Discovery of the Optical Transient of GRB 990308

Schaefer, Bradley E.; Snyder, J. A.; Hernandez, J.; Roscherr, B.; Deng, M.; Ellman, N.; Bailyn, C.; Rengstorf, A.; Smith, D.; Levine, A.; Barthelmy, S.; Butterworth, P.; Hurley, K.; Cline, T.; Meegan, C.; Kouveliotou, C.; Kippen, R. M.; Park, H.-S.; Williams, G. G.; Porrata, R.; Bionta, R.; Hartmann, D.; Band, D.; Frail, D.; Kulkarni, S.; Bloom, J.; Djorgovski, S.; Sadava, D.; Chaffee, F.; Harris, F.; Abad, C.; Adams, B.; Andrews, P.; Baltay, C.; Bongiovanni, A.; Briceno, C.; Bruzual, G.; Coppi, P.; della Prugna, F.; Dubuc, A.; Emmet, W.; Ferrin, I.; Fuenmayor, F.; Gebhard, M.; Herrera, D.; Honeycutt, K.; Magris, G.; Mateu, J.; Mufson, S.; Musser, J.; Naranjo, O.; Oemler, A.; Pacheco, R.; Paredes, G.; Rengel, M.; Romero, L.; Rosenzweig, P.; Sabbey, C.; Sánchez, Ge.; Sánchez, Gu.; Schenner, H.; Shin, J.; Sinnott, J.; Sofia, S.; Stock, J.; Suarez, J.; Telléria, D.; Vicente, B.; Vieira, K.; Vivas, K.
Bibliographical reference

The Astrophysical Journal, Volume 524, Issue 2, pp. L103-L106.

Advertised on:
10
1999
Number of authors
70
IAC number of authors
0
Citations
28
Refereed citations
23
Description
The optical transient of the faint gamma-ray burst GRB 990308 was detected by the QUEST camera on the Venezuelan 1 m Schmidt telescope starting 3.28 hr after the burst. Our photometry gives V=18.32+/-0.07, R=18.14+/-0.06, B=18.65+/-0.23, and R=18.22+/-0.05 for times ranging from 3.28 to 3.47 hr after the burst. The colors correspond to a spectral slope of close to f_ν~ν^1/3. Within the standard synchrotron fireball model, this requires that the external medium be less dense than 10^4 cm^-3, the electrons contain more than 20% of the shock energy, and the magnetic field energy be less than 24% of the energy in the electrons for normal interstellar or circumstellar densities. We also report upper limits of V>12.0 at 132 s (with LOTIS), V>13.4 from 132 to 1029 s (with LOTIS), V>15.3 at 28.2 minutes (with Super-LOTIS), and a 8.5 GHz flux of less than 114 μJy at 110 days (with the Very Large Array). Wisconsin-Indiana-Yale-NOAO 3.5 m and Keck 10 m telescopes reveal this location to be empty of any host galaxy to R>25.7 and K>23.3. The lack of a host galaxy likely implies that it is either substantially subluminous or more distant than a redshift of ~1.2.