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Swift confirm renewed activity of the transient neutron star X-ray binary Aql X-1

ATel #6286; A. Meshcheryakov (IKI; Moscow, Russia), S. Tsygankov (FINCA; Tuorla Observatory, Finland)
on 1 Jul 2014; 18:56 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Alexander Meshcheryakov (mesch@iki.rssi.ru)

Subjects: X-ray, Neutron Star, Transient

Referred to by ATel #: 6447, 7088, 7095, 9287

Following the recent report of the brightening of the optical counterpart of the transient neutron star X-ray binary Aql X-1 between June 28 and 29 (ATel #6280), we observed the source with Swift on June 30 and July 01. XRT instrument was operated mainly in the photon counting mode with total exposure time 3.9 ks. The source is clearly seen in our observation. The X-ray spectrum of the source can be described by an absorbed power-law model with a hydrogen column density of N_H = (1.0 +/- 0.16)E22 cm-2 and a photon index of 2.34 +/-0.18. The inferred 0.3-10 keV unabsorbed flux is Fx=(1.23+/-0.32)E-10 erg/cm2/s, which translates into an isotropic luminosity of Lx ~ 3.7E35 erg/s for a distance of 5 kpc. This is about two orders of magnitude above the quiescent level of the source (~4e33erg/s). The Swift observations confirm a renewed accretion activity in Aql X-1. We thank Neil Gehrels and the Swift science team for making these observations possible. Analysis of the XRT data was performed utilizing the methods described by Evans et al. (2009, MNRAS, 397, 1177) and Evans et al. (2007, A&A, 469, 379). Further observations of Aql X-1 during accretion outburst in X-ray,UV,Optical,IR and Radio bands are highly encouraged.