Swift observations confirm new outburst of MAXI J1957+032

ATel #8146; J. A. Kennea (PSU), P. A. Evans, A. P. Beardmore (U Leicester), H. A. Krimm (CRESST/GSFC/USRA), P. Romano (INAF-IASFPA), P. Curran (CEA-Saclay), K. Yamaoka (AGU), M. Serino (RIKEN) and H. Negoro (Nihon U.)
on 9 Oct 2015; 21:21 UT
Credential Certification: Jamie A. Kennea (kennea@astro.psu.edu)

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Starting 16:09UT on October 9th, 2015, Swift took a 1ks target-of-opportunity observation of MAXI J1956+032 (AKA IGR J19566+0326), which has been reported to be in a new outburst (Sugimoto et al., ATEL #8143). A source consistent with the previously reported Swift position of this X-ray transient (Cherepashchuk et al., ATEL #7506) was detected, with a UVOT enhanced position of: RA/Dec(J2000) = 299.16266, 3.44520, equivalent to:

RA(J2000) = 19h 56m 39.04s
Dec(J2000) = +03d 26m 42.7s

with an estimated uncertainty of 2.2 arc-seconds radius (90% confidence), at a count rate of 0.63 +/- 0.04 XRT count s^-1.

The XRT spectrum is well fit by an absorbed power-law model, with N_H = 4.4 +/- 1.1 x 10²¹ cm^-2 and photon index of 2.8 +/- 0.3. The 0.5-10 keV flux, uncorrected for absorption, is 1.7 +/- 0.2 x 10^-11 erg/s/cm², and approximately 5 x 10^-11 erg/s/cm² when corrected for absorption. Although this is not especially bright, it does confirm the re-brightening of this transient, and is slightly brighter than the peak brightness of this source seen in previous Swift observations, and a factor of ~70 brighter than seen in the last Swift observation of this transient on June 19th, 2015.

We have requested Swift monitoring of MAXI J1957+032 in order to track this outburst. Multi-wavelength observations are requested in order to determine the nature of this transient.