TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  3997
SUBJECT: Swift-BAT trigger 155535 is definitely not a GRB
DATE:    05/09/17 15:46:06 GMT
FROM:    Hans Krimm at NASA-GSFC  <krimm@milkyway.gsfc.nasa.gov>

D. Grupe (PSU), H. Krimm (GSFC/USRA), P. Roming (PSU), P. Brown (PSU),
D. Burrows (PSU), J. Kennea (PSU), D. Palmer (LANL), A. Parsons (GSFC)
on behalf of the Swift team:

Using the full BAT data from the recent telemetry downlink, the Swift-BAT
trigger 155535 (at 13:19:00 UT on 17 September 2005) is not due to a GRB.
This was a cascade shower event from a high energy cosmic ray in the 
spacecraft.

The XRT started to observe the field of trigger #155535 175 s after 
the trigger.
The field was observed for 618 s in PC mode, but XRT did not detect any source.

The UVOT began observing the position of trigger #155535 at 13:20:19.2 UT, 80 s
after the BAT trigger. In the 100 s V-band image, no new source is detected
with respect to the DSS. The estimated extinction in this direction is
A_V ~0.5 magnitudes. The UVOT image gives 100% coverage of the BAT 
error circle.
The BAT source is located in a crowded star field.