A Millimeter Rebrightening in GRB 210702A

Simon de Wet, Tanmoy Laskar, Paul J. Groot, Rodolfo Barniol Duran, Edo Berger, Shivani Bhandari, Tarraneh Eftekhari, Cristiano Guidorzi, Shiho Kobayashi, Daniel A. Perley, Re’em Sari, Genevieve Schroeder

Research output: Contribution to journalArticlepeer-review

Abstract

We present X-ray to radio frequency observations of the bright long gamma-ray burst GRB 210702A. Our Atacama Large Millimeter/submillimeter Array 97.5 GHz observations show a significant rebrightening by a factor of ≈2 beginning at 8.2 days post-burst and rising to peak brightness at 18.1 days before declining again. This is the first such rebrightening seen in a millimeter afterglow light curve. A standard forward shock model in a stellar wind circumburst medium can explain most of our X-ray, optical, and millimeter observations prior to the rebrightening, but significantly overpredicts the self-absorbed radio emission, and cannot explain the millimeter rebrightening. We investigate possible explanations for the millimeter rebrightening, and find that energy injection or a reverse shock from a late-time shell collision are plausible causes. Similar to other bursts, our radio data may require alternative scenarios such as a thermal electron population or a structured jet to explain the data. Our observations demonstrate that millimeter light curves can exhibit some of the rich features more commonly seen in optical and X-ray afterglow light curves, motivating further millimeter wavelength studies of GRB afterglows.

Original languageEnglish
Article number279
JournalAstrophysical Journal
Volume974
Issue number2
DOIs
StatePublished - 1 Oct 2024

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this