Stars In Binary Systems Research Articles

Be/neutron star binaries: Orbital and spin periods

The spin periods of accreting neutron stars in binary systems with Be star primaries are shown to depend more strongly on periastron distance than apastron distance. This is interpreted as showing that neutron stars spin-up on shorter timescales than they spin-down. The pulse and orbital periods of V 0332+53 suggest that the optical counterpart of this source is a Be star.

Infrared emission from accretion disks - Detectability and variability

view Abstract Citations (29) References (42) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Infrared emission from accretion disks : detectability and variability. Beall, J. H. ; Knight, F. K. ; Smith, H. A. ; Wood, K. S. ; Lebofsky, M. ; Rieke, G. Abstract The thermal spectrum of the infrared and optical emission from an accretion disk around a compact object has been calculated, assuming an optically thick, finite disk and a power-law dependence of disk temperature on radius. This calculated spectrum is then compared to the spectrum of blackbody radiators whose temperatures and radii are equivalent to B0 and O5 stars. For likely values of central disk temperature and maximum radius, the disk emission can dominate over the emitted spectrum of the companion star in a binary system. This occurs because the frequency dependence of the star's emission in the Rayleigh-Jeans limit (Sv is proportional to v-squared) falls off more rapidly with decreasing frequency than the emission from the disk. As illustrative examples, the consequences of these results for three black hole candidate systems (Cygnus X-1, Circinus X-1, and GX 339-4) are discussed. If not correctly understood the contribution of significant infrared and optical disk emission to the spectrum of the primary star can lead to serious errors in estimating the parameters of the binary system. Possible methods for determining the relative contributions from disk and star in binary systems are discussed. Publication: The Astrophysical Journal Pub Date: September 1984 DOI: 10.1086/162456 Bibcode: 1984ApJ...284..745B Keywords: Accretion Disks; Binary Stars; Infrared Astronomy; Stellar Mass Accretion; B Stars; Black Holes (Astronomy); Emission Spectra; O Stars; X Ray Sources; Astrophysics full text sources ADS | data products SIMBAD (3)

Discovery of a 7.1 hour period and eclipses from MXB 1659-29

A 7.1 hr period has been discovered in the X-ray emission from the 'transient' X-ray burst source MXB 1659-29. Erratic variations in X-ray flux are seen during approximately 25 percent of the 7.1 hr cycle; at the end of this period, a stable dip in the flux occurs. Further analysis indicates that this dip is, in all probability, an eclipse by the companion star in the low-mass binary system. The short (about 15 minute) eclipse duration is used to refine the period determination (7.114104 + or - 0.000168 hr) and to constrain the companion star mass and binary system parameters. The companion star is found to be in the range 0.25-0.9 solar mass; probabilistic arguments and observations of cataclysmic variables with comparable periods indicate that the companion star is most likely less massive than the standard theories would indicate.

Synchronization of magnetic stars in binary systems

Asynchronous rotation of magnetic stars in close binary systems drives substantial field-aligned electrical currents between the magnetic star and its companion. The resulting magnetohydrodynamic torque is able to account for the heretofore unexplained synchronous rotation of the strongly magnetic degenerate dwarf component in systems like AM Her, VV Pup, AN UMa, and EF Eri as well as the magnetic A type component in systems like HD 98088 and 41 Tauri. The electric fields produced by even a small asynchronism are large and may accelerate some electrons to high energies, producing radio emission. The total energy dissipation rate in systems with degenerate dwarf spin periods as short as 1 minute may reach 10 to the 33rd ergs/s. Total luminosities of this order may be a characteristic feature of such systems.

The evolution of a stripped giant-neutron star binary

view Abstract Citations (80) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The evolution of a stripped giant-neutron star binary. Taam, R. E. Abstract As a possible model for low-mass X-ray binaries in globular clusters and in the galactic bulge, the evolution of a stripped giant-neutron star binary system is investigated. The systems are characterized by masses less than 2.2 solar masses and periods greater than 0.766 days. It is found that mass transfer driven by nuclear evolution yields rates greater than or approximately equal to 10 to the -9th solar mass per yr for helium-core masses greater than or approximtely equal to 0.2 solar mass. The mass transfer rate varies slowly throughout until it abruptly ceases at the point when the stellar radius rapidly contracts from its critical Roche surface. The high mass transfer rates refect the more rapid stellar expansion associated with the giant in a more evolved state. Because the stellar radius is large in such models, the expected binary orbital periods are greater than or approximately equal to 1 day. Publication: The Astrophysical Journal Pub Date: July 1983 DOI: 10.1086/161160 Bibcode: 1983ApJ...270..694T Keywords: Binary Stars; Giant Stars; Neutron Stars; Stellar Evolution; X Ray Sources; Galactic Bulge; Globular Clusters; Hertzsprung-Russell Diagram; Stellar Mass Ejection; Stellar Models; X Ray Binaries; Astrophysics full text sources ADS | data products SIMBAD (2)

Diffusion, meridional circulation, and mass loss in Fm-Am stars

view Abstract Citations (159) References (39) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Diffusion, meridional circulation, and mass loss in Fm-Am stars Michaud, G. ; Tarasick, D. ; Charland, Y. ; Pelletier, C. Abstract The gravitational settling of helium is calculated in the presence of meridional circulation. The concentration of Fm-Am stars in binary systems with P between 2.5 and 100 days is then explained without any arbitrary parameter. Together with the other properties of Fm-Am stars that are explained without arbitrary parameter, this constitutes a strong argument in favor of the diffusion model for those objects. Calculations of helium settling and of the diffusion of heavy elements in the presence of mass loss are also carried out to show that a mass loss rate of 10 to the -15th - 10 to the -14th solar masses per yr is likely in Fm-Am stars. Some weak turbulence may subsist below the hydrogen convection zone. The effects of meridional circulation, mass loss, turbulence, and mixing length illustrate how the appearance of abundance anomalies is determined by the hydrodynamics of the outer stellar envelope. The Fm-Am stars offer an important contact between observations and hydrodynamical calculations. If the mass loss rate is about 10 to the -13th solar masses per yr, stars may spend more of their life as Lambda Bootis stars than as Fm-Am stars. Publication: The Astrophysical Journal Pub Date: June 1983 DOI: 10.1086/161034 Bibcode: 1983ApJ...269..239M Keywords: A Stars; Binary Stars; Metallic Stars; Peculiar Stars; Stellar Mass Ejection; Stellar Rotation; Abundance; Calcium; Gaseous Diffusion; Helium; Meridional Flow; Stellar Models; Astrophysics full text sources ADS |

Stellar contributions to the hard X-ray galactic ridge

The number density of serendipitous sources in galactic plane Einstein Observatory IPC fields are compared with predictions based on the intensity of the HEAO-1 A2 unresolved hrd X-ray galactic ridge emission. It is concluded that theoretically predicted X-ray source populations of luminosity 8 x 10 to the 32nd power to 3 x 10 to the 34th power ergs s have 2 KeV to 10 KeV local surface densities of less than approximately .0008 L(32) pc/2 and are unlikely to be the dominant contributors to the hard X-ray ridge. An estimate for Be/neutron star binary systems, such as X Persei, gives a 2 keV to 10 keV local surface density of approximately 26 x 10 to the -5 power L(32) pc/2. Stellar systems of low luminosity, are more likely contributors. Both RS CVn and cataclysmic variable systems contribute 43% + or - 18% of the ridge. A more sensitive measurement of the ridge's hard X-ray spectrum should reveal Fe-line emission. We speculate that dM stars are further major contributors.

Observations of New Wolf-Rayet Binaries

At present we know that the Wolf-Rayet stars do not form a homogeneous group of objects with similar masses, but that their masses span a considerable range. Whether or not there is a correlation between the masses and the different subtypes of WR stars, can only be answered by more observations of WR stars in binarysystems yielding estimates of the masses of their components.

Equilibrium figures for Beta Lyrae type disks

view Abstract Citations (23) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Equilibrium figures for BET LYR type disks. Wilson, R. E. Abstract Equilibrium figures for self-gravitating disks around stars in binary systems are computed, as a first step toward the computation of complete models for the geometrically and optically thick disk in the Beta Lyrae system with a well-defined photosphere. An important role is played by the centrifugally limited rotation of the central star, which would naturally arise late in the rapid phase of mass transfer, leading to the postulation of a double-contact binary structure which makes possible the nonarbitrary separation of star and disk into separate structures. The centrifugal potential is written in a form which permits the discontinuous changing of the rotation law while ensuring that centrifugal potential and force are continuous functions of position. Departures from axial symmetry resulting from the presence of the second star are illustrated, and the conditions which must be satisfied by a potential field are given. Publication: The Astrophysical Journal Pub Date: December 1981 DOI: 10.1086/159459 Bibcode: 1981ApJ...251..246W Keywords: Eclipsing Binary Stars; Photosphere; Stellar Gravitation; Stellar Mass Accretion; Stellar Models; Stellar Structure; Angular Velocity; Hydrodynamics; Mass Transfer; Potential Fields; Roche Limit; Stellar Rotation; Astrophysics full text sources ADS | data products SIMBAD (1)

Cyclotron absorption of x rays by a classical plasma in the strong magnetic fields of neutron stars

The cyclotron absorption of electromagnetic waves in an equilibrium classical plasma in a strong magnetic field is investigated on the basis of a kinetic equation and by means of Kirchhoff's law. A study is carried out of the influence of vacuum polarization by the magnetic field on the polarization of the ordinary and extraordinary waves and on the coefficients of cyclotron absorption of these waves in the plasma. The results obtained are of interest for the theory of the emission of X-ray sources associated with neutron stars in binary systems and above all for the theory of the origin of the X rays in the spectrum of the source Her X-1.

Neutron Stars in Binary Systems

Neutron Stars in Binary Systems

On the incidence of close binary stars in globular clusters and the nature of the cluster X-ray sources

{ '1§i7I~Ev'§€6I lie:-I Mon. Not. R. astr. Soc. (1977) 178, 335~343 On the incidence of close binary stars in globular clusters and the nature of the cluster X-ray sources Virginia * Department of Physics, University of California, Irvine, California 92 71 7, USA, and Astronomy Program, University of Maryland, College Park, Maryland 20 742, USA Received 1976 July 22; in original fonn 1976 May 17 Summary. Recent calculations by Hills suggest that the globular clusters could not have formed with more than 20 per cent of the normal Population I fraction of their stars in binary systems. The fact that the clusters have more than their fair share of novae and U Geminorum stars (three each out of ~ 200 of each known, while the clusters contain only about 10'“ of the mass and 10’3 of the luminosity of the galaxy) therefore becomes surprising. The hypo- thesis of binary capture within cluster cores suggested by Fabian, Pringle & Rees to account for the clusters’ high X-ray luminosity provides a few extra systems, but neither it nor any of the similar encounter or capture mechanisms suggested can account for the novae and U Gem stars, which remain puzzling. The numbers of Algol-type and WUMa eclipsing binaries predicted by these hypotheses do not conflict with data presently available, but careful searches for them would constitute a critical test of the theories. Background The identification of five strong, variable X-ray sources with the globular clusters NGC 1851, 6440, 6441, 6624 and 7078 (Giacconi et al. 1974; Clark, Markert & Li 1975; Markert et al. 1975) implies that the ratio of X-ray luminosity to optical luminosity (or mass) for the clusters is about 100 times that for our Galaxy as a whole (Katz 1975). The sorts of systems thought to be responsible for most galactic X-ray sources (neutron stars accreting matter supplied by normal companions in close binary systems) caxmot have survived in globular clusters from the time of their formation 10 billion or so years ago until the present (Clark 1975). Thus, some other mechanism is required. The clusters involved are richer and more centrally condensed (or, alternatively, have larger escape velocities and smaller core relaxation times) than typical globular clusters (Arp 1965; Kukarkin 1974; Peterson & King 1975), although not all rich, condensed clusters are X-ray sources (Uhner, Murray & Gursky 1976a). The mechanisms suggested have, there- fore, focused on processes that would be favoured by high stellar density and large escape * Alfred P. Sloan Foundation Research Fellow, 1972-74. © Royal Astronomical Society 0 Provided by the NASA Astrophysics Data System

Turbulence in Tidally Distorted Stars

view Abstract Citations (9) References (8) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Turbulence in Tidally Distorted Stars Seguin, Fredrick Hampton Abstract An investigation is made of the effects of tidal distortion on the stability of stars in binary systems against the development of turbulence and convection. Attention is limited to systems in which the stellar spin axis is perpendicular to the plane of the binary orbit. A short-wavelength linear stability analysis of an incompressible stellar model with laminar flow and tidally induced shear uncovers no instabilities. The analytic results of that analysis are supplemented by various heuristic considerations and used to argue in favor of the following statements: (i) Tidally induced shear, which has a special periodic, noncumulative nature, probably cannot cause turbulence through either dynamic or viscosity-induced linear instabilities. (ii) Tidal effects should not interfere with convection or turbulence which would be present in the absence of tidal distortion. (iii) It is not currently possible to decide whether or not tidally induced shear can cause turbulence through nonlinear instabilities. Subject headings: hydrodynamics - stars: binaries - turbulence Publication: The Astrophysical Journal Pub Date: August 1976 DOI: 10.1086/154555 Bibcode: 1976ApJ...207..848S full text sources ADS |

The absolute magnitudes of carbon stars - Carbon stars in binary systems

Absolute visual magnitudes have been determined for carbon stars belonging to binary systems. These range from about 0 to brighter than -4, with a mean value of -2.3 for N stars. Bolometric corrections are deduced, giving bolometric absolute magnitudes in the range -4 to -8.

On Angular Momentum Transfer in Binary Systems

The maximum limit for the conversion of orbital angular momentum into rotational angular momentum of the mass-gaining component in a close binary system is derived. It is shown that this conversion process does not seriously affect the rate of orbital period change and can be neglected in computing the mass transfer rate. Integration of this limit over the entire accretion process results in a value for the maximum accumulated rotational angular momentum that is 3 to 4 times larger than that implied by the observed underluminosity of stars in such systems as Mu(1) Sco, V Pup, SX Aur, and V356 Sgr. It is suggested that shell stars and emission-line stars in binary systems may be produced when the core angular momentum is transferred into an envelope having a rotational angular momentum close to the maximum limit.-

Infrared stars,in binary systems.

view Abstract Citations (65) References (27) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Infrared stars in binary systems. Humphreys, R. M. ; Ney, E. P. Abstract The peculiar A- and F-type supergiants, RD 101384, 89 Her, v Sgr, and R CrB have large and unusual infrared excesses which may be due to the presence of a very cool companion. In RD 101384 (F2e lap) more energy is radiated in the infrared than by the visible star. We suggest that the infrared energy is produced by an M supergiant companion instead of thermal reradiation by dust. RD 101384 also has a variable radial velocity with an amplitude of 20 km -i A P Cygni profile is observed at H and during two years the Ca ii H- and K-lines had more negative velocities by 30 km 1 from other lines. The stars 89 Her (F2e Ia) and v Sgr (cApe) show infrared excesses similar to RD 101384 which may also be produced by a very cool star. The peculiar carbon-rich star R CrB (F8pep) has an infrared excess closely resembling the Cygnid-type infrared objects. R CrB also has a regular light curve at 3.3 like the long-period variables. The infrared companion may be responsible in someway for this star's erratic behavior in the visual region. Sabject headings: binaries - infrared - luminous stars Publication: The Astrophysical Journal Pub Date: June 1974 DOI: 10.1086/152882 Bibcode: 1974ApJ...190..339H full text sources ADS | data products SIMBAD (16)

Soft X-Ray Variability of Binary X-Ray Stars

if X-ray stars in binary systems are neutron stars or black holes whose luminosity results from accretion from a stellar wind, they should have soft X-ray cutoffs in the observable range (0.25 keV < E < 5 keV) which vary in a predictable way according to the radius and inclination of the binary orbit. Subject headings: binaries - stellar winds - X-ray sources

Pulsar Observations and Neutron Star Models

Information about the physical parameters of neutron stars is obtained from pulsar observations. The energy balance of the Crab Nebula and the Vela X remnant allows one to derive limits for the masses of the Crab and Vela pulsars. Glitch observations provide further clues on the masses of these two pulsars. The degree of confidence with which one should believe the derived numbers is pointed out. The possibility of observing neutron stars in binary systems as pulsating X-ray sources is discussed. Finally, the importance of observing redshifted gamma ray lines from the surface of neutron stars, and thus directly measuring either individual or statistical properties of these objects, is pointed out.