scholarly journals NGC 300 ULX1: A new ULX pulsar in NGC 300

2018 ◽  
Vol 14 (S346) ◽  
pp. 242-246 ◽  
Author(s):  
Chandreyee Maitra ◽  
Stefania Carpano ◽  
Frank Haberl ◽  
Georgios Vasilopoulos
Keyword(s):  
Neutron Star ◽  
Power Law ◽  
Accretion Rate ◽  
Black Body ◽  
High Mass ◽  
X Ray ◽  
Body Model ◽  
X Ray Binaries ◽  
Intrinsic Luminosity

Abstract. NGC 300 ULX1 is the fourth to be discovered in the class of the ultra-luminous X-ray pulsars. Pulsations from NGC 300 ULX1 were discovered during simultaneous XMM-Newton / NuSTAR observations in Dec. 2016. The period decreased from 31.71 s to 31.54 s within a few days, with a spin-up rate of –5.56×10–7 s s–1, likely one of the largest ever observed from an accreting neutron star. Archival Swift and NICER observations revealed that the period decreased exponentially from ~45 s to ~17.5 s over 2.3 years. The pulses are highly modulated with a pulsed fraction strongly increasing with energy and reaching nearly 80% at energies above 10 keV. The X-ray spectrum is described by a power-law and a disk black-body model, leading to a 0.3–30 keV unabsorbed luminosity of 4.7×1039 erg s–1. The spectrum from an archival XMM-Newton observation of 2010 can be explained by the same model, however, with much higher absorption. This suggests, that the intrinsic luminosity did not change much since that epoch. NGC 300 ULX1 shares many properties with supergiant high mass X-ray binaries, however, at an extreme accretion rate.

scholarly journals Mass transfer on a nuclear timescale in models of supergiant and ultra-luminous X-ray binaries

2019 ◽  
Vol 628 ◽  
pp. A19 ◽  
Author(s):  
M. Quast ◽  
N. Langer ◽  
T. M. Tauris
Keyword(s):  
Mass Transfer ◽  
Black Hole ◽  
Neutron Star ◽  
Roche Lobe ◽  
High Mass ◽  
X Rays ◽  
X Ray ◽  
Mass Ratios ◽  
X Ray Binaries ◽  
Eddington Limit

Context. The origin and number of the Galactic supergiant X-ray binaries is currently not well understood. They consist of an evolved massive star and a neutron star or black-hole companion. X-rays are thought to be generated from the accretion of wind material donated by the supergiant, while mass transfer due to Roche-lobe overflow is mostly disregarded because the high mass ratios of these systems are thought to render this process unstable. Aims. We investigate how the proximity of supergiant donor stars to the Eddington limit, and their advanced evolutionary stage, may influence the evolution of massive and ultra-luminous X-ray binaries with supergiant donor stars (SGXBs and ULXs). Methods. We constructed models of massive stars with different internal hydrogen and helium gradients (H/He gradients) and different hydrogen-rich envelope masses, and exposed them to slow mass-loss to probe the response of the stellar radius. In addition, we computed the corresponding Roche-lobe overflow mass-transfer evolution with our detailed binary stellar evolution code, approximating the compact objects as point masses. Results. We find that a H/He gradient in the layers beneath the surface, as it is likely present in the well-studied donor stars of observed SGBXs, can enable mass transfer in SGXBs on a nuclear timescale with a black-hole or a neutron star accretor, even for mass ratios in excess of 20. In our binary evolution models, the donor stars rapidly decrease their thermal equilibrium radius and can therefore cope with the inevitably strong orbital contraction imposed by the high mass ratio. We find that the orbital period derivatives of our models agree well with empirical values. We argue that the SGXB phase may be preceded by a common-envelope evolution. The envelope inflation near the Eddington limit means that this mechanism more likely occurs at high metallicity. Conclusion. Our results open a new perspective for understanding that SGBXs are numerous in our Galaxy and are almost completely absent in the Small Magellanic Cloud. Our results may also offer a way to find more ULX systems, to detect mass transfer on nuclear timescales in ULX systems even with neutron star accretors, and shed new light on the origin of the strong B-field in these neutron stars.

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 Torque Reversals in Disk Accreting Pulsars

1998 ◽  
Vol 15 (2) ◽  
pp. 250-253
Author(s):  
Jianke Li ◽  
Dayal T. Wickramasinghe
Keyword(s):  
Neutron Star ◽  
Binary System ◽  
Recent Work ◽  
Time Scale ◽  
Accretion Rate ◽  
Future Studies ◽  
X Ray ◽  
The Past ◽  
X Ray Binaries ◽  
Coherent Picture

AbstractX-ray binaries in which the accreting component is a neutron star commonly exhibit significant changes in their spin. In the system Cen X-3, a disk accreting binary system, the pulsar was observed to spin up at a rate ḟ = 8 × 10−13 Hz s−1 when averaged over the past twenty years, but significant fluctuations were observed above this mean. Recent BASTE observations have disclosed that these fluctuations are much larger than previously noted, and appeared to be a system characteristic. The change in the spin state from spin-up to spin-down or vice-versa occurs on a time scale that is much shorter than the instrument can resolve (≤1 d), but appears always to be a similar amplitude, and to occur stochastically. These observations have posed a problem for the conventional torque–mass accretion relation for accreting pulsars, because in this model the spin rate is closely related to the accretion rate, and the latter needs to be finely tuned and to change abruptly to explain the observations. Here we review recent work in this direction and present a coherent picture that explains these observations. We also draw attention to some outstanding problems for future studies.

scholarly journals Early neutron star evolution in high-mass X-ray binaries

2020 ◽  
Vol 494 (1) ◽  
pp. 44-49 ◽  
Author(s):  
Wynn C G Ho ◽  
M J P Wijngaarden ◽  
Nils Andersson ◽  
Thomas M Tauris ◽  
F Haberl
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Thermal Emission ◽  
Equilibrium Phase ◽  
High Mass ◽  
X Ray ◽  
Spin Period ◽  
Long Duration ◽  
X Ray Binaries ◽  
The Magnetic Field

ABSTRACT The application of standard accretion theory to observations of X-ray binaries provides valuable insights into neutron star (NS) properties, such as their spin period and magnetic field. However, most studies concentrate on relatively old systems, where the NS is in its late propeller, accretor, or nearly spin equilibrium phase. Here, we use an analytic model from standard accretion theory to illustrate the evolution of high-mass X-ray binaries (HMXBs) early in their life. We show that a young NS is unlikely to be an accretor because of the long duration of ejector and propeller phases. We apply the model to the recently discovered ∼4000 yr old HMXB XMMU J051342.6−672412 and find that the system’s NS, with a tentative spin period of 4.4 s, cannot be in the accretor phase and has a magnetic field B > a few × 1013 G, which is comparable to the magnetic field of many older HMXBs and is much higher than the spin equilibrium inferred value of a few × 1011 G. The observed X-ray luminosity could be the result of thermal emission from a young cooling magnetic NS or a small amount of accretion that can occur in the propeller phase.

scholarly journals On the origin of Supergiant Fast X-ray Transients

2018 ◽  
Vol 14 (S346) ◽  
pp. 193-196
Author(s):  
Swetlana Hubrig ◽  
Lara Sidoli ◽  
Konstantin A. Postnov ◽  
Markus Schöller ◽  
Alexander F. Kholtygin ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Stellar Wind ◽  
Longitudinal Magnetic Field ◽  
High Mass ◽  
Large Telescope ◽  
X Ray ◽  
Very Large Telescope ◽  
Low X ◽  
X Ray Binaries

Abstract. A fraction of high-mass X-ray binaries are supergiant fast X-ray transients. These systems have on average low X-ray luminosities, but display short flares during which their X-ray luminosity rises by a few orders of magnitude. The leading model for the physics governing this X-ray behaviour suggests that the winds of the donor OB supergiants are magnetized. In agreement with this model, the first spectropolarimetric observations of the SFXT IGR J11215-5952 using the FORS 2 instrument at the Very Large Telescope indicate the presence of a kG longitudinal magnetic field. Based on these results, it seems possible that the key difference between supergiant fast X-ray transients and other high-mass X-ray binaries are the properties of the supergiant’s stellar wind and the physics of the wind’s interaction with the neutron star magnetosphere.

scholarly journals Probing the stellar wind geometry in Vela X-1 with infrared interferometry

2012 ◽  
Vol 8 (S290) ◽  
pp. 197-198
Author(s):  
Élodie Choquet ◽  
Pierre Kervella ◽  
Jean-Baptiste Le Bouquin ◽  
Antoine Mérand ◽  
Xavier Haubois ◽  
...  
Keyword(s):  
Neutron Star ◽  
High Mass ◽  
Resolution Limit ◽  
X Ray ◽  
Upper Limit ◽  
Accretion Process ◽  
Massive Neutron Star ◽  
Infrared Interferometry ◽  
X Ray Binaries ◽  
K Band

AbstractHigh-mass X-ray Binaries (HMXBs) are keys to study stellar remnants that are otherwise extremely faint and difficult to observe when isolated. Vela X-1 is a well-known eclipsing HMXB composed of a very massive neutron star orbiting a B0.5I supergiant with a period of 9 days. The supergiant wind is the main feeding material for the accreting neutron star, and its properties are of prime interest to understand the physics at stakes in the accretion process.In order to characterize the geometry and physical properties of the dense wind at a scale of a few stellar radii, we obtained infrared interferometric observations of Vela X-1 in 2010 using the VLTI/AMBER instrument in the K band (2.2 μm), and in 2012 using the VLTI/PIONIER instrument in the H band (1.6 μm).Although the apparent disk of the supergiant and the orbital separation of the two objects are beyond the present resolution limit of the VLTI, the K-band observations partially resolve the wind envelope on the two longest baselines. We were able to measure the radius of 265±82 R⊙ for the circumstellar wind at a temperature of 1300 K, assuming a distance of 1.9 kpc. The H-band observations do not resolve the system, and we were able to set an upper limit of 112 R⊙ for the envelope radius at a temperature of 1800 K.

scholarly journals Evidence from high-mass X-ray binaries that Galactic WR components of WR+O binaries end their life with a supernova explosion

2020 ◽  
Vol 636 ◽  
pp. A99 ◽  
Author(s):  
D. Vanbeveren ◽  
N. Mennekens ◽  
E. P. J. van den Heuvel ◽  
J. Van Bever
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Supernova Explosion ◽  
Solar Neighborhood ◽  
High Mass ◽  
Population Number ◽  
X Ray ◽  
Theoretical Population ◽  
X Ray Binaries

Context. Theoretical population number studies of binaries with at least one black hole (BH) component obviously depend on whether or not BHs receive a (natal) kick during their formation. Aims. Several observational facts seem to indicate that BHs do indeed receive a kick during their formation. In the present paper, we discuss additional evidence of this. Methods. The progenitors of wind-fed high-mass X-ray binaries (HMXB) with a BH component (BH HMXB) are WR+OB binaries where the Wolf–Rayet (WR) star will finally collapse and form the BH. Starting from the observed population of WR+OB binaries in the solar neighborhood, we predict the population of wind-fed BH HMXBs as a function of the BH-natal kick. Results. The simulations reveal that when WR stars collapse into a BH with a zero or low kick, we should expect 100 or more wind-fed BH HMXBs in the solar neighborhood, whereas only one is observed (Cyg X-1). We consider this as evidence that either WR components in binaries end their life as a neutron star or that they collapse into BHs, both accompanied by a supernova explosion imparting significant (natal) kicks.

scholarly journals Clumpy wind accretion in supergiant neutron star high mass X-ray binaries

2016 ◽  
Vol 589 ◽  
pp. A102 ◽  
Author(s):  
E. Bozzo ◽  
L. Oskinova ◽  
A. Feldmeier ◽  
M. Falanga
Keyword(s):  
Neutron Star ◽  
High Mass ◽  
X Ray ◽  
X Ray Binaries

scholarly journals Probing the X-ray Variability of X-ray Binaries

2003 ◽  
Vol 214 ◽  
pp. 236-239
Author(s):  
Wenfei Yu
Keyword(s):  
Neutron Star ◽  
Light Curve ◽  
Time Scale ◽  
Accretion Rate ◽  
Power Spectra ◽  
The Other ◽  
Periodic Oscillations ◽  
X Ray ◽  
Orbital Frequency ◽  
X Ray Binaries

Kilohertz quasi-periodic oscillations (kHz QPOs) has been regarded as representing the Keplerian frequency at the inner disk edge in the neutron star X-ray binaries. The so-called “parallel tracks” on the plot of the kHz QPO frequency vs. X-ray flux in neutron star X-ray binaries, on the other hand, show the correlation between the kHz QPO frequency and the X-ray flux on time scales from hours to days. This is suspected as caused by the variations of the mass accretion rate through the accretion disk surrounding the neutron star. We show here that by comparing the correlation between the kHz QPO frequency and the X-ray count rate on a certain QPO time scale observed approximately simultaneous in the Fourier power spectra of the X-ray light curve, we have found evidences that the X-ray flux of millihertz QPOs in neutron star X-ray binaries is generated inside the inner disk edge if adopting that the kilohertz QPO frequency is an orbital frequency at the inner disk edge.

scholarly journals Orbital and superorbital periods in ULX pulsars, disc-fed HMXBs, Be/X-ray binaries, and double-periodic variables

2020 ◽  
Vol 495 (1) ◽  
pp. L139-L143
Author(s):  
L J Townsend ◽  
P A Charles
Keyword(s):  
Neutron Star ◽  
Orbital Period ◽  
Binary Systems ◽  
High Mass ◽  
Early Type ◽  
Present Evidence ◽  
X Ray ◽  
Spin Period ◽  
Simple Linear Relationship ◽  
X Ray Binaries

ABSTRACT We present evidence for a simple linear relationship between the orbital period and superorbital period in ultra-luminous X-ray (ULX) pulsars, akin to what is seen in the population of disc-fed neutron star supergiant X-ray binary and Be/X-ray binary systems. We argue that the most likely cause of this relationship is the modulation of precessing hotspots or density waves in an accretion or circumstellar disc by the binary motion of the system, implying a physical link between ULX pulsars and high-mass X-ray binary (HMXB) pulsars. This hypothesis is supported by recent studies of Galactic and Magellanic Cloud HMXBs accreting at super-Eddington rates, and the position of ULX pulsars on the spin period–orbital period diagram of HMXBs. An interesting secondary relationship discovered in this work is the apparent connection between disc-fed HMXBs, ULXs, and a seemingly unrelated group of early-type binaries showing so-called double-periodic variability. We suggest that these systems are good candidates to be the direct progenitors of Be/X-ray binaries.

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