scholarly journals Stagnation-point flow in colliding-wind binary systems

1995 ◽  
Vol 163 ◽  
pp. 522-522
Author(s):  
Ian R. Stevens ◽  
Andrew M.T. Pollock
Keyword(s):  
Radiation Field ◽  
Binary Systems ◽  
Mass Loss Rate ◽  
Terminal Velocity ◽  
Close Binary ◽  
Single Star ◽  
Lower Velocity ◽  
X Ray ◽  
Radiation Fields ◽  
Star Models

The low X-ray temperatures and luminosities of colliding wind binaries compared to theoretical expectations has been a long standing problem. As a potential solution to this problem we present quantitative calculations of the radiation hydrodynamics in colliding wind binary systems, accounting for the effect of two radiation fields on the dynamics of both winds, using a formulation similar to that of Castor et al. (1975, ApJ 195, 157). A more detailed description of this work can be found in Stevens & Pollock (1994, MNRAS in press). Consider only the WR wind being driven under the influence of the WR and O-star radiation fields and motion only on the line-of-centers. Near the WR-star, its own radiation field dominates, and the mass-loss rate will be largely unaffected by the presence of the companion. However, moving towards the O-star, the O-star radiation field becomes a significant fraction of the total flux. As the O-star radiation field is opposed to the WR radiation field the radiative line-force will be diminished and the wind acceleration diminished. This will lead to the WR star wind colliding with the O-star wind at a lower velocity than would be expected from single star models. This mechanism will only be at work in close binary systems. In wide binaries both winds will be at terminal velocity before the other radiation field makes a difference. Results for a sample calculation are shown in Fig 1, using parameters for V444 Cyg from Schmutz et al. (1989, A&A 210, 236). In the absence of any deceleration effects the WR wind velocity at the shock would be ∼ 1300 km s−1, corresponding to kT ∼ 2 keV. The reduction in the WR star velocity at the shock interface caused by the O-star radiation field is predicted to be ∼ x2 leading to kTx ∼ 0.5 keV, in line with X-ray observations.

scholarly journals Glimpses of Be Binary Evolution

2000 ◽  
Vol 175 ◽  
pp. 668-680 ◽  
Author(s):  
Douglas R. Gies
Keyword(s):  
Neutron Stars ◽  
Binary Systems ◽  
Rotational Velocity ◽  
Close Binary ◽  
Be Stars ◽  
Star System ◽  
Single Star ◽  
X Ray ◽  
Binary Evolution ◽  
X Ray Binaries

AbstractModels of close binary evolution predict that mass gainers will be spun up to speeds close to the critical rotational velocity while the mass donors will appear as stripped down He stars, white dwarfs, or neutron stars. I argue here that the mass gainers are closely related to the Be stars. I present a list of the known Be binary systems which consists of those with bright, Roche-filling companions and those with faint or undetected companions. Notably absent are Be + B systems which are expected if the Be phase is a stage in the life of a single star. We now have the first example of a Be + He star system in the binary, ϕ Per, and taken together with the well known Be X-ray binaries, there is clear evidence that some fraction of Be stars are created in binaries; whether all such rapid rotators are so formed remains unknown.

scholarly journals Rotation and Massive Close Binary Evolution

2007 ◽  
Vol 3 (S250) ◽  
pp. 167-178 ◽  
Author(s):  
Norbert Langer ◽  
Matteo Cantiello ◽  
Sung-Chul Yoon ◽  
Ian Hunter ◽  
Ines Brott ◽  
...  
Keyword(s):  
Binary Systems ◽  
Close Binary ◽  
Single Star ◽  
Essential Ingredient ◽  
Critical Rotation ◽  
Close Binary Systems ◽  
Star Models ◽  
Binary Evolution ◽  
Massive Close Binary

AbstractWe review the role of rotation in massive close binary systems. Rotation has been advocated as an essential ingredient in massive single star models. However, rotation clearly is most important in massive binaries where one star accretes matter from a close companion, as the resulting spin-up drives the accretor towards critical rotation. Here, we explore our understanding of this process, and its observable consequences. When accounting for these consequences, the question remains whether rotational effects in massive single stars are still needed to explain the observations.

scholarly journals X-ray and UV emission of the ultrashort-period, low-mass eclipsing binary system BX Trianguli

2018 ◽  
Vol 619 ◽  
pp. A138
Author(s):  
V. Perdelwitz ◽  
S. Czesla ◽  
J. Robrade ◽  
T. Pribulla ◽  
J. H. M. M. Schmitt
Keyword(s):  
Binary System ◽  
Light Curve ◽  
Binary Systems ◽  
Uv Light ◽  
Close Binary ◽  
Eclipsing Binary ◽  
X Ray ◽  
Uv Emission ◽  
Low Mass ◽  
Orbital Modulation

Context.Close binary systems provide an excellent tool for determining stellar parameters such as radii and masses with a high degree of precision. Due to the high rotational velocities, most of these systems exhibit strong signs of magnetic activity, postulated to be the underlying reason for radius inflation in many of the components. Aims.We extend the sample of low-mass binary systems with well-known X-ray properties. Methods.We analyze data from a singular XMM-Newton pointing of the close, low-mass eclipsing binary system BX Tri. The UV light curve was modeled with the eclipsing binary modeling tool PHOEBE and data acquired with the EPIC cameras was analyzed to search for hints of orbital modulation. Results.We find clear evidence of orbital modulation in the UV light curve and show that PHOEBE is fully capable of modeling data within this wavelength range. Comparison to a theoretical flux prediction based on PHOENIX models shows that the majority of UV emission is of photospheric origin. While the X-ray light curve does exhibit strong variations, the signal-to-noise ratio of the observation is insufficient for a clear detection of signs of orbital modulation. There is evidence of a Neupert-like correlation between UV and X-ray data.

scholarly journals X-Ray Sources in Close Binary Systems

1974 ◽  
Vol 3 ◽  
pp. 89-107
Author(s):  
M. J. Rees
Keyword(s):  
Binary Systems ◽  
Close Binary ◽  
Rapid Variability ◽  
X Ray ◽  
Close Binary Systems ◽  
General Order ◽  
Typical Distances ◽  
Astronomical Research ◽  
Orbital Periods ◽  
Galactic Sources

The discovery by Giacconi and his colleagues of variable X-ray sources in close binary systems certainly ranks as one of the highlights of astronomical research during the last 3 years. These remarkable objects have already been extensively studied, by optical and radio observations as well as in the X-ray band; and they seem likely to prove as significant and far-reaching in their implications as pulsars.The ‘Third Uhuru Catalogue’ (Giacconi et al., 1973a) contains about 160 sources, of which about 100 lie in our Galaxy. Their distribution over the sky (together with other arguments) suggests that these sources have luminosities of the general order 1036–1038 erg s−1, and that their typical distances are ˜ 10kpc. These galactic sources generally display rapid variability. Little else is known about most of them, but they are probably of the same general class as systems such as Her X1, Cen X3, Cyg X1 and Cyg X3. These sources have been investigated in detail, and in all cases one infers a system where the X-ray source is orbiting around a relatively ordinary star. Six sources have been optically identified, and there are some others whose binary nature is established by the occurrence of an X-ray eclipse. Orbital periods range from 4.8 h (Cyg X3) up to ˜ 10 days.

scholarly journals Radio Aspects of Stellar Activity in Close Binaries

1980 ◽  
Vol 5 ◽  
pp. 857-857 ◽  
Author(s):  
R. M. Hjellming
Keyword(s):  
Circular Polarization ◽  
Binary Systems ◽  
Close Binary ◽  
Close Binaries ◽  
Radiation Mechanisms ◽  
Dynamo Action ◽  
Stellar Activity ◽  
X Ray ◽  
Close Binary Systems ◽  
Decay Times

Excluding single stars, star systems with very strong X-ray sources, thermally radiating winds and circumstellar envelopes, marginal detections, and binary systems that are far from “normal”, there are about 21 close binary systems that show clear signs of stellar activity in the form of variable radio emission. Sixteen of these are RS CVn binaries. Typical events are smoothly varying with time scales of from a few hours to a few days. In the RS CVn binaries UX Ari and V711 Tau variable circular polarization is sometimes observed, with occasional appearence of components with only one frequency and one circular polarization, part of which shows “oscillations” with “periods” of about 4 minutes. Different stars and different events typically have inferred electron energies of about 5 MeV and inferred magnetic fields of 1 - 30 Gauss. The radiation mechanisms are usually assumed to be synchrotron or gyro-synchrotron; however, radiation from plasma processes cannot be ruled out in some cases, and it will be very important to establish or rule out this possibility. Most radio binary events show clear signs of self-absorption, so the variations appear most strongly at the higher frequencies. Typical rise times of events are about 30% of decay times. Maximum radio luminosities range from 1013 to a few times 1017 ergs s-1 Hz-1. Most radio flares are mainly at cm-wavelenghts and have observable and inferred energies 104 - 106 times those for the largest solar events, a scaling which is similar to that for X-ray emission measures of these stars when compared to solar coronal loop emission measures. Most importantly, VLBI measurements of Algol indicate that the sizes of the radio emitting regions for very strong events are of the order of 2 - 3 stellar radii. Single stars appear to be active at radio wavelengths much less commonly than close binary systems. In many cases this may be due to the way dynamo action and convection near the surface are affected by increased rotation forced by the synchronization induced by the binary system.

scholarly journals THE 3-D NUMERICAL SIMULATIONS OF THE DEPENDENCE OF THE DISK STRUCTURE FROM THE WIND CONFIGURATION IN ONE-POINT IN MICROQUASAR CYG X-1. THE CASE OF THE HIGH RESOLUTION GRID IN THE VERTICAL DIRECTION

2021 ◽  
Vol 34 ◽  
pp. 56-58
Author(s):  
V.V. Nazarenko
Keyword(s):  
Accretion Disk ◽  
Binary Systems ◽  
Mass Loss Rate ◽  
Vertical Direction ◽  
The Other ◽  
High Mass ◽  
Close Binary ◽  
Standard Size ◽  
Disk Radius ◽  
Disk Structure

The present paper is devoted to the investigation how the disk structure is depending from the one-point wind one in microquasar CYG X-1. The results show that when the region in which the wind is absent in the vicinity of one-point has the size less or equal to 0.07 the disk radius is very small, order of 0.08 in units of orbital separation. When this size is increased to 0.115 the disk radius becomes to be of standard size to be equal to 0.22 in units of orbital separation. By the other words these results show that the disk structure is strong depending from many factors including and the donor’s wind configuration in the vicinity of one-point. This configuration is inherent to microquasars only. Indeed, since microqausars are the massive close binary systems; the donor in these systems is massive star from which the strong radiation- driving wind is blowing. On the other hand, in microquasars accretion disks are present and it means that one-point stream is also present in microqausars. It in turn means that the matter configuration in the vicinity of one-point is very complicated since the high mass loss rate donor’s wind and one-point stream must be existing in the vicinity of one-point simultaneously. This situation maybe resolved when we suppose that the central source in an accretion disk will influence on the donor’s atmosphere structure in the vicinity of  one-point and in turn will be result in the break of wind in the vicinity of one-point. This finally will be means that one-point stream will be existing in one-point without a wind and it, flowing in the accretor’s Roche lobe, will be result in an accretion disk forma- tion. Here one problem is arising: what is the configuration of wind in the extended vicinity of one-point  and from what the parameters this configuration is depending and haw this configuration will be results to the disk structure change. We good understand that this situation is arising in the case of microquasars only and we try to resolve this problem in the present paper.

scholarly journals Explosions of Helium Stars and Type IB/IC/IIB Supernovae

1991 ◽  
Vol 143 ◽  
pp. 515-528 ◽  
Author(s):  
K. Nomoto
Keyword(s):  
Binary Systems ◽  
Theoretical Models ◽  
Light Curves ◽  
Close Binary ◽  
Star Models ◽  
Helium Stars ◽  
Fast Decline ◽  
Supernova Explosions ◽  
Low Mass ◽  
Helium Star

Theoretical models of supernova explosions of helium stars with various masses are reviewed to examine possible connections between Wolf-Rayet stars and Type Ib/Ic/IIb supernovae. Nucleosynthesis, Rayleigh-Taylor instabilities, and light curves are compared with observations. Maximum brightness and the fast decline of the light curves of typical SNe Ib/Ic can be well accounted for by the helium star models if the helium star mass is as low as 3-5 M⊙. These low mass helium stars can form from stars of 12-18 M⊙ after Roche-lobe overflow in close binary systems. Probably progenitors of typical SNe Ib/Ic are not classified as Wolf-Rayet stars.

scholarly journals Structures of Binary Star Coronae

2004 ◽  
Vol 219 ◽  
pp. 199-210
Author(s):  
Nancy S. Brickhouse
Keyword(s):  
Binary Systems ◽  
Binary Star ◽  
Magnetic Loop ◽  
Close Binaries ◽  
Coronal Emission ◽  
Single Star ◽  
X Ray ◽  
Radio Studies ◽  
Show Evidence ◽  
Contact Binaries

Stellar coronae in binary star systems offer both a puzzle and an opportunity. We might expect that large magnetic loop structures on close binaries, such as RS CVn systems and contact binaries, would show evidence for interactions between the stars. While some radio studies support this scenario, there is surprisingly little evidence from EUV and X-ray observations for differences between binary and single star systems. Meanwhile, the binary systems offer observational opportunities through rotational modulation and eclipses of flaring and non-flaring regions. Localizing the sources of coronal emission is key to making the magnetic connection to the underlying photosphere. We discuss the structure of stellar coronae from the perspective of studies of binary systems.

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