GCN Circular 18571
H. A. Krimm (GSFC/USRA), S. D. Barthelmy (GSFC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), and D. M. Palmer (LANL) report on behalf of the Swift-BAT team: We perform further investigation regarding the uncertainty of the source nature of GRB151107A (Lien et al., GCN Circ. 18564) due to its proximity to the Galactic plane (within 1 deg) and the featureless light curve. Using analysis from the BAT transient monitor (Krimm et al., 2013), there is no significant emission in the 15-50 keV band at ~ 4000 s before and ~ 6000 s after the event data (signal-to-noise ratio < 1.8 sigma). The source was out of the field of view for the immediate time outside the event data range due to pre-planned telescope slews. A search in the daily mosaic images at the burst location shows a 4-sigma detection on Nov. 7 (12.5 mCrab) and 1.6 sigma on Nov. 8 (which corresponds to a 1-sigma upper limit of ~ 5 mCrab). This flux level and time profile are consistent with a GRB, and appear dimmer and shorter than a usual accreting binary source during outburst. However, we cannot rule out other possible Galactic transients, such as thermonuclear bursts or flaring stars. In addition, we note that within 20.3 arcsec of the revised BAT position is the bright M2/M3 type star designated HD 126577. It is possible that the BAT detections correspond to a flaring episode from HD 126577, although this star is not known for such episodes.