Xiang-Gao Wang

A CORRELATED STUDY OF OPTICAL AND X-RAY AFTERGLOWS OF GRBs

We study an extensive sample of 87 gamma-ray bursts (GRBs) for which there are well-sampled and simultaneous optical and X-ray light curves. We extract the cleanest possible signal of the afterglow component. and compare the temporal behaviors of the X-ray light. curve, observed by Swift XRT, and optical data, observed by UVOT and ground-based telescopes for each individual burst. Overall we find that 62% of the GRBs. are consistent with the standard afterglow model. When more advanced modeling is invoked, up to 91% of the bursts in our sample may be consistent with the external-shock model. A large fraction of these bursts are consistent with occurring in a constant interstellar density medium (61%) while only 39% of them occur in a wind-like medium. Only nine cases have afterglow light curves that exactly match the standard fireball model prediction, having a single power-law decay in both energy bands that are observed during their entire duration. In particular, for the bursts with chromatic behavior, additional model assumptions must be made over limited segments of the light curves in order for these bursts to fully agree with the external-shock model. Interestingly, for 54% of the X-ray and 40% of the optical band observations, the end of the shallow decay (t(similar to-0.5)) period coincides with the jet-break (t(similar to-p)) time, causing an abrupt change in decay slope. The fraction of the burst that is consistent with the external-shock model is independent of the observational epochs in the rest frame of GRBs. Moreover, no cases can be explained by the cooling frequency crossing the X-ray or optical band.

COSMIC EVOLUTION OF LONG GAMMA-RAY BURST LUMINOSITY

The cosmic evolution of gamma-ray burst (GRB) luminosity is essential for revealing the GRB physics and for using GRBs as cosmological probes. We investigate the luminosity evolution of long GRBs with a large sample of 258 {\em Swift}/BAT GRBs. Parameterized the peak luminosity of individual GRBs evolves as

HOW BAD OR GOOD ARE THE EXTERNAL FORWARD SHOCK AFTERGLOW MODELS OF GAMMA-RAY BURSTS?

L_{\rm p}\propto{\rm }(1+z)^{k}

How Bad/Good Are the External Forward Shock Afterglow Models of Gamma-Ray Bursts?

, we get

Gamma-Ray Burst Jet Breaks Revisited

k=1.49\pm0.19

Steep Decay Phase Shaped by the Curvature Effect. II. Spectral Evolution

using the non-parametric

Steep Decay Phase Shaped by the Curvature Effect. I. Flux Evolution

\tau

The Three-parameter Correlations About the Optical Plateaus of Gamma-Ray Bursts

statistics method without considering observational biases of GRB trigger and redshift measurement. By modeling these biases with the observed peak flux and characterizing the peak luminosity function of long GRBs as a smoothly broken power-law with a break that evolves as

First Electromagnetic Pulse Associated with a Gravitational-wave Event: Profile, Duration, and Delay

L_{\rm b}\propto (1+z)^{k_{\rm b}}

A Comprehensive Analysis of Fermi Gamma-Ray Burst Data. IV. Spectral Lag and its Relation to E p Evolution

, we obtain