scholarly journals The Evolutionary Status of PSR 1718–19

1996 ◽  
Vol 165 ◽  
pp. 73-79
Author(s):  
Ene Ergma ◽  
Marek J. Sarna
Keyword(s):  
Neutron Star ◽  
Binary System ◽  
Main Sequence ◽  
Roche Lobe ◽  
Evolutionary Status ◽  
Star Model ◽  
Eclipsing Binary ◽  
Matter Source

Possible models for the matter source inside the eclipsing binary system PSR 1718–19, and for the evolution of this system are reviewed, including Zwitter's (1993) stripped main-sequence (MS) turnoff star model. Both the accretion induced collapse (AIC) scenario with a young neutron star, and the capture scenario with an old neutron star are discussed. Although Burderi & King (1994) claim that the size of the Roche lobe (∼0.5 R⊙) unambiguously rules out the AIC formation scenario, we show that in our evolutionary picture an AIC scenario will be possible.

scholarly journals Eclipsing spotted giant star with K2 and historical photometry

2018 ◽  
Vol 620 ◽  
pp. A189 ◽  
Author(s):  
K. Oláh ◽  
S. Rappaport ◽  
T. Borkovits ◽  
T. Jacobs ◽  
D. Latham ◽  
...  
Keyword(s):  
Binary System ◽  
Main Sequence ◽  
Rapid Evolution ◽  
Magnetic Activity ◽  
Primary Component ◽  
Physical Parameters ◽  
Giant Star ◽  
Eclipsing Binary ◽  
Giant Stars ◽  
Active Stars

Context. Stars can maintain their observable magnetic activity from the pre-main sequence (PMS) to the tip of the red giant branch. However, the number of known active giants is much lower than active stars on the main sequence (MS) since the stars spend only about 10% of their MS lifetime on the giant branch. Due to their rapid evolution it is difficult to estimate the stellar parameters of giant stars. A possibility for obtaining more reliable stellar parameters for an active giant arises when it is a member of an eclipsing binary system. Aims. We have discovered EPIC 211759736, an active spotted giant star in an eclipsing binary system during the Kepler K2 Campaign 5. The eclipsing nature allows us to much better constrain the stellar parameters than in most cases of active giant stars. Methods. We have combined the K2 data with archival HATNet, ASAS, and DASCH photometry, new spectroscopic radial velocity measurements, and a set of follow-up ground-based BVRCIC photometric observations, to find the binary system parameters as well as robust spot models for the giant at two different epochs. Results. We determined the physical parameters of both stellar components and provide a description of the rotational and long-term activity of the primary component. The temperatures and luminosities of both components were examined in the context of the Hertzsprung–Russell diagram. We find that both the primary and the secondary components deviate from the evolutionary tracks corresponding to their masses in the sense that the stars appear in the diagram at lower masses than their true masses. Conclusions. We further evaluate the proposition that traditional methods generally result in higher masses for active giants than what is indicated by stellar evolution tracks in the HR diagram. A possible reason for this discrepancy could be a strong magnetic field, since we see greater differences in more active stars.

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.

scholarly journals WASP 0639-32: a new F-type subgiant/K-type main-sequence detached eclipsing binary from the WASP project

2018 ◽  
Vol 615 ◽  
pp. A135 ◽  
Author(s):  
J. A. Kirkby-Kent ◽  
P. F. L. Maxted ◽  
A. M. Serenelli ◽  
D. R. Anderson ◽  
C. Hellier ◽  
...  
Keyword(s):  
Binary System ◽  
Main Sequence ◽  
Mass Density ◽  
Helium Abundance ◽  
Eclipsing Binary ◽  
Abundance Estimate ◽  
Secondary Star ◽  
Free Parameters ◽  
Effective Temperatures ◽  
The Masses

Aims. Our aim is to measure the masses and radii of the stars in a newly-discovered detached eclipsing binary system to a high precision (≈1%), enabling the system to be used for the calibration of free parameters in stellar evolutionary models. Methods. Photometry from the Wide Angle Search for Planets (WASP) project was used to identify 1SWASP J063930.33-322404.8 (TYC 7091-888-1, WASP 0369-32 hereafter) as a detached eclipsing binary system with total eclipses and an orbital period of P = 11.66 days. Lightcurve parameters for WASP 0639-32 are obtained using the EBOP lightcurve model, with standard errors evaluated using a prayer-bead algorithm. Radial velocities were measured from 11 high-resolution spectra using a broadening function approach, and an orbit was fitted using SBOP. Observed spectra were disentangled and an equivalent width fitting method was used to obtain effective temperatures and metallicities for both stars. A Bayesian framework is used to explore a grid of stellar evolution models, where both helium abundance and mixing length are free to vary, and use observed parameters (mass, density, temperature, and metallicity) for each star to obtain the age and constrain the helium abundance of the system. Results. The masses and radii are found to be M1 = 1.1544 ± 0.0043 M⊙, R1 = 1.833 ± 0.023 R⊙, and M2 = 0.7833 ± 0.0028 M⊙, R2 = 0.7286 ± 0.0081 R⊙ for the primary and secondary, respectively. The effective temperatures were found to be T1 = 6330 ± 50 K and T2 = 5400 ± 80 K for the primary and secondary star, respectively. The system has an age of 4.2−0.1+0.8 Gyr, and a helium abundance in the range 0.251–0.271. Conclusions. WASP 0639-32 is a rare example of a well-characterised detached eclipsing binary system containing a star near the main-sequence turn-off point. This makes it possible to measure a precise age for the stars in this binary system and to estimate their helium abundance. Further work is needed to explore how this helium abundance estimate depends on other free parameters in the stellar models.

scholarly journals The Origin of Millisecond Pulsar Velocities

1996 ◽  
Vol 160 ◽  
pp. 51-52
Author(s):  
Thomas M. Tauris
Keyword(s):  
Neutron Star ◽  
Binary System ◽  
Orbital Period ◽  
Main Sequence ◽  
Space Velocity ◽  
Computer Code ◽  
Millisecond Pulsar ◽  
Final State ◽  
Pulsar Velocity ◽  
Orbital Periods

We have developed a computer code (Tauris & Bailes 1996) to follow the evolution of a binary system from the zero-age main sequence to its “final” state as a binary millisecond pulsar (BMSP), at all stages keeping careful track of the mass and orbital separation of the two stars.To help determine the origin of millisecond pulsars, we compute the space velocities predicted by various models of their formation. It is difficult to produce a millisecond pulsar velocity greater than 270 km s−1with any model, unless the formation of the neutron star is accompanied by some form of asymmetric kick. We obtain average 3-D system velocities of 〈vrecoil〉= 99.6, 137.6 and 160.7 km s−1using Gaussian kicks of 〈vkick〉=0, 200 and 450 km s−1(σ=0, 100 and 200 km s - 1, respectively). Our computations show that, in general, we expect those systems with shorter orbital periods to have larger velocities than those with longer periods, but any relation between the final orbital period and space velocity is fairly weak, especially if asymmetries are involved.

scholarly journals Disk Instabilities in Hubble-Sandage Variables?

1982 ◽  
Vol 69 ◽  
pp. 19-22
Author(s):  
F. Meyer ◽  
E. Meyer-Hofmeister
Keyword(s):  
Binary System ◽  
Color Index ◽  
Main Sequence ◽  
Roche Lobe ◽  
Main Sequence Star ◽  
Blue Color ◽  
High Luminosity ◽  
Wide Binary ◽  
Color Indices ◽  
Accretion Rates

The brightest individual objects in extragalactic nebulae are the Hubble-Sandage variables. They were first investigated by Hubble and Sandage (1953). Observations by Tamman and Sandage (1968) and Rosino and Bianchini (1973) followed. The main characteristics are high luminosity (L/Lʘ ≈ 105), blue color indices, F type spectra and irregular variability.Bath (1979) has suggested that the Hubble-Sandage variables contain an accreting main-sequence star with a Roche Lobe filling companion in a wide binary system. Based on this model we derive theoretical color indices for disks and determine the mass in the disk for different mass accretion rates. Further we discuss an instability of the disk which could explain the change in the color index observed for Var A in M33.

scholarly journals Orbital parameters and evolutionary status of the highly peculiar binary system HD 66051

2018 ◽  
Vol 615 ◽  
pp. A36 ◽  
Author(s):  
E. Paunzen ◽  
M. Fedurco ◽  
K. G. Hełminiak ◽  
O. I. Pintado ◽  
F.-J. Hambsch ◽  
...  
Keyword(s):  
Binary System ◽  
Spectroscopic Study ◽  
Main Sequence ◽  
Diffusion Theory ◽  
Photometric Data ◽  
Time Dependent ◽  
Evolutionary Status ◽  
Orbital Parameters ◽  
Spectroscopic Binary ◽  
Orbital Solution

Context. The spectroscopic binary system HD 66051 (V414 Pup) consists of a highly peculiar CP3 (HgMn) star and an A-type component. It also shows out-of-eclipse variability that is due to chemical spots. This combination allows the derivation of tight constraints for the testing of time-dependent diffusion models. Aims. We aim at deriving astrophysical parameters, information on age, and an orbital solution of the system. Methods. We analysed radial velocity and photometric data using two different methods to determine astrophysical parameters and the orbit of the system. Appropriate isochrones were used to derive the age of the system. Results. The orbital solution and the estimates from the isochrones are in excellent agreement with the estimates from a prior spectroscopic study. The system is very close to the zero-age main sequence and younger than 120 Myr. Conclusions. HD 66051 is a most important spectroscopic binary system that can be used to test the predictions of the diffusion theory explaining the peculiar surface abundances of CP3 stars.

scholarly journals FORMATION OF MILLISECOND PULSARS IN GLOBULAR CLUSTERS

1988 ◽  
Vol 03 (03) ◽  
pp. 229-235 ◽  
Author(s):  
ALAK RAY ◽  
AJIT KEMBHAVI
Keyword(s):  
Neutron Star ◽  
Binary System ◽  
Globular Clusters ◽  
Main Sequence ◽  
Orbital Energy ◽  
Mass Star ◽  
Tidal Dissipation ◽  
Period Derivative ◽  
Low Mass ◽  
The Individual

The low upper limit to the period derivative of the millisecond pulsar PSR 1821–24 occurring in the globular cluster M28 implies that it is not a part of any binary system. Various formation scenarios of such a pulsar, involving tidal capture of two stars into a gravitationally bound system, spin-up of the neutron star and disruption or unbinding of the companion star are considered in this letter. Of particular interest to these scenarios is the effect of tidal dissipation of orbital energy on the evolution of the individual stars and the binary system. We consider a scenario in which a massive white dwarf is captured tidally by a low mass star that has evolved off the main sequence, and later collapses to form a neutron star and eventually disrupts the degenerate helium core of the erstwhile companion due to unstable Roche-lobe overflow.

scholarly journals Collapse of Accreting White Dwarf to Form a Neutron Star

1979 ◽  
Vol 53 ◽  
pp. 56-60 ◽  
Author(s):  
Ken’ichi Nomoto ◽  
Shigeki Miyaji ◽  
Daiichiro Sugimoto ◽  
Koichi Yokoi
Keyword(s):  
Neutron Star ◽  
Binary System ◽  
Mass Exchange ◽  
White Dwarf ◽  
Mass Range ◽  
Close Binary System ◽  
Roche Lobe ◽  
Close Binary ◽  
Primary Star ◽  
Companion Star

AbstractIn a close binary system with a primary star in the mass range 8-12 M⊙, the primary star leaves a white dwarf composed of 16O, 20Ne, and 24Mg as a result of mass exchange. When the companion star, fills its Roche lobe, overflowing matter accretes onto the white dwarf. We have computed the evolution of such an accreting O-Ne-Mg white dwarf and found that electron captures on 24Mg and 20Ne trigger the collapse when the mass reaches 1.38 M⊙. As a result of the collapse, oxygen begins to deflagrate but the effects of electron captures dominate over the oxygen deflagration. The white dwarf collapses to form a neutron star.

scholarly journals The Dynamical Mass and Evolutionary Status of the Type II Cepheid in the Eclipsing Binary System OGLE-LMC-T2CEP-211 with a Double-ring Disk

2018 ◽  
Vol 868 (1) ◽  
pp. 30 ◽  
Author(s):  
Bogumił Pilecki ◽  
Ahmet Dervişoğlu ◽  
Wolfgang Gieren ◽  
Radosław Smolec ◽  
Igor Soszyński ◽  
...  
Keyword(s):  
Binary System ◽  
Evolutionary Status ◽  
Type Ii ◽  
Dynamical Mass ◽  
Eclipsing Binary ◽  
Double Ring
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