A. P. Beardmore (U Leicester), J.D. Gropp (PSU),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),
M. H. Siegel (PSU) and A. Tohuvavohu (U Toronto) report on behalf of
the Neil Gehrels Swift Observatory Team:
At 16:17:00 UT, the Swift Burst Alert Telescope (BAT) triggered and
located Cyg X-1 (trigger=1069242). Swift slewed immediately to the source.
The BAT on-board calculated location is
RA, Dec 299.819, +35.277 which is
RA(J2000) = 19h 59m 16s
Dec(J2000) = +35d 16' 37"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). This onboard position is 12 arcminutes from the
known position of Cyg X-1, likely due to higher than typical attitude
uncertainty from the star trackers.
As is typical for an image trigger the prompt BAT lightcurve shows no
evidence of structure, and the significance of the source in the BAT image
is consistent with the typical brightness of Cyg X-1.
The XRT began observing the field at 16:19:20.2 UT, 139.8 seconds after
the BAT trigger. XRT found a bright X-ray source in the field-of-view 26
arcseconds from the position of Cyg X-1, but given the star trackers
had lost lock is likely consistent with this source.
There are no UVOT data available at this time.