HeI doubled emission lines from A0535+26 ≡ HDE 245770

Santangelo

et al. 2014

A&A

Accretion onto magnetized neutron stars is expected to be centrifugally inhibited at low accretion rates. Several sources, however, are known to pulsate in quiescence at luminosities below the theoretical limit predicted for the onset of the centrifugal barrier. The source 1A 0535+262 is one of them. Here we present the results of an analysis of a ∼50 ks long XMM-Newton observation of 1A 0535+262 in quiescence. At the time of the observation, the neutron star was close to apastron, and the source had remained quiet for two orbital cycles. In spite of this, we detected a pulsed X-ray flux of ∼3 × 10 −11 erg cm −2 s −1 . Several observed properties, including the power spectrum, remained similar to those observed in the outbursts. Particularly, we have found that the frequency of the break detected in the quiescent noise power spectrum follows the same correlation with flux observed when the source is in outburst. This correlation has been associated with the truncation of the accretion disk at the magnetosphere boundary. We argue that our result, along with other arguments previously reported in the literature, suggests that the accretion in quiescence also proceeds from an accretion disk around the neutron star. The proposed scenario consistently explains the energy of the cyclotron line observed in 1A 0535+262, and the timing properties of the source including the spin frequency evolution within and between the outbursts, and the frequency of the break in power spectrum.

Section: Discussionmentioning

confidence: 91%

XMM-Newtonobservations of 1A 0535+262 in quiescence

Santangelo

et al. 2014

A&A

“…Assuming that the rotation axis of the neutron star is perpendicular to the orbital plane, the inclination of the system is identical to the direction of observation i = Θ 0 . Giovannelli et al (2007) determined an inclination for the system of i = 37 ± 2 • . We can therefore obtain the location of the poles Θ 1 and Θ 2 .…”

Section: From Single-pole Pulse Profiles To Geometry and Beam Patternmentioning

confidence: 99%

Analyzing X-ray pulsar profiles: geometry and beam pattern of A 0535+26

Caballero

Kraus

Santangelo

et al. 2011

A&A

Aims. We applied a decomposition method to the energy dependent pulse profiles of the accreting binary pulsar A 0535+26, in order to identify the contribution of the two magnetic poles of the neutron star and to obtain constraints on the geometry of the system and on the beam pattern. Methods. We analyzed pulse profiles obtained from RXTE observations in the X-ray regime. Basic assumptions of the method are that the asymmetry observed in the pulse profiles is caused by non-antipodal magnetic poles and that the emission regions have axisymmetric beam patterns. Results. Constraints on the geometry of the pulsar and a possible solution of the beam pattern are given. We interpreted the reconstructed beam pattern in terms of a geometrical model of a hollow column plus a halo of scattered radiation on the neutron star surface, which includes relativistic light deflection.

Proceedings of the Extreme Sky: Sampling the Universe Above 10 keV — PoS(extremesky2009)

“…Peculiar outburst of A 0535+26 observed with INTEGRAL, RXTE and Suzaku I. Caballero discussed by [29]. We will also search for possible QPOs, as already observed in the source in 1994 [23].…”

Section: Pos(extremesky2009)063mentioning

confidence: 71%

New outburst of A0535+26 observed with INTEGRAL, RXTE and Suzaku

Caballero¹,

Pottschmidt²,

Barragán³

et al. 2010

A normal outburst of the Be/X-ray binary system A0535+26 has taken place in August 2009. It is the fourth in a series of normal outbursts that have occured around the periastron passage of the source, but is unusual by starting at an earlier orbital phase and by presenting a peculiar double-peaked light curve. A first "flare" (lasting about 9 days from MJD 55043 on) reached a flux of 440 mCrab. The flux then decreased to less than 220 mCrab, and increased again reaching 440 mCrab around the periastron at MJD 55057. Target of Opportunity observations have been performed with INTEGRAL, RXTE and Suzaku. First results of these observations are presented, with special emphasis on the cyclotron lines present in the X-ray spectrum of the source, as well as in the pulse period and energy dependent pulse profiles of the source.