GRB 070311: Optical follow-up

GCN Circular #6195 GRB 070311: MDM Optical Detection

J. P. Halpern & E. Armstrong (Columbia U.) report on behalf of the MDM Observatory GRB follow-up team. "We acquired R-band observations of INTEGRAL GRB 070311 (Mereghetti et al., GCN 6189) using the MDM 1.3m telescope on Mar. 11 02:44-03:28 UT. The IR afterglow discovered by Covino et al. (GCN 6190) and confirmed by Bloom (GCN 6191) is well detected in our images. In an uncalibrated image, we measure a preliminary magnitude of R = 21.12 +/- 0.09 at a mean time of 02:47 UT, or 54 minutes post-burst. This is with respect to a comparison star with USNO-B1.0 magnitude R2=16.67 at (J2000) 05:50:11.83, +03:22:25.2. This message may be cited"

(J2000) 05h 50m 08.21s, +03° 22′ 30.3″

MDM 1.3m R-band Mar. 11.12 UT

MDM 1.3m R-band Mar. 12.15 UT

MDM 1.3m R-band Mar. 13.13 UT

MDM 1.3m R-band Mar. 14.15 UT

MDM 1.3m R-band Mar. 15.14 UT

GCN Circular #6199 GRB 070311: MDM Optical Follow-up

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 for a second night using the MDM 1.3m telescope. A combined 8x600 s image with mid-epoch Mar. 12 03:33 UT yields R = 23.05 +/- 0.10 using the same comparison star as in GCN 6195. The corresponding power-law decay index is -0.53 between 0.9 and 25.7 hours. The seeing was ~1.7". There is possible evidence for emission extending ~1.5" to the west of the OT. If so, it may contribute to the shallow decay index. MDM images are posted at http://www.astro.columbia.edu/~jules/grb/070311/ This message may be cited"

GCN Circular #6203 GRB 070311: Optical Brightening

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"

GCN Circular #6208 GRB 070311: MDM Optical Monitoring

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 fourth and fifth consecutive nights using the MDM 1.3m telescope. The new results are summarized as follows (using the comparison star from GCN 6195): ----------------------------------------- Date(UT) t-t0(days) Exposure R(mag) +/- ----------------------------------------- Mar 14.15 3.07 7x600s 22.65 0.07 Mar 15.14 4.06 9x600s 23.62 0.13 ----------------------------------------- These magnitudes are in agreement with observations of Greco et al. (GCN 6204) and Kann, Filgas, & Hoegner GCN (6206), which together show that the rebrightening we reported in GCN 6203 peaked on day 2. The afterglow is now fading rapidly. The latest MDM images are posted at http://www.astro.columbia.edu/~jules/grb/070311/ This message may be cited"

Last Modified: March 15, 2007	jules@astro.columbia.edu