Sw J1745-26 still detected by Swift XRT in a lower, harder state.
ATel #4782; B. Sbarufatti (INAF-OAB/PSU), J. A. Kennea (PSU), M. C. Stroh (PSU), D. N. Burrows (PSU), P. A. Evans, A. P. Beardmore (U. Leicester), H. A. Krimm (CRESST/GFSC), N. Gehrels (GFSC)
on 3 Feb 2013; 16:17 UT
Credential Certification: Boris Sbarufatti (boris.sbarufatti@brera.inaf.it)
Subjects: X-ray, Transient
After Sw J1745-26 came out from the Sun constraint for the Swift narrow field instruments we resumed monitoring of this black-hole candidate. The first observation was performed on MJD 56325. Swift XRT still detects the source at a count rate of 10.4+/-0.2 counts/s, comparable with the emission level at discovery (ATel #4383), bus significantly lower than the value at peak, detected weeks before the source entered the observational constraint (ATel #4436).
The 0.5-10 keV spectrum can be fit by an absorbed powerlaw with Photon Index 1.4 +/-0.1 (compare with 2.28+/-0.2 on MJD 56197) and absorbing column of 1.0+/-0.1 cm^-2, in excess with respect to the Galactic value of 6.52E21 cm^-2 (Kalberla et al. 2005) . This shows that the source has considerably hardened since the last observation.
The absorption corrected flux in the 0.5-10 keV band decreased from 5.5E-8 erg cm^-2 s^-1 to 2.1E-9 erg cm^-2 s^-1.
The BAT lightcurve (http://heasarc.gsfc.nasa.gov/docs/swift/results/transients/weak/SwiftJ1745.1-2624/) also shows the source at a level comparable to the one detected at discovery, implying that the source went back to the Low Hard State (see ATel #4450)
All quoted errors are at 90% confidence level.
