GCN Circular 23882
J. A. Kennea (PSU), H. A. Krimm (NSF/USRA), K. L. Page (U Leicester) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 14:28:41 UT, the Swift Burst Alert Telescope (BAT) triggered and located 4U 1901+03 (trigger=888312). The BAT on-board calculated location is RA, Dec 285.972, +3.242 which is RA(J2000) = 19h 03m 53s Dec(J2000) = +03d 14' 30" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). This source, 4U 1901+03 is a HMXB X-ray pulsar, which appears to be going into another outburst. The rate has been rising in the Swift/BAT transient monitor since 6 February 2019 (MJD 58520) - see https://swift.gsfc.nasa.gov/results/transients/weak/4U1901p03/ - and is currently at 0.016 +/- 0.005 ct s^-1 cm^-2 (15-50 keV; 70 mCrab). The rise is also seen in MAXI. The last reported outburst of this source was in December 2011 (Sootome et al., ATel 3829). Due to a Sun observing constraint, Swift cannot slew to the BAT position until 13:00 UT on 2019 February 17. There will thus be no XRT or UVOT data for this trigger before this time.