Power Law Decays in the Optical Counterparts of GRB 970228 and GRB970508

Abstract

We report on R_c and K band observations of the optical counterpart to GRB 970508 with the Fred Lawrence Whipple Observatory (FLWO) 1.2m telescope. Eleven R_c-band observations were obtained on 1997 May 12, and three on May14. The counterpart clearly faded between the two nights. On May 12 there was no evidence for variability (<9%) on 10-70 minute time scales based on 11 R_c-band observations. On May 19 a one hour observation set a limit on the K magnitude of K>18.2. Comparison of these data points with those obtained by other authors shows that the decay of the optical counterpart can be well fitted by a power law of the form f ~ t**-alpha where alpha = 1.22 +/- 0.03 with occasional fluctuations superposed. We note that the decay of the optical counterpart to another burst, GRB 970228, can also be well fitted with a power law with exponent alpha = 1.0/+0.2/-0.5 with occasional fluctuations superposed. These two decay light curves are remarkably similar in form to that predicted by cosmic-fireball models.

replacement, now accepted by ApJ(lett), 8 pages, 1 figure

References in corpus (8)

• Spectra and Light Curves of Gamma-Ray Burst Afterglows
• Viewing Angle and Environment Effects in GRB: Sources of Afterglow Diversity
• The Host Galaxy of GRB 970508
• The afterglow of gamma ray bursts II: the cases of GRB 970228 and GRB 970508
• Optical follow-up of GRB 970508
• Evidence for Diverse Optical Emission from Gamma-Ray Burst Sources
• The decay of optical emission from the Gamma-Ray Burst GRB 970228
• Multicolor photometry of the GRB970508 optical remnant

Cited by in corpus (22)

• The Dynamics and Light Curves of Beamed Gamma Ray Burst Afterglows
• A 450-day light curve of the radio afterglow of GRB 970508: Fireball calorimetry
• A Study of the Afterglows of Four GRBs: Constraining the Explosion and Fireball Model
• The Host Galaxy of GRB 970508
• On the energy of gamma-ray bursts
• Absorption in Gamma Ray Burst afterglows
• On the optical and X-ray afterglows of gamma ray bursts
• GRB 021004: a Massive Progenitor Star Surrounded by Shells
• Gamma-ray bursts: optical afterglows in the deep Newtonian phase
• The clustering of the luminosities of optical afterglows of long Gamma Ray Bursts
• Jets, Structured Outflows, and Energy Injection in GRB Afterglows: Numerical Modelling
• Phenomenology of Reverse-Shock Emission in the Optical Afterglows of Gamma Ray Bursts
• The Rapid Decay of the Optical Emission from GRB 980326 and its Possible Implications
• The Non-Relativistic Evolution of GRBs 980703 and 970508: Beaming-Independent Calorimetry
• The very red afterglow of GRB 000418 - further evidence for dust extinction in a GRB host galaxy
• On the radio afterglow of gamma ray bursts
• Gamma-ray bursts: afterglows from cylindrical jets
• Applying an accurate spherical model to gamma-ray burst afterglow observations
• Non-thermal high-energy emissions from black holes by a relativistic capillary effect
• No Radio Afterglow from the Gamma-Ray Burst of February 28, 1997
• Radio Observations of GRB Afterglows
• The GROND GRB sample: II. Fireball parameters for four GRB afterglows