The average broad band 5-500 keV JEM-X (61.6 ks) plus IBIS/ISGRI (63.9 ks) spectrum can be well fit by a power-law with exponential cut-off at high energy: Γ=1.29±0.04, Ecut=(122±10) keV (χ2=0.9 for 19 d.o.f., 1% systematic uncertainty). The 5-100 keV flux is (8.3±0.3)×10-9 erg/s/cm2. No significant features appear in the 3-35 keV JEM-X light curve (time bins 2 s-10 min).
The source presents a monotonically increasing flux in all bands: the continuous coverage by IBIS/ISGRI shows that the 20-40 keV flux at the beginning of the observation was 63±4 mCrab and reached 617±26 mCrab at its end. By comparing the corresponding rise in the harder 40-80 keV band from 78±5 to 805±40 mCrab and performing a linear fit to the hardness ratio, we found significant evidence (~8σ c.l.) of a spectral softening with time.
On the base of the rapid flux increase, the high value of the energy cut-off and the absence of thermonuclear bursts, we argue that Swift J174510.8-262411 might be a new black-hole transient.
Further observations at all wavelengths are encouraged to unveil the nature of this source.
We thank the INTEGRAL Galactic bulge monitoring group for their collaboration.
|Publication date||17 Sep 2012|
|Publication status||Published - 17 Sep 2012|
|Series||The Astronomer's telegram|
- Gamma ray