scholarly journals The X-ray Transient EXO 2030+375

1987 ◽  
Vol 125 ◽  
pp. 203-203
Author(s):  
A.N. Parmar ◽  
N.E. White ◽  
L. Stella ◽  
P. Ferri
Keyword(s):  
Orbital Period ◽  
Mass Function ◽  
Pulse Period ◽  
X Ray ◽  
Imaging Telescope ◽  
Be Star ◽  
X Ray Binaries

EXOSAT has observed a bright transient X-ray pulsar EXO 2030+375 that decayed in intensity by a factor ∼5000 between 1985 May and August. The variations in 42s pulse period enable an orbital period of 37.9±1.3 days with an eccentricity of 0.31±0.02 to be determined. The spin-up timescale of ∼30 years suggests that this is a very large outburst of order a few 1038 ergs/s. The mass function of 5Mo is consistent with the unidentified companion being a Be star, similar to many other pulsing X-ray binaries. The position of EXO 2030+375, obtained with the EXOSAT Imaging Telescope, is RA: 20 30 21.25, Decl. +37 27 51 (1950; with an uncertainty radius of 10″).

scholarly journals The frequency of Kozai–Lidov disc oscillation driven giant outbursts in Be/X-ray binaries

2019 ◽  
Vol 489 (2) ◽  
pp. 1797-1804 ◽  
Author(s):  
Rebecca G Martin ◽  
Alessia Franchini
Keyword(s):  
Orbital Period ◽  
Time Scale ◽  
Orbital Plane ◽  
Material Flows ◽  
X Ray ◽  
System Parameters ◽  
Be Star ◽  
Chaotic Nature ◽  
X Ray Binaries ◽  
Good Agreement

ABSTRACT Giant outbursts of Be/X-ray binaries may occur when a Be-star disc undergoes strong eccentricity growth due to the Kozai–Lidov (KL) mechanism. The KL effect acts on a disc that is highly inclined to the binary orbital plane provided that the disc aspect ratio is sufficiently small. The eccentric disc overflows its Roche lobe and material flows from the Be star disc over to the companion neutron star causing X-ray activity. With N-body simulations and steady state decretion disc models we explore system parameters for which a disc in the Be/X-ray binary 4U 0115+634 is KL unstable and the resulting time-scale for the oscillations. We find good agreement between predictions of the model and the observed giant outburst time-scale provided that the disc is not completely destroyed by the outburst. This allows the outer disc to be replenished between outbursts and a sufficiently short KL oscillation time-scale. An initially eccentric disc has a shorter KL oscillation time-scale compared to an initially circular orbit disc. We suggest that the chaotic nature of the outbursts is caused by the sensitivity of the mechanism to the distribution of material within the disc. The outbursts continue provided that the Be star supplies material that is sufficiently misaligned to the binary orbital plane. We generalize our results to Be/X-ray binaries with varying orbital period and find that if the Be star disc is flared, it is more likely to be unstable to KL oscillations in a smaller orbital period binary, in agreement with observations.

scholarly journals Be star disk structure as implied by X-ray observations

1994 ◽  
Vol 162 ◽  
pp. 213-215
Author(s):  
Priyamvada Saraswat ◽  
Krishna M.V. Apparao
Keyword(s):  
Orbital Period ◽  
Exact Nature ◽  
X Ray ◽  
Disk Structure ◽  
Be Star ◽  
Orbital Periods ◽  
X Ray Binaries

Compared to several other Be/X-ray binaries, 4U1907+09 has been observed more frequently due to the fact that it is found in an ‘on’ state more often. It also has a short orbital period of ~ 8 days as compared to the long orbital periods commonly found in these binaries. But despite the attention it has received, the exact nature of the primary remains elusive. While some observers maintain it to be a Be/X-ray binary, others prefer to put it into the class of OB supergiants.

scholarly journals Delimiting the black hole mass in the X-ray transient MAXI J1659-152 with Hα spectroscopy

2020 ◽  
Vol 501 (2) ◽  
pp. 2174-2181
Author(s):  
M A P Torres ◽  
P G Jonker ◽  
J Casares ◽  
J C A Miller-Jones ◽  
D Steeghs
Keyword(s):  
Black Hole ◽  
Orbital Period ◽  
Full Width Half Maximum ◽  
Compact Object ◽  
Mass Function ◽  
X Ray ◽  
Black Hole Candidate ◽  
Direct Irradiation ◽  
Hα Emission ◽  
X Ray Binaries

ABSTRACT MAXI J1659-152 is a 2.4 h orbital period X-ray dipping transient black hole candidate. We present spectroscopy of its I ≈ 23 quiescent counterpart, where we detect Hα emission with full width half maximum (FWHM) of 3200 ± 300 km s−1. Applying the correlation between the Hα FWHM and radial velocity semi-amplitude of the donor star for quiescent X-ray transients, we derive K2 = 750 ± 80 km s−1. The orbital period and K2 lead to a mass function of 4.4 ± 1.4 M⊙ (1σ). The donor to compact object mass ratio and binary inclination are likely in the range q = M2/M1 = 0.02–0.07 and i = 70○–80○. These constraints imply a 68 per cent confidence level interval for the compact object mass of 3.3 ≲ M1(M⊙) ≲ 7.5, confirming its black hole nature. These quasi-dynamical limits are compared to mass estimates from modelling of X-ray data and any discrepancies are discussed. We review the properties of optical spectroscopy and time-series photometry collected during the 2010–2011 outburst. We interpret the apparent modulations found soon after the onset of high-accretion activity and during the 2011 rebrightening event as originating in the accretion disc. These have signatures consistent with superhumps, with the 2011 modulation having a fractional period excess $\lt 0.6{\rm{per\, cent}}$ (3σ). We propose that direct irradiation of the donor by the central X-ray source was not possible due to its occultation by the disc outer regions. We argue that disc shielding significantly weakens the donor star contribution to the optical variability in systems with q ≲ 0.07, including neutron star ultra-compact X-ray binaries.

scholarly journals Search for intermittent X-ray pulsations from neutron stars in low-mass X-ray binaries

2021 ◽  
Vol 38 ◽  
Author(s):  
Yunus Emre Bahar ◽  
Manoneeta Chakraborty ◽  
Ersin Göğüş
Keyword(s):  
Neutron Stars ◽  
Orbital Period ◽  
Oscillation Frequency ◽  
Orbital Motion ◽  
X Rays ◽  
X Ray ◽  
Second Stage ◽  
Corrected Data ◽  
Low Mass ◽  
X Ray Binaries

Abstract We present the results of our extensive binary orbital motion corrected pulsation search for 13 low-mass X-ray binaries. These selected sources exhibit burst oscillations in X-rays with frequencies ranging from 45 to 1 122 Hz and have a binary orbital period varying from 2.1 to 18.9 h. We first determined episodes that contain weak pulsations around the burst oscillation frequency by searching all archival Rossi X-ray Timing Explorer data of these sources. Then, we applied Doppler corrections to these pulsation episodes to discard the smearing effect of the binary orbital motion and searched for recovered pulsations at the second stage. Here we report 75 pulsation episodes that contain weak but coherent pulsations around the burst oscillation frequency. Furthermore, we report eight new episodes that show relatively strong pulsations in the binary orbital motion corrected data.

scholarly journals The Relation between Spin and Orbital Periods in HMXBs

2003 ◽  
Vol 214 ◽  
pp. 215-217
Author(s):  
Q. Z. Liu ◽  
X. D. Li ◽  
D. M. Wei
Keyword(s):  
Magnetic Fields ◽  
Orbital Period ◽  
Critical Line ◽  
High Mass ◽  
Orbital Eccentricity ◽  
X Ray ◽  
Spin Period ◽  
Orbital Periods ◽  
X Ray Binaries

The relation between the spin period (Ps) and the orbital period (Po) in high-mass X-ray binaries (HMXBs) is investigated. In order for Be/X-ray binaries to locate above the critical line of observable X-ray emission due to accretion, it is necessary for an intermediate orbital eccentricity to be introduced. We suggest that some peculiar systems in the Po − Ps diagram are caused by their peculiar magnetic fields.

scholarly journals The Swift-BAT survey reveals the orbital period of three high-mass X-ray binaries

2011 ◽  
Vol 529 ◽  
pp. A30 ◽  
Author(s):  
A. D’Aì ◽  
V. La Parola ◽  
G. Cusumano ◽  
A. Segreto ◽  
P. Romano ◽  
...  
Keyword(s):  
Orbital Period ◽  
High Mass ◽  
X Ray ◽  
X Ray Binaries

scholarly journals X-ray binaries with neutron stars at different accretion stages

2018 ◽  
Vol 14 (S346) ◽  
pp. 219-227
Author(s):  
Konstantin A. Postnov ◽  
Alexander G. Kuranov ◽  
Lev R. Yungelson
Keyword(s):  
Magnetic Fields ◽  
Neutron Stars ◽  
Orbital Period ◽  
Population Synthesis ◽  
Circular Orbits ◽  
X Ray ◽  
Accretion Rates ◽  
Supercritical Accretion ◽  
Binary Evolution ◽  
X Ray Binaries

Abstract. Different accretion regimes onto magnetized NSs in HMXBs are considered: wind-fed supersonic (Bondi) regime at high accretion rates <math/> g s-1, subsonic settling regime at lower <math/> and supercritical disc accretion during Roche lobe overflow. In wind-fed stage, NSs in HMXBs reach equilibrium spin periods P* proportional to binary orbital period Pb. At supercritical accretion stage, the system may appear as a pulsating ULX. Population synthesis of Galactic HMXBs using standard assumptions on the binary evolution and NS formation is presented. Comparison of the model P* – Pb (the Corbet diagram), P* – Lx and Pb – Lx distributions with those for the observed HMXBs (including Be X-ray binaries) and pulsating ULXs suggests the importance of the reduction of P* in non-circular orbits, explaining the location of Be X-ray binaries in the model Corbet diagram, and the universal parameters of pulsating ULXs depending only on the NS magnetic fields.

scholarly journals Modelling decretion discs in Be/X-ray binaries

2019 ◽  
Author(s):  
R O Brown ◽  
M J Coe ◽  
W C G Ho ◽  
A T Okazaki
Keyword(s):  
Neutron Star ◽  
Orbital Period ◽  
Major Axis ◽  
High Mass ◽  
Model Parameters ◽  
Be Stars ◽  
Semi Major Axis ◽  
X Ray ◽  
Smoothed Particle ◽  
X Ray Binaries

Abstract As the largest population of high mass X-ray binaries, Be/X-ray binaries provide an excellent laboratory to investigate the extreme physics of neutron stars. It is generally accepted that Be stars possess a circumstellar disc, providing an additional source of accretion to the stellar winds present around young hot stars. Interaction between the neutron star and the disc is often the dominant accretion mechanism. A large amount of work has gone into modelling the properties of these circumstellar discs, allowing for the explanation of a number of observable phenomena. In this paper, smoothed particle hydroynamics simulations are performed whilst varying the model parameters (orbital period, eccentricity, the mass ejection rate of the Be star and the viscosity and orientation of the disc). The relationships between the model parameters and the disc’s characteristics (base gas density, the accretion rate of the neutron star and the disc’s size) are presented. The observational evidence for a dependency of the size of the Be star’s circumstellar disc on the orbital period (and semi-major axis) is supported by the simulations.

scholarly journals X-Ray Observations of B-Emission Stars (Review Paper)

1987 ◽  
Vol 92 ◽  
pp. 291-308 ◽  
Author(s):  
E.P.J. van den Heuvel ◽  
S. Rappaport
Keyword(s):  
Review Paper ◽  
Circumstellar Disks ◽  
Close Binaries ◽  
Be Stars ◽  
X Ray ◽  
Blue Stragglers ◽  
Galactic Clusters ◽  
Be Star ◽  
Emission Stars ◽  
X Ray Binaries

Most evidence on X-ray emission from the vicinity of Be stars concerns the Be/X-ray binaries. Presently some 20 of these systems are known, making them the most numerous class of massive X-ray binaries. Evidence for the binary nature of these systems comes from (i) Doppler modulation of X-ray pulse periods, (ii) periodic X-ray flaring behavior, and (iii) correlated optical and X-ray variability. The correlation between X-ray pulse period and orbital period found by Corbet (1984) can potentially provide important information on the densities and velocities in the circumstellar disks of Be stars.Evolutionary models indicate that the Be/X-ray binaries represent a later stage in the evolution of normal close binaries with initial primary masses predominantly in the the range 8 to 15 M⊙ . These models indicate that also a class of slightly less massive Be star binaries should exist in which the compact companions are white dwarfs. Be-type blue stragglers in galactic clusters may be such systems.

scholarly journals Observations and Evolutionary Scenario For Be/X-Ray Binaries

1987 ◽  
Vol 92 ◽  
pp. 509-513
Author(s):  
G.M.H.J. Habets
Keyword(s):  
Close Binaries ◽  
Disk Accretion ◽  
Primary Star ◽  
X Ray ◽  
Period Distribution ◽  
Evolutionary Scenario ◽  
M 10 ◽  
Be Star ◽  
Orbital Periods ◽  
X Ray Binaries

Rappaport & Van den Heuvel (1982) suggested the following formation scenario for B emission (Be)/X-ray binaries: the progenitor of the neutron star is the initial primary star with mass M1 = 10-20 M⊙, which during hydrogen-shell burning transfers mass to the companion (with M2 < M1). The secondary is spun up due to disk-accretion (e.g. Packet 1981) and has become a rapidly rotating Be star (M ≃ 10-20 M⊙).With this scenario the observed orbital periods (Porb > 15 d) of the Be/X-ray binaries can be explained. This was shown by van den Heuvel (1983) by adopting an idealized period distribution for unevolved O- and B-type close binaries with Porb, < 30 d (see Fig. 1) and assuming conservative evolution, i.e. that mass and angular momentum are conserved during mass transfer.

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