scholarly journals Unexpected Short-period Variability in Dwarf Carbon Stars from the Zwicky Transient Facility

2021 ◽  
Vol 922 (1) ◽  
pp. 33
Author(s):  
Benjamin R. Roulston ◽  
Paul J. Green ◽  
Silvia Toonen ◽  
J. J. Hermes
Keyword(s):  
Mass Transfer ◽  
Radial Velocity ◽  
Binary Systems ◽  
Roche Lobe ◽  
Light Curves ◽  
Common Envelope ◽  
Short Period ◽  
Velocity Variations ◽  
Rich Material

Abstract Dwarf carbon (dC) stars, main-sequence stars showing carbon molecular bands, are enriched by mass transfer from a previous asymptotic-giant-branch (AGB) companion, which has since evolved to a white dwarf. While previous studies have found radial-velocity variations for large samples of dCs, there are still relatively few dC orbital periods in the literature and no dC eclipsing binaries have yet been found. Here, we analyze photometric light curves from DR5 of the Zwicky Transient Facility for a sample of 944 dC stars. From these light curves, we identify 34 periodically variable dC stars. Remarkably, of the periodic dCs, 82% have periods less than two days. We also provide spectroscopic follow-up for four of these periodic systems, measuring radial velocity variations in three of them. Short-period dCs are almost certainly post-common-envelope binary systems, because the periodicity is most likely related to the orbital period, with tidally locked rotation and photometric modulation on the dC either from spots or from ellipsoidal variations. We discuss evolutionary scenarios that these binaries may have taken to accrete sufficient C-rich material while avoiding truncation of the thermally pulsing AGB phase needed to provide such material in the first place. We compare these dCs to common-envelope models to show that dC stars probably cannot accrete enough C-rich material during the common-envelope phase, suggesting another mechanism like wind-Roche lobe overflow is necessary. The periodic dCs in this paper represent a prime sample for spectroscopic follow-up and for comparison to future models of wind-Roche lobe overflow mass transfer.

scholarly journals Light Curves Analysis and Period Study of Two Eclipsing Binaries UZ Lyr and BR Cyg

2021 ◽  
Author(s):  
Kazem Yoosefi Roobiat ◽  
Reza Pazhouhesh
Keyword(s):  
Mass Transfer ◽  
Radial Velocity ◽  
Orbital Period ◽  
Binary Systems ◽  
Eclipsing Binaries ◽  
Light Curves ◽  
Secondary Component ◽  
Physical Parameters ◽  
Time Effects ◽  
First Time

Abstract Two eclipsing binary systems UZ Lyr and BR Cyg are the semi-detached types whose secondary component fill its Roche lobe. Although radial velocity and light curves of these systems have already been investigated separately, both radial velocity and light curves of them are analyzed simultaneously for the first time in the present study . Also, the orbital period changes of these systems are studied. Our results show that the mass transfer between components have negligible effects on the orbital period changes of these systems, but two light-time effects are the reasons of the periodic behavior of the O-C curve for UZ Lyr. We could not remark more information about orbital period changes for BR Cyg, but we find a new orbital period for it. By radial velocity and light curves analysis we find a clod spot on the secondary components of BR Cyg. The new geometrical and physical parameters of both systems are obtained and their positions on H-R diagram demonstrated.

Quasi-Periodic Oscillations in Dwarf Novae

1979 ◽  
Vol 46 ◽  
pp. 77-88
Author(s):  
Edward L. Robinson
Keyword(s):  
Binary Systems ◽  
Outer Edge ◽  
Light Curves ◽  
Close Binary ◽  
Bright Spot ◽  
Dwarf Novae ◽  
Periodic Oscillations ◽  
High Frequencies ◽  
Short Period ◽  
Typical Time

Three distinct kinds of rapid variations have been detected in the light curves of dwarf novae: rapid flickering, short period coherent oscillations, and quasi-periodic oscillations. The rapid flickering is seen in the light curves of most, if not all, dwarf novae, and is especially apparent during minimum light between eruptions. The flickering has a typical time scale of a few minutes or less and a typical amplitude of about .1 mag. The flickering is completely random and unpredictable; the power spectrum of flickering shows only a slow decrease from low to high frequencies. The observations of U Gem by Warner and Nather (1971) showed conclusively that most of the flickering is produced by variations in the luminosity of the bright spot near the outer edge of the accretion disk around the white dwarf in these close binary systems.

scholarly journals SuperWASP variable stars: classifying light curves using citizen science

2021 ◽  
Vol 502 (1) ◽  
pp. 1299-1311
Author(s):  
Heidi B Thiemann ◽  
Andrew J Norton ◽  
Hugh J Dickinson ◽  
Adam McMaster ◽  
Ulrich C Kolb
Keyword(s):  
Variable Stars ◽  
Eclipsing Binaries ◽  
Light Curves ◽  
Data Set ◽  
Resultant Data ◽  
Sky Survey ◽  
Short Period ◽  
Contact Binaries ◽  
Analysis Of Results

ABSTRACT We present the first analysis of results from the SuperWASP variable stars Zooniverse project, which is aiming to classify 1.6 million phase-folded light curves of candidate stellar variables observed by the SuperWASP all sky survey with periods detected in the SuperWASP periodicity catalogue. The resultant data set currently contains >1 million classifications corresponding to >500 000 object–period combinations, provided by citizen–scientist volunteers. Volunteer-classified light curves have ∼89 per cent accuracy for detached and semidetached eclipsing binaries, but only ∼9 per cent accuracy for rotationally modulated variables, based on known objects. We demonstrate that this Zooniverse project will be valuable for both population studies of individual variable types and the identification of stellar variables for follow-up. We present preliminary findings on various unique and extreme variables in this analysis, including long-period contact binaries and binaries near the short-period cut-off, and we identify 301 previously unknown binaries and pulsators. We are now in the process of developing a web portal to enable other researchers to access the outputs of the SuperWASP variable stars project.

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 The Formation of Compact Objects in Binary Systems

1981 ◽  
Vol 93 ◽  
pp. 155-175 ◽  
Author(s):  
E.P.J. van den Heuvel
Keyword(s):  
Mass Transfer ◽  
Binary Systems ◽  
Compact Star ◽  
Compact Objects ◽  
Binary Interaction ◽  
X Ray ◽  
Tidal Forces ◽  
Short Period ◽  
Wide Range ◽  
X Ray Binaries

The various ways in which compact objects (neutron stars and black holes) can be formed in interacting binary systems are qualitatively outlined on the basis of the three major modes of binary interaction identified by Webbink (1980). Massive interacting binary systems (M1 ≳ 10–12 M⊙) are, after the first phase of mass transfer expected to leave as remnants:(i) compact stars in massive binary systems (mass ≳ 10 M⊙) with a wide range of orbital periods, as remnants of quasi-conservative mass transfer; these systems later evolve into massive X-ray binaries.(ii) short-period compact star binaries (P ~ 1–2 days) in which the companion may be more massive or less massive than the compact object; these systems have high runaway velocities (≳ 100 km/sec) and start out with highly eccentric orbits, which are rapidly circularized by tidal forces; they may later evolve into low-mass X-ray binaries;(iii) single runaway compact objects with space velocities of ~ 102 to 4.102 km/sec; these are expected to be the most numerous compact remnants.Compact star binaries may also form from Cataclysmic binaries or wide binaries in which an O-Ne-Mg white dwarf is driven over the Chandrasekhar limit by accretion.

scholarly journals IUE Observations of the Two Peculiar Binary Systems Beta Lyrae and Upsilon Sagittarii

1980 ◽  
Vol 88 ◽  
pp. 271-286 ◽  
Author(s):  
Margherita Hack ◽  
Umberto Flora ◽  
Paolo Santin
Keyword(s):  
Mass Transfer ◽  
Mass Loss ◽  
Radial Velocity ◽  
Effective Temperature ◽  
Binary Systems ◽  
Close Binaries ◽  
Infrared Excess ◽  
Show Evidence ◽  
The Common ◽  
Ultraviolet Observations

The common peculiarities of these two systems are: a) the companion is a massive object (probably m2≥10) whose spectrum is not observable; b) both systems show evidence, though in different degrees, of mass-transfer and mass-loss; c) both present, in different degrees, hydrogen deficiency; d) ultraviolet observations have shown, in both cases, the presence of lines of highly ionized elements like N V, C IV, Si IV, probably formed in an extended envelope because they do not show orbital radial velocity shifts, and cannot be explained by the effective temperature of the star whose spectrum we observe. The latter property seems to be common to several close binaries, as shown by the ultraviolet observations with IUE by Plavec and Koch (1979); e) both systems present infrared excess, suggesting the presence of an extended envelope (Gehrz et al. 1974; Lee and Nariai, 1967; Humphreys and Ney, 1974; Treffers et al. 1976).

scholarly journals Wolf-Rayet binaries: old friends and new acquaintances

1999 ◽  
Vol 193 ◽  
pp. 26-37 ◽  
Author(s):  
Virpi S. Niemela ◽  
Roberto Gamen ◽  
Nidia I. Morrell ◽  
Sixto Giménez Benítez
Keyword(s):  
Radial Velocity ◽  
Binary Systems ◽  
Magellanic Cloud ◽  
Elliptic Orbit ◽  
Spectral Lines ◽  
Small Magellanic Cloud ◽  
Orbital Elements ◽  
Spectroscopic Observations ◽  
Short Period ◽  
Old Friends

Observations of WR stars in binary systems are discussed, emphasizing constraints on our knowledge of the binary frequency of WR stars, and of WR stars as a distinctive class of objects. Radial velocity orbits of newly discovered binaries, e.g., WR 29, a short period WN7+OB binary in our Galaxy, and SMC/AB 7, a massive WN+O7 binary in the Small Magellanic Cloud, are presented. New spectroscopic observations of binary systems with previously known orbits are also reported, showing in the case of WR 21 evidence of change of the orbital elements as derived from different spectral lines. An elliptic orbit for CV Ser is also illustrated.

scholarly journals Superoutbursts and Superhumps of SU UMa Stars

1988 ◽  
Vol 108 ◽  
pp. 238-239
Author(s):  
Yoji Osaki ◽  
Masahito Hirose
Keyword(s):  
Accretion Disk ◽  
Orbital Period ◽  
White Dwarf ◽  
Binary Systems ◽  
Roche Lobe ◽  
Light Curves ◽  
Close Binary ◽  
Dwarf Novae ◽  
Dwarf Nova ◽  
Close Binary Systems

SU UMa stars are one of subclasses of dwarf novae. Dwarf novae are semi-detached close binary systems in which a Roche-lobe filling red dwarf secondary loses matter and the white dwarf primary accretes it through the accretion disk. The main characteristics of SU UMa subclass is that they show two kinds of outbursts: normal outbursts and superoutbursts. In addition to the more frequent narrow outbursts of normal dwarf nova, SU UMa stars exhibit “superoutbursts”, in which stars reach about 1 magnitude brighter and stay longer than in normal outburst. Careful photometric studies during superoutburst have almost always revealed the “superhumps”: periodic humps in light curves with a period very close to the orbital period of the system. However, the most curious of all is that this superhump period is not exactly equal to the orbital period, but it is always longer by a few percent than the orbital period.

scholarly journals δ Sct-Type Pulsators in Eclipsing Binary Systems: the Case of RZ Cas

2002 ◽  
Vol 185 ◽  
pp. 102-103
Author(s):  
E. Rodríguez ◽  
V. Costa ◽  
M.J. López-González ◽  
J.M. García ◽  
S.L. Kim ◽  
...  
Keyword(s):  
Binary System ◽  
Binary Systems ◽  
Hot Spot ◽  
Primary Component ◽  
Roche Lobe ◽  
Light Curves ◽  
Eclipsing Binary ◽  
Preliminary Results ◽  
The Impact

AbstractRZ Cas is an Algol-type eclipsing binary system where the primary component was recently discovered as a δ Set pulsator. A three-continent multisite photometric campaign was carried out during 1999. Preliminary results are reported here indicating a semi-detached system where the secondary fills its Roche lobe. The light curves also suggest a hot spot on the surface of the primary component as a consequence of the impact of the mass stream from the secondary. The pulsational behaviour can be well described with only one frequency.

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