The First Short GRB Millimeter Afterglow: The Wide-angled Jet of the Extremely Energetic SGRB 211106A
Abstract
We present the discovery of the first millimeter afterglow of a short-duration γ-ray burst (SGRB) and the first confirmed afterglow of an SGRB localized by the GUANO system on Swift. Our Atacama Large Millimeter/Sub-millimeter Array (ALMA) detection of SGRB 211106A establishes an origin in a faint host galaxy detected in Hubble Space Telescope imaging at 0.7 ≲ z ≲ 1.4. From the lack of a detectable optical afterglow, coupled with the bright millimeter counterpart, we infer a high extinction, A V ≳ 2.6 mag along the line of sight, making this one of the most highly dust-extincted SGRBs known to date. The millimeter-band light curve captures the passage of the synchrotron peak from the afterglow forward shock and reveals a jet break at {t}_{\mathrm{jet}}={29.2}_{-4.0}^{+4.5}$ days. For a presumed redshift of z = 1, we infer an opening angle, θ jet = (15.°5 ± 1.°4), and beaming-corrected kinetic energy of \mathrm{log}({E}_{{\rm{K}}}/\mathrm{erg})=51.8\pm 0.3$ , making this one of the widest and most energetic SGRB jets known to date. Combining all published millimeter-band upper limits in conjunction with the energetics for a large sample of SGRBs, we find that energetic outflows in high-density environments are more likely to have detectable millimeter counterparts. Concerted afterglow searches with ALMA should yield detection fractions of 24%-40% on timescales of ≳2 days at rates of ≈0.8-1.6 per year, outpacing the historical discovery rate of SGRB centimeter-band afterglows.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 2022
- DOI:
- 10.3847/2041-8213/ac8421
- arXiv:
- arXiv:2205.03419
- Bibcode:
- 2022ApJ...935L..11L
- Keywords:
-
- Gamma-ray bursts;
- Astronomy data modeling;
- Radio astronomy;
- Millimeter astronomy;
- Time domain astronomy;
- Relativistic jets;
- High energy astrophysics;
- 629;
- 1859;
- 1338;
- 1061;
- 2109;
- 1390;
- 739;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 20 pages, 9 figures, 4 tables. Version accepted for publication in ApJ Letters