Weblog
14 Could 2025

NASA/Swift/Cruz deWilde
Gamma-ray bursts (GRBs) are essentially the most highly effective phenomena within the Universe. First detected in the course of the Chilly Battle, these occasions beam an incredible quantity of high-energy mild our means in a brief time period. They arrive in two sorts: quick GRBs that final for lower than two seconds and lengthy GRBs that final for minutes. Each sorts have mysterious origins. Quick GRBs could possibly be brought on by the collisions of neutron stars or maybe the highly effective flares of a magnetar. Observations of lengthy GRBs recommend they’re brought on by a strong supernova known as a hypernova, the place an enormous star collapses to turn out to be a black gap. However a brand new examine means that the origins of lengthy GRBs are extra numerous.
One of many challenges in explaining lengthy gamma-ray bursts is that they’ve a variety of behaviors. Some are much less vivid, whereas others are immensely highly effective. Some have lengthy afterglows of radio mild, whereas others have nearly no afterglows. The final thought to elucidate that is that essentially the most highly effective GRBs happen when a jet of the hypernova is pointed in our path. When the jet isn’t fairly aimed our means, the GRB may be fainter. The afterglows could possibly be defined by high-energy mild ionizing the encompassing interstellar medium. This new examine suggests this isn’t sufficient to elucidate the noticed vary of lengthy GRBs.
The authors base their argument on observations gathered by the Neil Gehrels Swift Observatory, which has noticed greater than 1,600 GRBs and has measured the redshifts of about 500 of them. From this information, the authors give attention to 280 GRBs for which Swift gathered good mild curve profiles. Because the mild curves of supernovae are effectively understood, hypernove mild curves may be modeled in the same means. We all know how hypernovae ought to brighten and fade over time. By evaluating this to the sunshine curves of the GRBs, the authors discover that solely about half of them are match to hypernovae. This means that lengthy GRBs don’t have a singular origin. The authors recommend that different phenomena, such because the mergers of black holes or a black gap merging with a neutron star or white dwarf, might clarify the range of noticed GRBs.
The group additionally notes that matching mild curves is difficult. There are assumptions it’s important to make when accounting for the consequences of redshift and observational bias. The Swift information isn’t detailed sufficient to utterly rule out one origin mannequin over the opposite in quite a few cases. However the information clearly means that the astrophysical processes creating GRBs are far more numerous than we’ve thought.