TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3824
SUBJECT: Swift Trigger 150823 is HETE J1900.1-2455
DATE:    05/08/17 21:32:01 GMT
FROM:    Hans Krimm at NASA-GSFC  <krimm@milkyway.gsfc.nasa.gov>

L. Barbier (GSFC), S. Barthelmy (GSFC), J. Cummings (GSFC/NRC),
E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (GSFC/UMD),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), J. Nousek (PSU),
D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC),
G. Sato (ISAS), M. Tripicco (GSFC/SSAI), J. Tueller (GSFC)
on behalf of the Swift-BAT team:

Swift Trigger 150823 (previously designated GRB 050817) (GCN 3819,
Fox et al.) is very likely to be a thermonuclear X-ray burst from the
millisecond pulsar HETE J1900.1-2455 (ATEL #516, Vanderspek et al.).

This conclusion is based on the following facts derived from analysis
of the full BAT data set.  The ground-refined position of the source
(R.A.,Dec.) = (285.021, -24.907) is within  1.1 arcmin of
HETE J1900.1-2455  (position from ATEL #526, Fox et al.),
a known burster (ATEL #534, Kawai et al).  The spectrum is very soft,
with a blackbody temperature of kT ~3 keV and no significant emission
above 25 keV.  The temporal profile shows two peaks, of ~4  and
~6 second duration, respectively, separated by ~10 seconds.
The centers of the peaks were at T-10 seconds and T+0 seconds,
respectively, compared to the BAT trigger time of 12:19:58 UT.
This structure is similar to a double-peaked radius-expansion X-ray burst
expected from a neutron star (note that Kawai et al., ATEL #534, have
already detected a radius-expansion burst from this source).

Based on these facts, we retract the GRB designation for
Swift Trigger 150823.