1998/10/06 by Rosalba Perna, Abraham Loeb · 5 citations
Physics and Astronomy · #Active galactic nucleus #Afterglow #Astronomy #Astrophysical jet #Astrophysics #Astrophysics and Cosmic Phenomena #Galaxy #Gamma ray #Gamma-ray burst #Gamma-ray bursts and supernovae #Physics #Pulsars and Gravitational Waves Research #Sky #astro-ph
paper · pdf · doi:10.1086/311784
12 pages, 3 figures, submitted to ApJ
arxiv created 1998/10/06 · openalex publication_date 1998/12/20 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The degree of beaming in gamma-ray bursts (GRBs) is currently unknown. The uncertainty in the γ-ray-beaming angle, θ b , leaves the total energy release ( ∝ θ 2 b ) and the event rate per galaxy ( ∝ θ −2 b ) unknown to within orders of magnitude. Since the delayed radio emission of GRB sources originates from a mildly relativistic shock and receives only weak relativistic beaming, the rate of radio-selected transients with no GRB counterparts can be used to set an upper limit on θ −2 b . We find that a VLA survey with a sensitivity of ~0.1 mJy at 10 GHz could identify ≳2 × 10 4 (θ b /10°) −2 radio afterglows across the sky if each source is sampled at least twice over a period of 1 month or longer. From the total number of ≳0.1 mJy sources observed at 8.44 GHz and the fraction of fading sources at 1.44 GHz, we get the crude limit θ b ≳ 6°.