scholarly journals Warped disks during type II outbursts in Be/X-ray binaries: evidence from optical polarimetry

2018 ◽  
Vol 619 ◽  
pp. A19 ◽  
Author(s):  
P. Reig ◽  
D. Blinov
Keyword(s):  
Neutron Star ◽  
Structural Changes ◽  
Degree Of Polarization ◽  
Polarization Degree ◽  
Polarization Angle ◽  
Similar Amount ◽  
Type Ii ◽  
Line Profiles ◽  
X Ray ◽  
X Ray Binaries

Context. Current models that explain giant (type II) X-ray outbursts in Be/X-ray binaries (BeXB), are based on the idea of highly distorted disks. They are believed to occur when a misaligned and warped disk becomes eccentric, allowing the neutron star to capture a large amount of material. The BeXB 4U 0115+63 underwent two major outbursts in 2015 and 2017. Aims. Our aim is to investigate whether the structural changes in the disk expected during type II outbursts can be detected through optical polarimetry. Methods. We present the first optical polarimetric observations and new optical spectra of the BeXB 4U 0115+63 covering the period 2013–2017. We study in detail the shape of the Hα line profile and the polarization parameters before, during, and after the occurrence of a type II X-ray outburst. Results. We find significant changes in polarization degree and polarization angle and highly distorted line profiles during the 2017 X-ray outburst. The degree of polarization decreased by ∼1%, while the polarization angle, which is supposed to be related with the disk orientation, first increased by ∼10° in about two months and then decreased by a similar amount and on a similar timescale once the X-ray activity ceased. Conclusions. We interpret the polarimetric and spectroscopic variability as evidence for the presence of a warped disk.

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 The X-ray Outbursts of Be/X-ray Transients

2000 ◽  
Vol 175 ◽  
pp. 713-718 ◽  
Author(s):  
Ignacio Negueruela ◽  
Atsuo T. Okazaki
Keyword(s):  
Neutron Star ◽  
Type I ◽  
Type Ii ◽  
X Ray ◽  
Disc Model ◽  
Resonant Effect ◽  
X Ray Binaries

AbstractWe present a new scenario for the behaviour of Be/X-ray binaries based on long-term multiwavelength monitoring and the decretion disc model. The circumstellar discs of the primaries are truncated because of the tidal and resonant effect of the neutron star. The geometry of the systems and the value of viscosity determine the presence or absence of Type I X-ray outbursts. The interaction of a strongly disturbed disc with the neutron star originates Type II X-ray and optical outbursts.

scholarly journals A minimal timescale for the continuum in 4U 1608-52 and Aql X-1

2021 ◽  
Vol 502 (1) ◽  
pp. L72-L78
Author(s):  
K Mohamed ◽  
E Sonbas ◽  
K S Dhuga ◽  
E Göğüş ◽  
A Tuncer ◽  
...  
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Power Spectra ◽  
Light Curves ◽  
State Transitions ◽  
Strong Positive Correlation ◽  
Present Evidence ◽  
X Ray ◽  
X Ray Binaries ◽  
The Continuum

ABSTRACT Similar to black hole X-ray binary transients, hysteresis-like state transitions are also seen in some neutron-star X-ray binaries. Using a method based on wavelets and light curves constructed from archival Rossi X-ray Timing Explorer observations, we extract a minimal timescale over the complete range of transitions for 4U 1608-52 during the 2002 and 2007 outbursts and the 1999 and 2000 outbursts for Aql X-1. We present evidence for a strong positive correlation between this minimal timescale and a similar timescale extracted from the corresponding power spectra of these sources.

scholarly journals A Machine Learning Approach For Classifying Low-mass X-ray Binaries Based On Their Compact Object Nature

2020 ◽  
Author(s):  
R Pattnaik ◽  
K Sharma ◽  
K Alabarta ◽  
D Altamirano ◽  
M Chakraborty ◽  
...  
Keyword(s):  
Machine Learning ◽  
Black Hole ◽  
Neutron Star ◽  
Binary Systems ◽  
Compact Object ◽  
X Ray ◽  
Average Accuracy ◽  
Machine Learning Approach ◽  
Low Mass ◽  
X Ray Binaries

Abstract Low Mass X-ray binaries (LMXBs) are binary systems where one of the components is either a black hole or a neutron star and the other is a less massive star. It is challenging to unambiguously determine whether a LMXB hosts a black hole or a neutron star. In the last few decades, multiple observational works have tried, with different levels of success, to address this problem. In this paper, we explore the use of machine learning to tackle this observational challenge. We train a random forest classifier to identify the type of compact object using the energy spectrum in the energy range 5-25 keV obtained from the Rossi X-ray Timing Explorer archive. We report an average accuracy of 87±13% in classifying the spectra of LMXB sources. We further use the trained model for predicting the classes for LMXB systems with unknown or ambiguous classification. With the ever-increasing volume of astronomical data in the X-ray domain from present and upcoming missions (e.g., SWIFT, XMM-Newton, XARM, ATHENA, NICER), such methods can be extremely useful for faster and robust classification of X-ray sources and can also be deployed as part of the data reduction pipeline.

DO YOUNG NEUTRON STARS WHICH SHOW THEMSELVES AS AXPs AND SGRs ACCRETE?

2003 ◽  
Vol 12 (05) ◽  
pp. 825-831 ◽  
Author(s):  
S. O. TAGIEVA ◽  
E. YAZGAN ◽  
A. ANKAY
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Supernova Explosion ◽  
X Ray ◽  
X Ray Binaries

We examined the fall-back disk models, and in general accretion, proposed to explain the properties of AXPs and SGRs. We checked the possibility of some gas remaining around the neutron star after a supernova explosion. We also compared AXPs and SGRs with the X-ray pulsars in X-ray binaries. We conclude that the existing models of accretion from a fall-back disk are insufficient to explain the nature of AXPs and SGRs.

scholarly journals Hardness Ratio in Evolving Low-Mass X-ray Binary Systems

1987 ◽  
Vol 125 ◽  
pp. 199-199
Author(s):  
J. Shaham ◽  
M. Tavani
Keyword(s):  
Neutron Star ◽  
Accretion Disk ◽  
Binary Systems ◽  
Spectral Component ◽  
Soft Component ◽  
Hard Component ◽  
X Ray ◽  
Low Mass ◽  
Additional Support ◽  
X Ray Binaries

Spectral observations of low-mass X-ray binaries (LMXBs) show that the soft component usually dominates over the hard one. These results provide additional support to an interpretation based on models of LMXBs in which the neutron star while, on the average, spinning up, is also experiencing a spinning down torque. Under these conditions, a fraction of the luminosity associated with the gravitational release of energy on the surface of the accreting neutron star may manifest itself as luminosity originating in the inner part of the accretion disk. It is probably possible to separate the two contributions; the stellar luminosity can be associated with the hard component of the spectrum and the disk luminosity, related to the exchange of energy due to the torque between the rapidly spinning neutron star and the accretion disk, can be associated with the soft spectral component.

scholarly journals GRO J1744-28 and the Rapid Burster; Bizarre Objects!

1998 ◽  
Vol 188 ◽  
pp. 111-111
Author(s):  
Walter H.G. Lewin
Keyword(s):  
Type Ii ◽  
Time Intervals ◽  
Periodic Oscillations ◽  
X Ray ◽  
Magnetic Dipole Field ◽  
Order Of Magnitude ◽  
Low Mass ◽  
Type Ii Bursts ◽  
The Difference ◽  
X Ray Binaries

The bursts from GRO J1744-28 are due to accretion instabilities as is the case for type II bursts in the Rapid Burster. Both sources are transient Low-Mass X-ray Binaries, and they both exhibit unusual quasi-periodic-oscillations in their persistent X-ray flux following several (not all) of the type II bursts. There are important differences too. GRO J1744-28 is an X-ray pulsar; the Rapid Burster is not. In addition, the pattern of bursts and the burst peak luminosities are very different for the two sources. Time intervals between the rapidly repetitive bursts in the Rapid Burster can be as short as 10 sec, in 1744-28 they are as short as 200 sec. The peak luminosities of the bursts from GRO J1744-28 can exceed the Eddington luminosity (for assumed isotropic emission) by one to two orders of magnitude. The QPO centroid frequencies (see above) differ by an order of magnitude (~0.04 Hz for the Rapid Burster, and 0.3 Hz for GRO J1744-28). The difference in behavior p obably lies in the difference in the magnetic dipole field strength of the accreting neutron stars (for GRO J1744-28 it is almost certainly much higher than for the Rapid Burster). It remains puzzling, why GRO J1744-28 and the Rapid Burster are the only known sources which exhibit rapidly repetitive type II bursts.

Sign in / Sign up

Export Citation Format

Share Document