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TOPIC: A0535+26

Blobrana

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Posts: 131433

Date: Feb 2 11:45 2015

RE: A0535+26	Permalink

ATel 7015: MAXI/GSC detection of the onset of the outburst from Be/X-ray binary pulsar A0535+26 __________________

Blobrana

L

Posts: 131433

Date: May 3 03:59 2013

High Mass X-ray Binary A0535+26	Permalink

Title: Observations of The High Mass X-ray Binary A0535+26 in Quiescence Authors: Richard Rothschild, Alex Markowitz, Paul Hemphill, Isabel Caballero, Katja Pottschmidt, Matthias Kuehnel, Joern Wilms, Felix Fuerst, Victor Doroshenko, Ascension Camero-Arranz We have analysed 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. Read more (135kb, PDF) __________________

Blobrana

L

Posts: 131433

Date: Mar 26 18:48 2013

A 0535+26	Permalink

Title: A0535+26 in the April 2010 outburst: probing the accretion regime at work Authors: Daniela Müller, Dmitry Klochkov, Isabel Caballero, Andrea Santangelo A number of accreting X-ray pulsars experience spectral changes, both on the long time scales and on the time scales of the neutron star spin period. The sources seem to form two distinct groups which differ by the type of the spectral variations with flux. Such a bimodality probably reflects two different regimes of accretion that may result in a particular pulsar depending on its luminosity - so-called sub- and super-critical regimes. We investigated the behaviour of the spectral parameters of the Be/X-ray binary system A 0535+26, as a function of flux and pulse phase. We used the data collected with INTEGRAL and RXTE during the April 2010 outburst of the source. We analysed the phase-averaged and phase-resolved spectra and performed pulse-to-pulse spectral analysis of the pulsar. Our analysis reveals variability in the continuum parameters of the pulse-averaged spectrum of the source with flux. The pulse-averaged cyclotron line energy does not change with the source luminosity during the outburst, which is consistent with previous studies. Our pulse-phase resolved and pulse-to-pulse analyses reveal, however, indications for a positive correlation of the cyclotron line energy with flux, as well as a flux-dependence of the continuum parameters. Based on the observed behaviour, we argue that A 0535+26 operates at the sub-critical accretion regime. Read more (355kb, PDF) __________________

Blobrana

L

Posts: 131433

Date: Jul 19 01:44 2011

A0535+26	Permalink

Title: The Be/X-ray binary A0535+26 during its recent 2009/2010 outbursts Authors: I. Caballero, K.Pottschmidt, A.Santangelo, L. Barragan, D. Klochkov, C. Ferrigno, J. Rodriguez, P. Kretschmar, S. Suchy, D. M. Marcu, D. Mueller, J. Wilms, I. Kreykenbohm, R. E. Rothschild, R. Staubert, M. H. Finger, A. Camero-Arranz, K. Makishima, T. Mihara, M. Nakajima, T. Enoto, W. Iwakiri, Y. Terada The Be/X-ray binary A0535+26 showed a giant outburst in December 2009 that reached ~5.14 Crab in the 15-50 keV range. Unfortunately, due to Sun constraints it could not be observed by most X-ray satellites. The outburst was preceded by four weaker outbursts associated with the periastron passage of the neutron star. The fourth of them, in August 2009, presented a peculiar double-peaked light curve, with a first peak lasting about 9 days that reached a (15-50 keV) flux of 440 mCrab. The flux then decreased to less than 220 mCrab, and increased again reaching 440 Crab around the periastron. The outburst was monitored with INTEGRAL, RXTE, and Suzaku TOO observations. One orbital period (~111 days) after the 2009 giant outburst, a new and unexpectedly bright outburst took place (~1.4Crab in the 15-50 keV range). It was monitored with TOO observations with INTEGRAL, RXTE, Suzaku, and Swift. First results of the spectral and timing analysis of these observations are presented, with a specific focus on the cyclotron lines present in the system and its variation with the mass accretion rate. Read more (230kb, PDF) __________________

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