TITLE:   GCN CIRCULAR
NUMBER:  12329
SUBJECT: GRB 110905A: Potential BAT trigger on MAXI J1836-194
DATE:    11/09/05 08:04:30 GMT
FROM:    Derek Fox at PSU  <dfox@astro.psu.edu>

Derek B. Fox (Penn State) reports: 

"The new R~16 mag optical source identified by Li & Filippenko (GCN
12328) in their follow-on observations of the recent Swift BAT image
trigger 502415 / GRB 110905A (Pagani et al., GCN 12327), is almost
certainly the optical counterpart to the recently-discovered X-ray
transient MAXI J1836-194 (Negoro et al., ATel #3611).  This likely
black hole X-ray binary system has an associated optical (Kennea et
al., ATel #3613), NIR (Rau, Greiner & Sudilovsky, ATel #3619) and
radio (Miller-Jones et al., ATel #3628) counterpat with coordinate
position (most accurately known from EVLA observations) consistent to
<~1 arcsec with the optical source of Li & Fillippenko.

Given that BAT trigger #502415 is a BAT image trigger with
localization consistent with the position of the new transient, this
raises the question of whether BAT trigger #502415 was generated by
high-energy variability of MAXI J1836-194 itself rather than being due
to a bona fide gamma-ray burst.

If GRB 110905A is a genuine gamma-ray burst -- distinct from and
unrelated to MAXI J1836-194 -- the source reported by Li &
Fillippenko, being the optical counterpart of MAXI J1836-194, is
almost certainly not the burst's optical afterglow.

The author cites a private communication from J. Greiner as first to
point out this possible interpretation of events."