A UNIFIED PICTURE for LOW-LUMINOSITY and LONG GAMMA-RAY BURSTS BASED on the EXTENDED PROGENITOR of llGRB 060218/SN 2006AJ

Ehud Nakar*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

The relation between long gamma ray bursts (LGRBs) and low-luminosity GRBs (llGRBs) is a long standing puzzle - on one hand their high energy emission properties are fundamentally different, implying a different gamma ray source, yet both are associated with similar supernovae of the same peculiar type (broad-line Ic), pointing at a similar progenitor and a similar explosion mechanism. Here we analyze the multi-wavelength data of the particularly well-observed SN 2006aj, associated with llGRB 060218, finding that its progenitor star is sheathed in an extended (), low-mass () envelope. This progenitor structure implies that the gamma ray emission in this llGRB is generated by a mildly relativistic shock breakout. It also suggests a unified picture for llGRBs and LGRBs, where the key difference is the existence of an extended low-mass envelope in llGRBs and its absence in LGRBs. The same engine, which launches a relativistic jet, can drive the two explosions, but, while in LGRBs the ultra-relativistic jet emerges from the bare progenitor star and produces the observed gamma rays, in llGRBs the extended envelope smothers the jet and prevents the generation of a large gamma ray luminosity. Instead, the jet deposits all its energy in the envelope, driving a mildly relativistic shock that upon breakout produces a llGRB. In addition for giving a unified view of the two phenomena, this model provides a natural explanation to many observed properties of llGRBs. It also implies that llGRBs are a viable source of the observed extra-galactic diffuse neutrino flux and that they are promising sources for future gravitational wave detectors.

Original languageEnglish
Article number172
JournalAstrophysical Journal
Volume807
Issue number2
DOIs
StatePublished - 10 Jul 2015

Keywords

  • gamma ray burst: general
  • gamma ray burst: individual (GRB060218)
  • gravitational waves
  • neutrinos
  • supernovae: general
  • supernovae: individual (SN2006aj)

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