INTEGRAL detects renewed activity from the microquasar XTE J1908+094
ATel #12628; J. Rodriguez (CEA Saclay/lab AIM, Fr), I. Mereminskiy (IKI RAS, Ru), S. A. Grebenev (IKI RAS, Ru), F. Cangemi (CEA, Fr), M. Clavel (IPAG, Fr), A. Coleiro (APC, Fr), E. Egron (INAF, It), Victoria Grinberg (IAAT, Ge), K. Pottschmidt (CRESST/UMBC/NASA-GSFC, USA), R. Remillard (MIT, USA), J. Steiner (CfA, USA), J. Tomsick (UCB/SSL, USA), J. Wilms (ECAP, Ge)
on 3 Apr 2019; 19:53 UT
Credential Certification: Jerome Rodriguez (jrodriguez@cea.fr)
Subjects: X-ray, Gamma Ray, Request for Observations, Black Hole, Transient
During the first observation of the AO 16 monitoring campaign on GRS 1915+105, performed on 2019 Apr. 1st from 6h24 to 20h45 UTC, INTEGRAL/IBIS detected significant emission from a source positionally coincident with XTE J1908+094.
XTE J1908+094 is an X-ray binary discovered during an outburst in 2002, reaching 90 mCrab at 2-10 keV, and was soon identified as source containing a black hole candidate as primary (Gogus et al. 2004, ApJ, 609, 977). The source underwent another outburst in 2013 (ATel #5523) during which a roughly flat radio spectrum and later optically thin synchrotron emission were detected in
radio (ATel #5530; ATel #5575) confirming the source as a microquasar (see e.g. Rushton et al. 2017 MNRAS, 468, 2788).
The source is detected with IBIS in both the 30-50 keV and 50-100 keV energy ranges at 15.5 and 7.2 σ respectively.
The 20-50 keV source fitted position is RA=19h 08m 53s DEC=+09deg 23.4min with a 90% uncertainty of about 2 arcmin. The catalogued position of XTE J1908+094 is ~0.3 arcmin away from the INTEGRAL fitted position, well within the 90% error box.
The 30-50 and 50-100 keV fluxes are 2.4 cts/s (~9 mCrab) and 1.3 cts/s (~14 mCrab) respectively, indicative of a hard spectrum.
A very preliminary spectral analysis indicates that the source spectrum is compatible with a power law model. The photon index is rather soft (2.3 +/- 0.5) even if it is still compatible with a hard state within the errors. However, we note that contamination of
some of the spectral bins by nearby sources including GRS 1915+105 could lead to an artificial softening of the spectrum. The 30-100 keV flux obtained from this model is 2e-10 erg/cm2/s (or about 10 mCrab).
We conclude that we detected probable renewed activity from the microquasar XTE J1908+094. The source may currently be in the early hard state of an ongoing outburst.
Multiwavelength observations, especially in radio, are strongly encouraged.