L. Resmi

Detailed study of the GRB 030329 radio afterglow deep into the non-relativistic phase

Context. We explore the physics behind one of the brightest radio afterglows ever, GRB 030329, at late times when the jet is nonrelativistic. Aims. We determine the physical parameters of the blast wave and its surroundings, in particular the index of the electron energy distribution, the energy of the blast wave, and the density (structure) of the circumburst medium. We then compare our results with those from image size measurements. Methods. We observed the GRB 030329 radio afterglow with the Westerbork Synthesis Radio Telescope and the Giant Metrewave Radio Telescope at frequencies from 325 MHz to 8.4 GHz, spanning a time range of 268−1128 days after the burst. We modeled all the available radio data and derived the physical parameters. Results. The index of the electron energy distribution is p = 2.1, the circumburst medium is homogeneous, and the transition to the non-relativistic phase happens at tNR ∼ 80 days. The energy of the blast wave and density of the surrounding medium are comparable to previous findings. Conclusions. Our findings indicate that the blast wave is roughly spherical at tNR, and they agree with the implications from the VLBI studies of image size evolution. It is not clear from the presented dataset whether we have seen emission from the counter jet or not. We predict that the Low Frequency Array will be able to observe the afterglow of GRB 030329 and many other radio afterglows, constraining the physics of the blast wave during its non-relativistic phase even further.

Gamma Ray Burst reverse shock emission in early radio afterglows

Reverse shock (RS) emission from Gamma Ray Bursts is an important tool in investigating the nature of the ejecta from the central engine. If the ejecta magnetization is not high enough to suppress the RS, a strong RS emission component, usually peaking in the optical/IR band early on, would give important contribution to early afterglow light curves. In the radio band, synchrotron self-absorption may suppress early RS emission, and also delay the RS peak time. In this paper, we calculate the self-absorbed RS emission in the radio band for different dynamical conditions. In particular, we stress that the RS radio emission is subject to self-absorption in both reverse and forward shocks. We calculate the ratio between the reverse to forward shock flux at the RS peak time for different frequencies, which is a measure of the detectability of the RS emission component. We then constrain the range of physical parameters for a detectable RS, in particular the role of magnetization. We notice that unlike optical RS emission which is enhanced by moderate magnetization, a moderately magnetized ejecta does not necessarily produce a brighter radio RS due to the self-absorption effect. For typical parameters, the RS emission component would not be detectable below 1 GHz unless the medium density is very low (e.g.

Merger delay time distribution of extended emission short GRBs

n < 10^{-3} ~{\rm cm^{-3}}

Exploring Short-GRB afterglow parameter space for observations in coincidence with gravitational waves

for ISM and

Rates of short-GRB afterglows in association with binary neutron star mergers

A_* < 5\times 10^{-4}

Late-time evolution of afterglows from off-axis neutron star mergers

for wind). These predictions can be tested with the afterglow observations with current and upcoming radio facilities such as JVLA, LOFAR, FAST, and SKA.

Radio Afterglows of Gamma Ray Bursts

The most popular progenitor model for short duration Gamma-Ray bursts (sGRBs) is the merger of two compact objects. However, the short GRB population exhibit a certain diversity: some bursts display an extended emission (EE), continuing in soft

Explosive and Radio-Selected Transients: Transient Astronomy with Square Kilometre Array and its Precursors

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A comparative study of GRB-Supernovae

-rays for a few hundreds of seconds post the initial short pulse. It is currently unclear whether the origin of such bursts is linked to compact object mergers. Within the merger hypothesis, the redshift (

Radio, millimeter and optical monitoring of GRB 030329 afterglow: constraining the double jet model

z