Swift Spectroscopy of the Black Hole GS 1354-645 in Outburst
ATel #7614; J. M. Miller, M. T. Reynolds (University of Michigan), J. Kennea (Penn State)
on 10 Jun 2015; 16:21 UT
Credential Certification: Jon Miller (jonmm@umich.edu)
Subjects: X-ray, Black Hole
We report on a Swift/XRT observation of GS 1354-645 obtained in
windowed timing mode. The 0.45 ks observation started on 2015-06-10
at 09:55:15. The fast read-out of windowed timing mode prevents
photon pile-up and yields robust spectra and flux measurements for
bright sources.
After binning to require 10 counts per bin, an absorbed power-law is
found to provide an acceptable fit to the 1-10 keV spectrum. The
column density is measured to be N_H = 6.4 +/- 1.2 E+21 cm^-2, the
power-law index is found to be 1.5 +/- 0.1 (1 sigma errors). This
model implies an absorbed flux of 1.7 E-10 erg/s/cm^2 in the 0.5-10.0
keV band, or an unabsorbed flux of 2.25 E-10 erg/s/cm^2. The
luminosity of the source is then 1.7 E+37 (d/25 kpc)^2 erg/s (Casares
et al. 2009).
The windowed timing mode spectrum is softer, and the source is more
luminous than implied by the photon counting mode XRT observation, as
anticipated in ATEL #7612. The source is currently 1500 times
brighter than its quiescent level (Reynolds & Miller 2011).
Continued X-ray observations, and radio observations, are strongly
encouraged.
Casares, J., et al., 2009, ApJS, 181, 238
Reynolds, M. T., & Miller, J. M., 2011, ApJ, 734, L17