
White Dwarf ◽  
Binary Systems ◽  
Main Sequence ◽  
Chemical Species ◽  
Two Dimensions ◽  
Classical Novae ◽  
Nova Shells ◽  
Solar Abundances ◽  
Low Mass ◽  
Thermonuclear Runaway

Context. Classical novae are explosive phenomena that take place in stellar binary systems. They are powered by mass transfer from a low-mass main sequence star onto either a CO or ONe white dwarf. The material accumulates for 104–105 yr until ignition under degenerate conditions, resulting in a thermonuclear runaway. The nuclear energy released produces peak temperatures of ∼0.1–0.4 GK. During these events, 10−7−10−3 M⊙ enriched in intermediate-mass elements, with respect to solar abundances, are ejected into the interstellar medium. However, the origin of the large metallicity enhancements and the inhomogeneous distribution of chemical species observed in high-resolution spectra of ejected nova shells is not fully understood. Aims. Recent multidimensional simulations have demonstrated that Kelvin-Helmholtz instabilities that operate at the core-envelope interface can naturally produce self-enrichment of the accreted envelope with material from the underlying white dwarf at levels that agree with observations. However, such multidimensional simulations have been performed for a small number of cases and much of the parameter space remains unexplored. Methods. We investigated the dredge-up, driven by Kelvin-Helmholtz instabilities, for white dwarf masses in the range 0.8–1.25 M⊙ and different core compositions, that is, CO-rich and ONe-rich substrates. We present a set of five numerical simulations performed in two dimensions aimed at analyzing the possible impact of the white dwarf mass, and composition, on the metallicity enhancement and explosion characteristics. Results. At the time we stop the simulations, we observe greater mixing (∼30% higher when measured in the same conditions) and more energetic outbursts for ONe-rich substrates than for CO-rich substrates and more massive white dwarfs.

Radial Velocity Variations in Cool Supergiants

1984 ◽  
Vol 88 ◽  
pp. 283-288
Author(s):  
Hugh C. Harris
Keyword(s):  
Radial Velocity ◽  
Main Sequence ◽  
Short Period ◽  
Cool Stars ◽  
Synchronous Rotation ◽  
Red Supergiants ◽  
Velocity Variations ◽  
Orbital Periods ◽  
Low Amplitude ◽  
Good Agreement

AbstractA survey of F, G, and W supergiants has been carried out with the DAO radial velocity spectrometer, an efficient instrument for detecting low-amplitude velocity variations in cool stars. Observations of 78 stars over five seasons show generally good agreement with OORAVEL results for spectroscopie binaries. The majority of supergiants show low-amplitude variability, with amplitudes typically 1 to 2 km s−1. The width of the cross-correlation profile has been measured for 58 supergiants. It reveals 14 stars with unusually broad lines, indicative of rotation velocities of 15 to 35 km s−1. Several have short-period binary companions and may be in synchronous rotation. The other broad-lined stars are apparently single or with long orbital periods; they may be making their first transition from the main sequence to become red supergiants.

scholarly journals Classical Novae – Before and After Outburst

1988 ◽  
Vol 108 ◽  
pp. 226-231
Author(s):  
Mario Livio
Keyword(s):  
White Dwarf ◽  
Main Sequence ◽  
Orbital Parameters ◽  
Classical Novae ◽  
Classical Nova ◽  
Before And After ◽  
Low Mass ◽  
Orbital Periods ◽  
Thermonuclear Runaway ◽  
Nova Outburst

Classical nova (CN) and dwarf nova (DN) systems have the same binary components (a low-mass main sequence star and a white dwarf) and the same orbital periods. An important question that therefore arises is: are these systems really different ? (and if so, what is the fundamental difference ?) or, are these the same systems, metamorphosing from one class to the other ?The first thing to note in this respect is that the white dwarfs in DN systems are believed to accrete continuously (both at quiescence and during eruptions). At the same time, both analytic (e.g. Fujimoto 1982) and numerical calculations show, that when sufficient mass accumulates on the white dwarf, a thermonuclear runaway (TNR) is obtained and a nova outburst ensues (see e.g. reviews by Gallagher and Starrfield 1978, Truran 1982). It is thus only natural, to ask the question, is the fact that we have not seen a DN undergo a CN outburst (in about 50 years of almost complete coverage) consistent with observations of DN systems ? In an attempt to answer this question, we have calculated the probability for a nova outburst not to occur (in 50 years) in 86 DN systems (for which at least some of the orbital parameters are known).

scholarly journals Progress of Common Envelope Evolution

1989 ◽  
Vol 8 ◽  
pp. 155-159
Author(s):  
R. E. Taam
Keyword(s):  
Binary System ◽  
Time Scale ◽  
Binary Systems ◽  
Efficiency Factor ◽  
Final Phase ◽  
Common Envelope ◽  
Orbital Decay ◽  
Mass Outflow ◽  
The Common ◽  
Orbital Periods

AbstractThe current understanding of the common envelope binary phase of evolution is presented. The results obtained from the detailed computations of the hydrodynamical evolution of this phase demonstrate that the deposition of energy by the double core via frictional processes is sufficiently rapid to drive a mass outflow, primarily in the equatorial plane of the binary system. Specifically, recent calculations suggest that large amounts of mass and angular momentum can be lost from the binary system in a such a phase. Since the time scale for mass loss at the final phase of evolution is much shorter than the orbital decay time scale of the companion, the tranformation of binary systems from long orbital periods (> month) to short orbital periods (< day) is likely. The energy efficiency factor for the process is estimated to lie in the range between 0.3 and 0.6.

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 Eclipse timing variation of GK Vir: evidence of a possible Jupiter-like planet in a circumbinary orbit

2020 ◽  
Vol 497 (3) ◽  
pp. 4022-4029
Author(s):  
L A Almeida ◽  
E S Pereira ◽  
G M Borges ◽  
A Damineli ◽  
T A Michtchenko ◽  
...  
Keyword(s):  
Orbital Period ◽  
Binary Systems ◽  
Orbital Stability ◽  
Theoretical Description ◽  
Apsidal Motion ◽  
Variation Analysis ◽  
Third Body ◽  
Common Envelope ◽  
Cyclic Behaviour ◽  
Orbital Periods

ABSTRACT Eclipse timing variation analysis has become a powerful method to discover planets around binary systems. We applied this technique to investigate the eclipse times of GK Vir. This system is a post-common envelope binary with an orbital period of 8.26 h. Here, we present 10 new eclipse times obtained between 2013 and 2020. We calculated the O−C diagram using a linear ephemeris and verified a clear orbital period variation (OPV) with a cyclic behaviour. We investigated if this variation could be explained by the Applegate mechanism, the apsidal motion, or the light travel time (LTT) effect. We found that the Applegate mechanism would hardly explain the OPV with its current theoretical description. We obtained using different approaches that the apsidal motion is a less likely explanation than the LTT effect. We showed that the LTT effect with one circumbinary body is the most likely cause for the OPV, which was reinforced by the orbital stability of the third body. The LTT best solution provided an orbital period of ∼24 yr for the outer body. Under the assumption of coplanarity between the external body and the inner binary, we obtained a Jupiter-like planet around the GK Vir. In this scenario, the planet has one of the longest orbital periods, with a full observational baseline, discovered so far. However, as the observational baseline of GK Vir is smaller than twice the period found in the O−C diagram, the LTT solution must be taken as preliminary.

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