Orphan afterglow

from Wikipedia, the free encyclopedia

A Orphan Afterglow (German about orphan afterglow ) describes an emission of optical to radio emission caused by a gamma ray burst , which is not directed precisely to the ground and its gamma radiation can not be observed.

Gamma ray bursts are bursts with high power in the range of hard gamma radiation that can be detected over extragalactic distances . They are interpreted as the result of a highly relativistic jet that only emits gamma radiation at a small solid angle of around 3 °. During part of the long gamma ray burst, afterglow could be observed in other areas of the electromagnetic spectrum from X-rays to radio radiation. This is interpreted as an interaction of the ejected particles with the interstellar matter around the location of the gamma ray burst, after the jet speed has already been strongly decelerated. The lower Lorentz factor also opens the angle of radiation and the low-energy electromagnetic radiation is also emitted in spatial directions that have not received any gamma radiation.

Theoretical models predict that for every Gamma Ray Burst 700 orphan afterglows should be observable in the sky. However, the afterglow around a gamma ray burst is easier to find, as the discovery of gamma radiation leads to observations in other areas of the electromagnetic spectrum. Orphan afterglows discovered so far can also be interpreted as dirty fireballs. A search for orphan afterglow in the vicinity of Ibc-type supernovae , which are suspected to be the cause of the long gamma ray bursts, has so far only shown non-relativistic interactions with circumstellar matter.

If orphan afterglows cannot be proven beyond doubt even with further surveys , this would call into question the previous hypotheses on the formation of gamma ray bursts by highly relativistic jets.

literature

  • G. Ghirlanda et al .: GRB orphan afterglows in present and future radio transient surveys . In: Astrophysics. Solar and Stellar Astrophysics . 2014, arxiv : 1402.6338v1 .
  • Damien Macpherson, DM Coward, MG Zadnik: The Potential for Detecting Gamma-Ray Burst Afterglows from Population III Stars with the Next Generation of Infrared Telescopes . In: Astrophysics. Solar and Stellar Astrophysics . 2013, arxiv : 1310.4940v1 .
  • James E. Rhoads: Dirty Fireballs and Orphan Afterglows: A Tale of Two Transients . In: Astrophysics. Solar and Stellar Astrophysics . 2003, arxiv : astro-ph / 0301011v1 .
  • Tomonori Totani, Alin Panaitescu: Orphan Afterglows of Collimated Gamma-Ray Bursts: Rate Predictions and Prospects for Detection . In: Astrophysics. Solar and Stellar Astrophysics . 2002, arxiv : astro-ph / 0204258v1 .
  • Ehud Nakar, Tsvi Piran, Jonathan Granot: The Detectability of Orphan Afterglows . In: Astrophysics. Solar and Stellar Astrophysics . 2002, arxiv : astro-ph / 0204203v4 .