Pre-ALMA observations of GRBs in the mm/submm range

Abstract

Context. Gamma-ray bursts (GRBs) generate an afterglow emission that can be detected from radio to X-rays during days, or even weeks after the initial explosion. The peak of this emission crosses the millimeter and submillimeter range during the first hours to days, making their study in this range crucial for constraining the models. Observations have been limited until now due to the low sensitivity of the observatories in this range. This situation will be greatly improved with the start of scientific operations of the Atacama Large Millimeter/submillimeter Array (ALMA). Aims. In this work we do a statistical analysis of the complete sample of mm/submm observations of GRB afterglows obtained before the beginning of scientific operations at ALMA. Methods. We present observations of 11 GRB afterglows obtained from the Atacama Pathfinder Experiment (APEX) and the SubMillimeter Array (SMA), as well as the first detection of a GRB with ALMA, still in the commissioning phase, and put them into context with a catalogue of all the observations that have been published until now in the spectral range that is covered by ALMA.Results. The catalogue of mm/submm observations collected here is the largest to date and is composed of 102 GRBs, of which 88 have afterglow observations, whereas the rest are host galaxy searches. With our programmes, we contributed with data of 11 GRBs and the discovery of 2 submm counterparts. In total, the full sample, including data from the literature, has 22 afterglow detections with redshifts ranging from 0.168 to 8.2. GRBs have been detected in mm/submm wavelengths with peak luminosities spanning 2.5 orders of magnitude, the most luminous reaching 10 33 erg s −1 Hz −1 . We observe a correlation between the X-ray brightness at 0.5 days and the mm/submm peak brightness. Finally we give a rough estimate of the distribution of peak flux densities of GRB afterglows, based on the current mm/submm sample. Conclusions. Observations in the mm/submm bands have been shown to be crucial for our understanding of the physics of GRBs, but have until now been limited by the sensitivity of the observatories. With the start of the operations at ALMA, the sensitivity has improved by more than an order of magnitude, opening a new era in the study of GRB afterglows and their host galaxies. Our estimates predict that, once completed, ALMA will detect up to ∼98% of the afterglows if observed during the passage of the peak synchrotron emission.

AT2018cow: A Luminous Millimeter Transient

“…have well-sampled, multifrequency light curves to date. This sample includes supernovae (SNe; Weiler et al 2007;Horesh et al 2013), tidal-disruption events (TDEs; Zauderer et al 2011;Yuan et al 2016) and gamma-ray bursts (GRBs; de Ugarte Postigo et al 2012;Laskar et al 2013;Perley et al 2014;Urata et al 2014).…”

First ALMA Light Curve Constrains Refreshed Reverse Shocks and Jet Magnetization in GRB 161219B

“…In one case, our observations were incompatible with RS radiation from the injection, suggesting that collisions in at least some instances may be gentle processes; for the remaining three cases, the observations lacked the requisite temporal sampling and frequency coverage to conclusively rule out an injection RS. The reason may partly stem from the fact that the RS emission peaks in the millimeter band for typical shock parameters, and no facilities in this observing window had the requisite sensitivity (de Ugarte Postigo et al 2012). However, the advent of the Atacama Large Millimeter/submillimeter Array (ALMA) now allows us to track the millimeter-band evolution of afterglows to a sensitivity of ∼30-100 μJy for the first time, reenergizing the search for refreshed RSs.…”

The Arcminute Microkelvin Imager catalogue of gamma-ray burst afterglows at 15.7 GHz

“…The first detection of a gamma-ray burst (GRB) at radio wavelengths (GRB 970508; Galama et al 1998;Frail et al 2000b), bought about a new era of transient astrophysics that has lead to over twenty years of discovery Chandra & Frail 2012;de Ugarte Postigo et al 2012). With the launch of Swift in 2004, the improved ability to localise GRBs to within 4 (Krimm et al 2013) using the Burst Alert Telescope (BAT; Barthelmy et al 2005), with more precise localisation being provided by the Swift X-ray Telescope (XRT; Burrows et al 2000) and the Swift Ultraviolet/Optical Telescope (UVOT; Roming et al 2005), has allowed back into the relativistic ejecta causing a much faster flash of emission .…”