Observations and Theoretical Implications of GRB 970228

GRB 970228 is the first gamma ray burst for which prolonged post-bursttransient x-ray, optical, and infrared emission has been detected. RecentHubble Space Telescope observations show that the transient consists of twocomponents: a point source, which is known to be fading, and an extendedsource, which is possibly fading. I fit standard fireball remnant models to thefirst month of x-ray, optical, and infrared measurements, which may be donewithout assuming a GRB distance scale. I show that its emission is consistentwith that of the remnant of a relativistically expanding impulsive fireball inwhich a forward shock dominates the emission of the GRB event: the pistonmodel. However, two discrepant measurements may indicate that the post-burstflux varies by factors of approximately 3 on timescales of days or weeks.Furthermore, using the HST observations and the fitted model, I show that theextended object probably is fading, which may place GRB 970228 at galactic halodistances.Comment: Accepted to the Astrophysical Journal Letters, 11 pages, LaTe