GCN Circular 6203
J. P. Halpern & E. Armstrong (Columbia U.) report on behalf of the MDM Observatory GRB follow-up team: "We observed the afterglow of INTEGRAL GRB 070311 in the R band on the third consecutive night using the MDM 1.3m telescope. A combined 7x600 s image with mid-epoch Mar. 13 03:10 UT shows that the OT has brightened by 0.88 mag since the previous night, reported in GCN 6199. We measure R = 22.17 +/- 0.06 at 49.3 hours post burst, using the same comparison star as in GCN 6195. Considering that this location suffers 2.0 magnitudes of Galactic extinction in the R band, it is possible that this burst is at low redshift, and that the brightening represents the onset of a supernova. Spectroscopy to determine its redshift and to search for a supernova are urged, as well as continued photometry. MDM images are posted at http://www.astro.columbia.edu/~jules/grb/070311/ This message may be cited."