2001/12/31 by Arieh Königl, Arieh Konigl, Jonathan Granot · 62 citations
Physics and Astronomy · #Afterglow #Astronomy #Astrophysics #Astrophysics and Cosmic Phenomena #Bubble #Galaxy #Gamma-ray burst #Gamma-ray bursts and supernovae #Interstellar medium #Millisecond pulsar #Neutron star #Nuclear physics #Physics #Pulsar #Pulsars and Gravitational Waves Research #Supernova #Supernova remnant #Synchrotron radiation #Vela #astro-ph
paper · pdf · doi:10.1086/340941
published in The Astrophysical Journal 574(1), 134-154 (IOP Publishing) · expanded version with new figures, 46 pages, 5 figures, to appear in ApJ (Vol. 574, July 20, 2002 issue)
arxiv created 2002/04/05 · openalex publication_date 2002/07/20 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
We propose to identify pulsar-wind bubbles (PWBs) as the environment in which the afterglow emission in at least some gamma-ray burst (GRB) sources originates. Such bubbles could naturally account for both the high fraction of the internal energy residing in relativistic electrons and positrons ( e ) and the high magnetic-to-internal energy ratio ( B ) that have been inferred in a number of sources from an interpretation of the afterglow emission as synchrotron radiation. GRBs might occur within PWBs under a number of scenarios: in particular, in the supranova model of GRB formation a prolonged (months to years) period of intense pulsar-type wind from the GRB progenitor precedes the burst. Focusing on this scenario, we construct a simple model of the early-time structure of a plerionic supernova remnant (SNR), guided by recent results on the Crab and Vela SNRs. The model is based on the assumption of an "equipartition" upper bound on the electromagnetic-to-thermal pressure ratio in the bubble and takes into account synchrotron-radiation cooling. We argue that the effective upstream hydrogen number density for a relativistic shock propagating into the bubble is given by n H,equiv = [4 p + ( B ' + ') 2 /4π]/ m p c 2 , where B ' and ' are, respectively, the comoving magnetic and electric fields, and p is the particle pressure. We show that, for plausible parameter values, n H,equiv spans the range inferred from spectral fits to GRB afterglows and that its radial profile varies within the bubble and may resemble a uniform interstellar medium, a stellar wind, or a molecular cloud. We consider how the standard expressions for the characteristic synchrotron spectral quantities are modified when the afterglow-emitting shock propagates inside a PWB instead of in a uniform interstellar medium and demonstrate that the predictions for the empirically inferred values of e and B are consistent with the observations. Finally, we outline a self-consistent interpretation of the X-ray emission features detected in sources such as GRB 991216 in the context of the supranova/PWB picture.