* Astronomy

Title: The outburst of the X-ray nova GRS 1739-278 in September, 2016
Author: I.A. Mereminskiy (1), E.V. Filippova (1), R.A. Krivonos (1), S.A. Grebenev (1), R.A. Burenin (1), R.A. Sunyaev (1 and 2) ((1) Space Research Institute RAS, (2) Max Planck Institute for Astrophysics)

During the scanning observations of the Galactic Center region in August - September 2016 we detected the new outburst of the historical X-ray nova GRS 1739-278, the black hole candidate LMXB system. In this letter we present results of INTEGRAL and Swift-XRT observations taken during the outburst. In hard X-ray band (20-60 keV) the flux from the source raised from ~11 to ~30 mCrab between 3 and 14 of September. For nearly 8 days the source has been observed at this flux level and then faded to ~15 mCrab. The broadband quasi-simultaneous spectrum obtained during the outburst is well described by the absorbed powerlaw with the photon index Gamma=1.86±0.07 in broad energy range 0.5-150 keV, with absorption corresponding to N_H=2.3 x 10^22 cm^-2 assuming solar abundance. Based on this we can conclude that the source was in the low/hard state. From the lightcurve and spectra we propose that this outburst was 'failed', i.e. amount of accreted matter was not sufficient to achieve the high/soft spectral state with dominant soft blackbody component as seen in normal outbursts of black hole candidates.

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