TITLE:   GCN CIRCULAR
NUMBER:  22966
SUBJECT: Swift detects a flare  from AX 1631.9-4752 
DATE:    18/07/19 14:39:53 GMT
FROM:    Boris Sbarufatti at PSU  <bxs60@psu.edu>

B. Sbarufatti (PSU), S. D. Barthelmy (GSFC), S. W. K Emery (UCL-MSSL), J.D. Gropp (PSU), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), M. J. Moss (George Washington University), D. M. Palmer (LANL), P. Romano (INAF-OAB), and A. Tohuvavohu (PSU) report on behalf of the
Neil Gehrels Swift Observatory Team:


The Swift Burst Alert Telescope (BAT) triggered on the high mass X-ray binary AX 1631.9-4752 on 2018 July 18 at 14:04:34 UT (image trigger 848584). Swift did not slew to the target, a ToO observation was performed to obtain NFI data. 

The XRT began observing the field about 12ks after the BAT trigger. The XRT light curve shows flaring with a count rate ranging between 0.3 and 0.7 cps, a factor of 2-4 higher than the average XRT cont rate for this source, but comparable with the last observation performed (on 2018 May 16). 

The mean XRT/PC spectrum (1ks exposure) can be fit by an absorbed power-law model with a photon index of 0.1 (+1.0, -0.9) and an absorbing column density of NH=(3.9+1.8-1.4)E23 cm^-2. The average 0.3-10 keV observed (unabsorbed) flux is 9.7E-11 (1.96E-10) erg cm^-2 s^-1.  


The historical light curve from the BAT hard X-ray transient monitor (Krimm et al, 2013, ApJS, 209, 14; 15-50 keV) can be found at https://swift.gsfc.nasa.gov/results/transients/AXJ1631.9-4752/ .

[GCN OPS NOTE(20jul18):  Per author's request, the source name in the first paragraph 
was changed from "IGR J16418-4532" to "AX 1631.9-4752".]