Microlensing of collimated Gamma-Ray Burst afterglows

Abstract

We investigate stellar microlensing of the collimated gamma-ray burst afterglows. A spherical afterglow appears on the sky as a superluminally expanding thin ring (``ring-like'' image), which is maximally amplified as it crosses the lens. We find that the image of the collimated afterglow becomes quite uniform (``disk-like'' image) after the jet break time (after the Lorentz factor of the jet drops below the inverse of the jet opening angle). Consequently, the amplification peak in the light curve after the break time is lower and broader. Therefore detailed monitoring of the amplification history will be able to test whether the afterglows are jets or not, i.e., ``disk-like'' or not, if the lensing occurs after the break time. We also show that some proper motion and polarization is expected, peaking around the maximum amplification. The simultaneous detection of the proper motion and the polarization will strengthen that the brightening of the light curve is due to microlensing.

16 pages, 6 figures, accepted for publication in ApJ

References in corpus (4)

• Chromatic Signatures in the Microlensing of GRB Afterglows
• A Jet Model With a Hard Electron Distribution for the Afterglow of GRB 000301c
• Microlensing and the Surface Brightness Profile of the Afterglow Image of GRB 000301C
• Resolving the Image of Gamma-Ray Burst Afterglows with Gravitational Microlensing

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