scholarly journals Optical Counterparts to Be/X-ray Binaries in the Magellanic Clouds

1999 ◽  
Vol 192 ◽  
pp. 112-115
Author(s):  
David A. H. Buckley ◽  
James B. Stevens ◽  
Malcolm J. Coe
Keyword(s):  
Neutron Star ◽  
Magellanic Clouds ◽  
Optical Identification ◽  
Ccd Photometry ◽  
X Ray ◽  
Transient Nature ◽  
Be Star ◽  
Hα Emission ◽  
Early Type Stars ◽  
X Ray Binaries

We discuss the optical identification of 9 Be/X-ray binary optical counterparts of X-ray sources in the Magellanic clouds, most of them discovered in ROSAT observations. Imaging CCD photometry (using BV RC and Hα filters) was employed to search the typically 20 arcsec radius error circles for early-type stars exhibiting Hα emission. Spectroscopy of 5 candidates confirmed the presence of Hα emission. Based on the positional coincidences, we propose Be star optical counterparts to all of 9 X-ray sources: 6 from ROSAT and one each from ASCA, EXOSAT and HEAO-1. All of the sources exhibit the typical X-ray characteristics of Be/neutron star X-ray binaries: transient nature or strong variability, relatively hard X-ray spectra and, in 5 cases, detections of probable neutron star spin periods in the range 8.9 to 91.1 seconds.

scholarly journals Be/X-Ray Binaries with Black Holes in the Galaxy and in the Magellanic Clouds

2014 ◽  
Vol 1 (1) ◽  
pp. 175-180 ◽  
Author(s):  
Janusz Ziolkowski
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Neutron Star ◽  
Magellanic Clouds ◽  
X Ray ◽  
The Galaxy ◽  
X Ray Binaries ◽  
Successful Candidate

I will start with the statistics indicating that the objects named in the title of my talk are either non-existing or very elusive to detect (not a single such object is known against 119 known Be/neutron star X-ray binaries). After brief reviewing of the properties of Be/X-ray binaries I discuss several objects that were proposed as the long sought for candidates for Be/black hole X-ray binaries. After three unsuccessful candidates (LS I +61° 303, LS 5039 and MAXI J1836-194), a successful candidate (AGL J2241+4454/MWC 656) was finally, very recently, announced.

scholarly journals On the apparent lack of Be X-ray binaries with black holes in the galaxy and in the Magellanic Clouds

2010 ◽  
Vol 6 (S275) ◽  
pp. 329-330
Author(s):  
Janusz Ziółkowski ◽  
Krzysztof Belczyński
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Neutron Star ◽  
Stellar Population ◽  
Magellanic Clouds ◽  
Population Synthesis ◽  
X Ray ◽  
Stellar Population Synthesis ◽  
The Galaxy ◽  
X Ray Binaries

AbstractIn the Galaxy there are 67 Be X-ray binaries known to-date. Out of those, 45 host a neutron star, and for the reminder the nature of a companion is not known. None, so far, is known to host a black hole. This disparity is referred to as a missing Be – black hole X-ray binary problem. The stellar population synthesis calculations following the formation of Be X-ray binaries (Belczyński & Ziółkowski 2009) predict that the ratio of the binaries with neutron stars to the ones with black holes is rather high FNS/BH ~ 30–50. A comparison of this ratio with the number of confirmed Be – neutron star X-ray binaries (45) indicates that the expected number of Be – black hole X-ray binaries is of the order of only ~0–2. This is entirely consistent with the observed Galactic sample. Therefore, there is no problem of the missing Be+BH X-Ray Binaries for the GalaxyIn the Magellanic Clouds there are 94 Be X-ray binaries known to-date. Out of those, 60 host a neutron star. Again, none hosts a black hole. The stellar population synthesis calculations carried out specifically for the Magellanic Clouds (Ziółkowski & Belczyński 2010) predict that the ratio of the Be X-ray binaries with neutron stars to the ones with black holes is only FNS/BH ~ 10. This value is rather too low, as it implies the expected number of Be+BH X-ray binaries of the order of ~6, while none is observed. We found, that to remove the discrepancy, one has to take into account a different history of the star formation rate in the Magellanic Clouds, with the respect to the Galaxy. New stellar population synthesis calculations are currently being carried out.

scholarly journals Multiwavelength observations of the Be-star/X-ray binary EXO2030+375 during outburst

1994 ◽  
Vol 162 ◽  
pp. 206-207
Author(s):  
A.J. Norton ◽  
M.J. Coe ◽  
C. Everall ◽  
P. Roche ◽  
L. Bildsten ◽  
...  
Keyword(s):  
Neutron Star ◽  
Emission Lines ◽  
Be Stars ◽  
Infrared Excess ◽  
X Ray ◽  
Circumstellar Material ◽  
Spin Period ◽  
Be Star ◽  
Star Surface ◽  
X Ray Binaries

EXO2030+375 consists of a neutron star in an eccentric 46 day orbit around a 20th magnitude Be-star companion (Coe et al., 1988; Parmar et al., 1989; Stollberg et al., 1993). The Be-star is thought to be surrounded by a shell/disc of material which is responsible for the infrared excess and Balmer emission lines which are characteristic of Be-stars in general. At periastron, the neutron star passes through this circumstellar material, giving rise to enhanced accretion onto the neutron star surface. As a result of this, the X-ray emission (pulsed at the neutron star spin period of 41.8s) increases dramatically, so producing the transient, outburst behaviour which is commonly seen in Be-star / X-ray binaries.

scholarly journals Eccentric Neutron Star Disk Driven Type II Outburst Pairs in Be/X-ray Binaries

2021 ◽  
Vol 923 (1) ◽  
pp. L18
Author(s):  
Alessia Franchini ◽  
Rebecca G. Martin
Keyword(s):  
Mass Transfer ◽  
Neutron Star ◽  
Type I ◽  
Type Ii ◽  
X Ray ◽  
Be Star ◽  
Orbital Periods ◽  
Hydrodynamical Simulations ◽  
X Ray Binaries ◽  
Lower Luminosity

Abstract Be star X-ray binaries are transient systems that show two different types of outbursts. Type I outbursts occur each orbital period while type II outbursts have a period and duration that are not related to any periodicity of the binary system. Type II outbursts may be caused by mass transfer to the neutron star from a highly eccentric Be star disk. A sufficiently misaligned Be star decretion disk undergoes secular Von Zeipel–Lidov–Kozai (ZLK) oscillations of eccentricity and inclination. Observations show that in some systems the type II outbursts come in pairs with the second being of lower luminosity. We use numerical hydrodynamical simulations to explore the dynamics of the highly misaligned disk that forms around the neutron star as a consequence of mass transfer from the Be star disk. We show that the neutron star disk may also be ZLK unstable and that the eccentricity growth leads to an enhancement in the accretion rate onto the neutron star that lasts for several orbital periods, resembling a type II outburst. We suggest that in a type II outburst pair, the first outburst is caused by mass transfer from the eccentric Be star disk while the second and smaller outburst is caused by the eccentric neutron star disk. We find that the timescale between outbursts in a pair may be compatible with the observed estimates.

scholarly journals Properties of X-ray binaries in the Magellanic Clouds from RXTE and Chandra observations

2008 ◽  
Vol 4 (S256) ◽  
pp. 361-366 ◽  
Author(s):  
R. H. D. Corbet ◽  
M. J. Coe ◽  
K. E. McGowan ◽  
M. P. E. Schurch ◽  
L. J. Townsend ◽  
...  
Keyword(s):  
Neutron Star ◽  
Milky Way ◽  
Magellanic Clouds ◽  
Light Curves ◽  
X Ray ◽  
Timing Information ◽  
Monitoring Programs ◽  
Extended Duration ◽  
X Ray Binaries

AbstractThe X-ray binary population of the SMC is very different from that of the Milky Way consisting, with one exception, entirely of transient pulsating Be/neutron star binaries. We have now been monitoring these SMC X-ray pulsars for over 10 years using the Rossi X-ray Timing Explorer with observations typically every week. The RXTE observations have been complemented with surveys made using the Chandra observatory. The RXTE observations are non-imaging but enable detailed studies of pulsing sources. In contrast, Chandra observations can provide precise source locations and detections of sources at lower flux levels, but do not provide the same timing information or the extended duration light curves that RXTE observations do. We summarize the results of these monitoring programs which provide insights into both the differences between the SMC and the Milky Way, and the details of the accretion processes in X-ray pulsars.

scholarly journals Mass-Capture Rate by the Neutron Star in Be/X-Ray Binaries

2004 ◽  
Vol 194 ◽  
pp. 144-145
Author(s):  
A. T. Okazaki ◽  
K. Hayasaki
Keyword(s):  
Neutron Star ◽  
Capture Rate ◽  
Three Dimensional ◽  
Orbital Plane ◽  
Orbital Eccentricity ◽  
X Ray ◽  
Mass Capture ◽  
Be Star ◽  
X Ray Binaries

AbstractWe study the interaction between the Be-star disk and the neutron star in Be/X-ray binaries by three dimensional SPH simulations. We find that, the resonant, truncation of the Be disk works except for systems with extremely high orbital eccentricity or large misalignment angles between the Be disk and the orbital plane. Owing to the truncation, the mass-capture rate by the neutron star is sensitive both to the orbital eccentricity and to the angle of misalignment. It is single-peaked in coplanar systems and in systems with small misalignment angles, whereas it, becomes double-peaked in systems with large misalignment angles.

scholarly journals Accretion Onto the Neutron Star in Be/X-ray Binaries

2004 ◽  
Vol 218 ◽  
pp. 449-450
Author(s):  
Kimitake Hayasaki ◽  
Atsuo T. Okazaki
Keyword(s):  
Neutron Star ◽  
High Resolution ◽  
Accretion Disk ◽  
Time Dependent ◽  
Disk Model ◽  
X Ray ◽  
Short Period ◽  
Be Star ◽  
X Ray Binaries ◽  
Resolution Simulation

We study accretion onto the neutron star in Be/X-ray binaries, using a 3D SPH code and the data imported from a high resolution simulation by Okazaki et al. (2002) for a coplanar system with a short period (Porb = 24.3 d) and moderate eccentricity (e = 0.34). We find that a time-dependent accretion disk is formed around the neutron star in Be/X-ray binaries. The disk shrinks after the periastron passage of the Be star and restores its radius afterwards. Our simulations show that the truncated Be disk model for Be/X-ray binaries is consistent with the observed X-ray behavior.

On the nature of the X-ray outbursts in Be/X-ray binaries

2018 ◽  
Vol 14 (S346) ◽  
pp. 146-148
Author(s):  
Jingzhi Yan ◽  
Wei Liu ◽  
Peng Zhang ◽  
Qingzhong Liu
Keyword(s):  
Neutron Star ◽  
Compact Object ◽  
Optical Emission ◽  
Light Curves ◽  
High Mass ◽  
Circumstellar Disk ◽  
X Ray ◽  
Be Star ◽  
The Relationship ◽  
X Ray Binaries

AbstractBe/X-ray binaries are a major subclass of high mass X-ray binaries. Two different X-ray outbursts are displayed in the X-ray light curves of such systems. It is generally believed that the X-ray outbursts are connected with the neutron star periastron passage of the circumstellar disk around the Be star. The optical emission of the Be star should be very important to understand the X-ray emission of the compact object. We have monitored several Be/X-ray binaries photometrically and spectroscopically in the optical band. The relationship between the optical emission and X-ray activity is described, which is very useful to explain the X-ray outbursts in Be/X-ray binaries.

scholarly journals Multi-wavelength Study of the Be/X-ray Binaries

2012 ◽  
Vol 8 (S290) ◽  
pp. 351-352
Author(s):  
J. Z. Yan ◽  
H. Li ◽  
J. N. Zhou ◽  
Q. Z. Liu
Keyword(s):  
Circumstellar Disk ◽  
Density Region ◽  
X Ray ◽  
Multi Wavelength ◽  
Be Star ◽  
Hα Emission ◽  
Optical Brightness ◽  
Mass Ejection ◽  
X Ray Binaries ◽  
Ejection Event

AbstractAn anti-correlation between the optical brightness and the strength of the Hα emission was observed from two Be/X-ray binaries, A0535+26 and MXB 0656-072: when the optical brightness showed a decrease, the intensity of the Hα emission displayed an obvious increase. This anti-correlation is interpreted as the result of the mass ejection from the Be star. After the mass ejection event, a cavity or low-density region will be developing in the inner parter of the circumstellar disk. The X-ray outbursts of the Be/X-ray binaries might be connected with the mass ejections from the Be star.

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