Time-Resolved Spectroscopy of Short Period RS CVn Systems

AbstractWe have initiated a programme of spectroscopic observations of RS CVn short-period group, with orbital phase resolution. The systems of this group are all eclipsing binaries with both components at the Main Sequence, and most of them have similar spectral type components. The high rotational velocities and their short orbital periods (less than 1 day) hinder the spectroscopic study of these stars. We presents the first results yielded by Hα line observations of the systems XY UMa and WY Cnc. Both systems were observed during 1991 with reasonably wide orbital phase coverage. The analysis of the spectra is made by comparison with a binary model, constructed from the observed spectra of normal stars of the same spectral type as the RS CVn system components. The model accounts for the partial contribution of each component at any orbital phase within eclipses.

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Radial Velocity Variations in Cool Supergiants

International Astronomical Union Colloquium ◽

10.1017/s0252921100098900 ◽

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.

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A survey for high-mass eclipsing binaries

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2953 ◽

2019 ◽

Vol 490 (4) ◽

pp. 5147-5173

Author(s):

F Pozo Nuñez ◽

R Chini ◽

A Barr Domínguez ◽

Ch Fein ◽

M Hackstein ◽

...

Keyword(s):

Eclipsing Binaries ◽

Light Curves ◽

High Mass ◽

System Component ◽

Fundamental Parameters ◽

Average Value ◽

Short Period ◽

Orbital Periods ◽

Photometric Monitoring ◽

Period System

ABSTRACT We report results from a search for Galactic high-mass eclipsing binaries. The photometric monitoring campaign was performed in Sloan r and i with the robotic twin refractor RoBoTT at the Universitätssternwarte Bochum in Chile and complemented by Johnson UBV data. Comparison with the SIMBAD data base reveals 260 variable high-mass stars. Based on well-sampled light curves, we discovered 35 new eclipsing high-mass systems and confirm the properties of six previously known systems. For all objects, we provide the first light curves and determine orbital periods through the Lafler–Kinman algorithm. Apart from GSC 08173-0018 and Pismis 24-13 ($P = 19.47\, d$ and $20.14\, d$) and the exceptional short-period system TYC 6561-1765-1 ($P = 0.71\, d$), all systems have orbital periods between 1 and 9 d. We model the light curves of 26 systems within the framework of the Roche geometry and calculate fundamental parameters for each system component. The Roche lobe analysis indicates that 14 systems have a detached geometry, while 12 systems have a semidetached geometry; seven of them are near-contact systems. The deduced mass ratios q = M2/M1 reach from 0.4 to 1.0 with an average value of 0.8. The similarity of masses suggests that these high-mass binaries were created during the star formation process rather than by tidal capture.

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Differential rotation in convective envelopes: constraints from eclipsing binaries

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2983 ◽

2019 ◽

Vol 491 (1) ◽

pp. 690-707 ◽

Cited By ~ 1

Author(s):

Adam S Jermyn ◽

Jamie Tayar ◽

Jim Fuller

Keyword(s):

Differential Rotation ◽

Orbital Period ◽

Binary Systems ◽

Rotation Period ◽

Eclipsing Binaries ◽

Rotation Periods ◽

Short Period ◽

Orbital Periods ◽

The Difference ◽

Surface Convection

ABSTRACT Over time, tides synchronize the rotation periods of stars in a binary system to the orbital period. However, if the star exhibits differential rotation, then only a portion of it can rotate at the orbital period, so the rotation period at the surface may not match the orbital period. The difference between the rotation and orbital periods can therefore be used to infer the extent of the differential rotation. We use a simple parametrization of differential rotation in stars with convective envelopes in circular orbits to predict the difference between the surface rotation period and the orbital period. Comparing this parametrization to observed eclipsing binary systems, we find that in the surface convection zones of stars in short-period binaries there is very little radial differential rotation, with |r∂rln Ω| < 0.02. This holds even for longer orbital periods, though it is harder to say which systems are synchronized at long periods, and larger differential rotation is degenerate with asynchronous rotation.

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Modelling Kepler eclipsing binaries: homogeneous inference of orbital and stellar properties

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2137 ◽

2019 ◽

Vol 489 (2) ◽

pp. 1644-1666 ◽

Cited By ~ 4

Author(s):

D Windemuth ◽

E Agol ◽

A Ali ◽

F Kiefer

Keyword(s):

Main Sequence ◽

Spectral Energy Distribution ◽

Eclipsing Binaries ◽

Spectral Energy ◽

Parameter Estimates ◽

Kepler Mission ◽

Short Period ◽

Show Evidence ◽

Stellar Properties ◽

Stellar Masses

Abstract We report on the properties of eclipsing binaries (EBs) from the Kepler mission with a newly developed photometric modelling code, which uses the light curve, spectral energy distribution of each binary, and stellar evolution models to infer stellar masses without the need for radial velocity (RV) measurements. We present solutions and posteriors to orbital and stellar parameters for 728 systems, forming the largest homogeneous catalogue of full Kepler binary parameter estimates to date. Using comparisons to published RV measurements, we demonstrate that the inferred properties (e.g. masses) are reliable for well-detached main-sequence (MS) binaries, which make up the majority of our sample. The fidelity of our inferred parameters degrades for a subset of systems not well described by input isochrones, such as short-period binaries that have undergone interactions, or binaries with post-MS components. Additionally, we identify 35 new systems which show evidence of eclipse timing variations, perhaps from apsidal motion due to binary tides or tertiary companions. We plan to subsequently use these models to search for and constrain the presence of circumbinary planets in Kepler EB systems.

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Spectroscopy of WZ Sagittae

International Astronomical Union Colloquium ◽

10.1017/s0252921100075849 ◽

1979 ◽

Vol 53 ◽

pp. 139-139

Author(s):

C.C. Brunt ◽

J.A.J. Whelan

Keyword(s):

Photon Counting ◽

Line Profiles ◽

S Wave ◽

Time Resolved ◽

Broad Absorption Line ◽

Before And After ◽

Orbital Phase ◽

Orbital Periods ◽

Set Up

WZ Sge was observed spectroscopically during quiescence in August 1978 and July 1979, before and after the December 1978 outburst. The same instrumental set up was used, namely the Image Photon Counting System on the Anglo-Australian Telescope. Time resolved spectra were obtained in phase over several orbital periods, in wavelength ranges covering Hβ and Hγ and also separately Hα. These data are being used to study the “before and after” changes in the emission line profiles, in the radial velocities of the S-wave and of the emission lines, and in the broad absorption line profiles. Additionally these features are being studied as a function of orbital phase in order to improve the determination of system parameters. When completed, the results will be published elsewhere.

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The Rotation of the Main-Sequence Components of Algol-Type Semi-Detached Eclipsing Binaries

International Astronomical Union Colloquium ◽

10.1017/s0252921100027172 ◽

1970 ◽

Vol 4 ◽

pp. 178-186

Author(s):

E.P.J. Van Den Heuvel

Keyword(s):

Spectral Type ◽

Spectral Region ◽

Main Sequence ◽

Rotational Velocity ◽

Eclipsing Binaries ◽

Main Sequence Stars ◽

Sequence Components ◽

Tentative Explanation ◽

Region Ii ◽

Existing Data

AbstractNewly determined rotational velocities of the main-sequence components of 14 Algol-type semi-detached systems and of 2 detached systems are presented. Combination of these data with the existing data on the rotation of the components of semi-detached systems shows that (i) in systems with primaries of spectral type B8 or later and with P<5 days, deviations from synchronism between rotation and revolution are small in 14 out of 15 cases. The average rotational velocity of the primaries in such systems is 75 km/sec, viz. only 40% of the average rotational velocity of single main-sequence stars in the same spectral region: (ii) primaries of spectral type earlier than B8 in systems with short as well as long periods tend to rotate more than twice as fast as one would expect from synchronism. A tentative explanation for these results is presented.

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On the Origin of the Algol Systems

Highlights of Astronomy ◽

10.1017/s1539299600001544 ◽

1968 ◽

Vol 1 ◽

pp. 396-408

Author(s):

M. Plavec

Keyword(s):

Spectral Type ◽

Main Sequence ◽

Eclipsing Binaries ◽

List Type ◽

Type Number ◽

Main Sequence Stars ◽

Maximum Light ◽

Spectral Class ◽

Lagrangian Surfaces ◽

Visual Binaries

The 4th edition of the Finding List for Observers of Eclipsing Variables (Koch et al, 1963) contains 145 sufficiently well-observed eclipsing binaries brighter than 8·5m at maximum light. Among them, 59 binaries, or 41%, are systems with both components on the main sequence. The second largest group, 52 binaries or 36% of all systems, are systems similar to Algol. These can be characterized as follows: (1)The primary (more massive) components are main-sequence stars, fitting well into the mass-luminosity relation defined by visual binaries and by eclipsing binaries with both components on the main sequence (detached systems).(2)The secondary components are of later spectral type than the primaries, and can be best characterized as subgiants. They are overluminous for their mass as well as for their spectral class.(3)As a rule, the secondary components fill their respective critical Roche lobes (innermost Lagrangian surfaces).

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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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Physical Properties of 29 sdB+dM Eclipsing Binaries in Zwicky Transient Facility

Research in Astronomy and Astrophysics ◽

10.1088/1674-4527/ac49e5 ◽

2022 ◽

Author(s):

Min Dai ◽

Xiaodian Chen ◽

Kun WANG ◽

Yangping Luo ◽

Shu Wang ◽

...

Keyword(s):

Physical Properties ◽

Large Scale ◽

Probability Distributions ◽

Brown Dwarfs ◽

Eclipsing Binaries ◽

Mass Ratio ◽

Light Curve Analysis ◽

Short Period ◽

Orbital Periods ◽

The Masses

Abstract The development of large-scale time-domain surveys provides an opportunity to study the physical properties as well as the evolutionary scenario of B-type subdwarfs (sdB) and M-type dwarfs (dM). Here, we obtained 33 sdB+dM eclipsing binaries based on the Zwicky Transient Facility (ZTF) light curves and {\sl Gaia} early data release 3 (EDR3) parallaxes. By using the PHOEBE code for light curve analysis, we obtain probability distributions for parameters of 29 sdB+dM. $R_1$, $R_2$, and $i$ are well determined, and the average uncertainty of mass ratio $q$ is 0.08. Our parameters are in good agreement with previous works if a typical mass of sdB is assumed. Based on parameters of 29 sdB+dM, we find that both the mass ratio $q$ and the companion's radius $R_2$ decrease with the shortening of the orbital period. For the three sdB+dMs with orbital periods less than 0.075 days, their companions are all brown dwarfs. The masses and radii of the companions satisfy the mass--radius relation for low-mass stars and brown dwarfs. Companions with radii between $0.12R_\odot$ and $0.15R_\odot$ seem to be missing in the observations. As more short-period sdB+dM eclipsing binaries are discovered and classified in the future with ZTF and {\sl Gaia}, we will have more information to constrain the evolutionary ending of sdB+dM.

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A Limit on the Space Density of Short-Period Binary White Dwarfs

International Astronomical Union Colloquium ◽

10.1017/s0252921100100132 ◽

1989 ◽

Vol 114 ◽

pp. 492-497

Author(s):

Edward L. Robinson ◽

Allen W. Shafter

Keyword(s):

Orbital Period ◽

Binary Stars ◽

White Dwarfs ◽

Main Sequence ◽

Close Binaries ◽

Main Sequence Stars ◽

Space Density ◽

Short Period ◽

Hot Subdwarfs ◽

Orbital Periods

We infer that detached binary white dwarfs with orbital periods of a few hours exist because we observe both their progenitors and their descendents. The binary LB 3459 has an orbital period of 6.3 hr and contains a pair of hot subdwarfs that will eventually cool to become white dwarfs (Kilkenny, Hill, and Penfold 1981). L870-2 is a pair of white dwarfs and, given enough time, its 1.55 d orbital period will decay to shorter periods (Saffer, Liebert, and Olszewski 1988). GP Com, AM CVn, V803 Cen, and PG1346+082 are interacting binary white dwarfs with orbital periods between 1051 s for AM CVn and 46.5 min for GP Com (Nather, Robinson, and Stover 1981; Solheim et al. 1984; Wood et al. 1987; O’Donoghue and Kilkenny 1988). These ultrashort period systems must be descendents of detached pairs of white dwarfs. We also expect short-period binary white dwarfs to exist for theoretical reasons. All calculations of the evolution of binary stars show that main-sequence binaries can evolve to binary white dwarfs (e.g., Iben and Tutukov 1984). Among Population I stars, 1/2 to 2/3 of all main-sequence stars are binaries and about 20% of these binaries should become double white dwarfs with short orbital periods (Abt 1983, Iben and Tutukov 1986). Thus, about 1/10 of all white dwarfs could be close binaries (Paczynski 1985). Nevertheless, no detached binary white dwarfs with extremely short periods have yet been found.

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