SUB-PHOTOSPHERIC EMISSION FROM RELATIVISTIC RADIATION MEDIATED SHOCKS IN GRBs

Journal Article · Wed Jun 01 04:00:00 EDT 2011 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/733/2/85· OSTI ID:21576751

Bromberg, Omer ^[1]; Mikolitzky, Ziv; Levinson, Amir ^[2]

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1. Racah Institute of Physics, Hebrew University, 91904 Jerusalem (Israel)
2. Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv University, 69978 Tel Aviv (Israel)

It is proposed that the prompt emission observed in bursts that exhibit a thermal component originates from relativistic radiation mediated shocks (RRMS) that form below the photosphere of the gamma-ray burst (GRB) outflow. It is argued that such shocks are expected to form in luminous bursts via collisions of shells that propagate with moderate Lorentz factors {Gamma} {approx}< 500. Faster shells will collide above the photosphere to form collisionless shocks. We demonstrate that in events like GRB 090902B a substantial fraction of the explosion energy is dissipated below the photosphere, in a region of moderate optical depth {tau} {approx}< 300, whereas in GRB 080916C the major fraction of the energy dissipates above the photosphere. We show that under conditions anticipated in many GRBs, such RRMS convect enough radiation upstream to render photon production in the shock transition negligible, unlike the case of shock breakout in supernovae. The resulting spectrum, as measured in the shock frame, has a relatively low thermal peak, followed by a broad, nonthermal component extending up to the Klein-Nishina limit.

• OSTI ID: 21576751
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 733; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ATMOSPHERES
COSMIC GAMMA BURSTS
COSMIC RADIATION
EMISSION
ENERGY TRANSFER
HEAT TRANSFER
IONIZING RADIATIONS
PHOTOSPHERE
PRIMARY COSMIC RADIATION
RADIANT HEAT TRANSFER
RADIATIONS
SHOCK WAVES
SOLAR ATMOSPHERE
STELLAR ATMOSPHERES