A Jet Break in the X-Ray Light Curve of Short Grb 111020a: Implications for Energetics and Rates
Fox, D. B.
Podsiadlowski, P.Note: Order does not necessarily reflect citation order of authors.
MetadataShow full item record
CitationFong, W., E. Berger, R. Margutti, B. A. Zauderer, E. Troja, I. Czekala, R. Chornock, et al. 2012. A Jet Break in the X-Ray Light Curve of Short Grb 111020a: Implications for Energetics and Rates. The Astrophysical Journal 756, no. 2: 189. doi:10.1088/0004-637x/756/2/189.
AbstractWe present broad-band observations of the afterglow and environment of the short GRB 111020A. An extensive X-ray light curve from Swift/XRT, XMM-Newton and Chandra, spanning ∼ 100 seconds to 10 days after the burst, reveals a significant break at δt ≈2 days with pre- and post-break decline rates of αX,1 ≈ −0.78 and αX,2 . −1.7, respectively. Interpreted as a jet break, we infer a collimated outflow with an opening angle of θj ≈ 3 − 8◦. The resulting beaming-corrected γ-ray (10 − 1000 keV band) and blastwave kinetic energies are (2−3)×1048 erg and (0.3−2)×1049 erg, respectively, with the range depending on the unknown redshift of the burst. We report a radio afterglow limit of <39 µJy (3σ) from EVLA observations which, along with our finding that νc < νX , constrains the circumburst density to n0 ∼ 0.01 − 0.1 cm−3. Optical observations provide an afterglow limit of i & 24.4 mag at 18 hours after the burst, and reveal a potential host galaxy with i ≈ 24.3 mag. The sub-arcsecond localization from Chandra provides a precise offset of 0.80′′ ±0.11′′ (1σ) from this galaxy corresponding to an offset of 5−7 kpc for z = 0.5−1.5. We find a high excess neutral Hydrogen column density of (7.5 ± 2.0) × 1021 cm−2 (z = 0). Our observations demonstrate that a growing fraction of short GRBs are collimated which may lead to a true event rate of & 100 − 1000 Gpc−3 yr−1, in good agreement with the NS-NS merger rate of ≈ 200 − 3000 Gpc−3 yr−1. This consistency is promising for coincident short GRB-gravitational wave searches in the forthcoming era of Advanced LIGO/VIRGO.
Citable link to this pagehttp://nrs.harvard.edu/urn-3:HUL.InstRepos:30410846
- FAS Scholarly Articles 
Contact administrator regarding this item (to report mistakes or request changes)