Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userObservations of The High Mass X-ray Binary A0535+26 in Quiescence
134
0
0.0
(
0
)
Added by
Richard E. Rothschild
Publication date
2013
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
We have analyzed 3 observations of the High Mass X-ray Binary A0535+26 performed by the Rossi X-ray Timing Explorer (RXTE) 3, 5, and 6 months after the last outburst in 2011 February. We detect pulsations only in the second observation. The 3-20 keV spectra can be fit equally well with either an absorbed power law or absorbed thermal bremsstrahlung model. Re-analysis of 2 earlier RXTE observations made 4 years after the 1994 outburst, original BeppoSAX observations 2 years later, re-analysis of 4 EXOSAT observations made 2 years after the last 1984 outburst, and a recent XMM-Newton observation in 2012 reveal a stacked, quiescent flux level decreasing from ~2 to <1 x 10^{-11} ergs/cm2/s over 6.5 years after outburst. Detection of pulsations during half of the quiescent observations would imply that accretion onto the magnetic poles of the neutron star continues despite the fact that the circumstellar disk may no longer be present. The accretion could come from material built-up at the corotation radius or from an isotropic stellar wind.
rate research
Read More
We present the long-term optical spectroscopic observations on the Be/X-ray binary A0535+26 from 1992 to 2010. Combining with the public V-band photometric data, we find that each giant X-ray outburst occurred in a fading phase of the optical brightness. The anti-correlation between the optical brightness and the H$alpha$ intensity during our 2009 observations indicates a mass ejection event had taken place before the 2009 giant X-ray outburst, which might cause the formation of a low-density region in the inner part of the disk. The similar anti-correlation observed around 1996 September indicates the occurrence of the mass ejection, which might trigger the subsequent disk loss event in A0535+26.
The optical behaviour of the Be star in the high-mass X-ray transient A0535+26/HDE245770 shows that at periastron the luminosity is typically enhanced by 0.02 to a few tenths magnitude, and the X-ray outburst occurs eight days after the periastron. Indeed, at the periastron an increase of the mass flux occurs. This sort of flush reaches the external part of the temporary accretion disk around the neutron star and moves to the hot central parts of the accretion disk and the neutron star surface. The time necessary for this way is dependent on the turbulent viscosity in the accretion disk, as discussed by Giovannelli, Bisnovatyi-Kogan, and Klepnev (2013) (GBK13). In this paper we will show the behaviour of this system in optical band around the predicted periastron passage on 21st February 2014, by using the GBK13 ephemeris that we used to schedule our spectroscopic and photometric optical observations. Spectroscopic unusual activity detected in the Balmer lines and the enhancement in the emission in B, V, and R bands around the periastron passage, and the subsequent X-ray event definitively demonstrate the existence of about 8 day delay between optical and X-ray flares.
We present the results of the observations of the giant bursts from the X-ray pu lsar A0535+26 made by HEXE onboard Mir-Kvant in April 1989, November 1993 and February 1994. The pulse periods were measured, pulse profiles in different energy bands were produced, and their variability was investigated. The power density spectra (PDS) in 2x10^(-3)-1 Hz range is presented, which shape is typical for flicker-noise processes, usually observed in black hole candidates. The noise rms grows with energy from ~20% at 20 keV to ~30% at 80 keV. The source photon spectrum in the 15-200 keV energy range and its variability over the pulse phase are reported. Approximately the shape of the spectrum can be described by the canonical model for X-ray pulsars with power-law index g~1.1, cut-off energy E_c~23 keV and folding energy E_f~19 keV. All these parameters are weakly dependent on the luminosity. The most significant deviation from this continuum is observed at ~100 keV in the spectrum of the main pulse maximum. This feature is interpreted as a cyclotron line. Comparison of the HEXE data with the data from BATSE/CGRO (Bildsten et al., 1997) shows that in the high luminosity state (L~10^38 erg/s) the pulsars pulse profile differs substantially from the pulse profile in the low-luminosity (L~5x10^36 erg/s) state. This difference is explained by the qualitative change of the polar cap structure with formation of the accretion columns.
The propeller effect should cut off accretion in fast-spinning neutron star high mass X-ray binaries (HMXBs) at low mass transfer rates. However, accretion continues in some HMXBs at $L_{x} < 10^{34}$ erg s$^{-1}$, as evidenced by continuing pulsations. Indications of spectral softening in systems in the propeller regime suggest that some HMXBs are undergoing fundamental changes in their accretion regime. A 39 ks textit{XMM-Newton} observation of the transient HMXB V0332+53 found it at a very low X-ray luminosity ($L_{x} sim 4times 10^{32}$ erg s${^{-1}}$). A power-law spectral fit requires an unusually soft spectral index ($4.4^{+0.9}_{-0.6}$), while a magnetized neutron star atmosphere model, with temperature lt 6.7$pm 0.2$ K and inferred emitting radius of $sim0.2-0.3$ km, gives a good fit. We suggest that the quiescent X-ray emission from V0332+53 is mainly from a hot spot on the surface of the neutron star. We could not detect pulsations from V0332+53, due to the low count rate. Due to the high $N_H$, thermal emission from the rest of the neutron star could be only weakly constrained, to lt $<$6.14$^{+0.05}_{-6.14}$ K, or $<3times10^{33}$ erg s${^{-1}}$.
We present the results obtained from analysis of two AstroSat observations of the high mass X-ray binary pulsar OAO 1657-415. The observations covered 0.681-0.818 and 0.808-0.968 phases of the $sim$10.4 day orbital period of the system, in March and July 2019, respectively. Despite being outside the eclipsing regime, the power density spectrum from the first observation lacks any signature of pulsation or quasi-periodic oscillations. However, during July observation, X-ray pulsations at a period of 37.0375 s were clearly detected in the light curves. The pulse profiles from the second observation consist of a broad single peak with a dip-like structure in the middle across the observed energy range. We explored evolution of the pulse profile in narrow time and energy segments. We detected pulsations in the light curves obtained from 0.808--0.92 orbital phase range, which is absent in the remaining part of the observation. The spectrum of OAO 1657-415 can be described by an absorbed power-law model along with an iron fluorescent emission line and a blackbody component for out-of-eclipse phase of the observation. Our findings are discussed in the frame of stellar wind accretion and accretion wake at late orbital phases of the binary.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
