GRB 991216 Joins the Jet Set: Discovery and Monitoring of its Optical Afterglow

Details GRB 991216 Joins the Jet Set: Discovery and Monitoring of its Optical Afterglow GRB 991216 Joins the Jet Set: Discovery and Monitoring of its Optical Afterglow

2000-06-15

arxiv.org/abs/astro-ph/0006206v1

Astronomy and Astrophysics

Astrophysics

19 pages, accepted by The Astrophysical Journal

Scientific paper

10.1086/317134

The optical light curve of the energetic gamma-ray burst GRB 991216 is consistent with jet-like behavior in which a power-law decay steepens from t**(-1.22 +/- 0.04) at early times to t**(-1.53 +/- 0.05) in a gradual transition at around 2 d. The derivation of the late-time decay slope takes into account the constant contribution of a host or intervening galaxy which was measured 110 d after the event at R = 24.56 +/- 0.14, although the light curve deviates from a single power law whether or not a constant term is included. The early-time spectral energy distribution of the afterglow can be described as F_nu ~ nu**(-0.74 +/- 0.05) or flatter between optical and X-ray, which, together with the slow initial decay, is characteristic of standard adiabatic evolution in a uniformly dense medium. Assuming that a reported absorption-line redshift of 1.02 is correct, the apparent isotropic energy of 6.7 x 10**53 erg is reduced by a factor of ~ 200 in the jet model, and the initial half-opening angle is ~ 6 deg. GRB 991216 is the third good example of a jet-like afterglow (following GRB 990123 and GRB 990510), supporting a trend in which the apparently most energetic gamma-ray events have the narrowest collimation and a uniform ISM environment. This, plus the absence of evidence for supernovae associated with jet-like afterglows, suggests that these events may originate from a progenitor in which angular momentum plays an important role but a massive stellar envelope or wind does not, e.g., the coalescence of a compact binary.

Affiliated with

Also associated with

No associations

Rating

GRB 991216 Joins the Jet Set: Discovery and Monitoring of its Optical Afterglow does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with GRB 991216 Joins the Jet Set: Discovery and Monitoring of its Optical Afterglow, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and GRB 991216 Joins the Jet Set: Discovery and Monitoring of its Optical Afterglow will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-546875