| タイトル | A Jet Break in the X-ray Light Curve of Short GRB 111020A: Implications for Energetics and Rates |
| 本文（外部サイト） | http://hdl.handle.net/2060/20130012535 |
| 著者（英） | Zauderer, B. A.; Berger, E.; Fong, W.; Gehrels, N.; Margutti, R.; Chornock, R.; Troja, E.; Fox, D. B.; Czekala, I.; Sakamoto, T.; Podsiadlowski, P. |
| 著者所属（英） | NASA Goddard Space Flight Center |
| 発行日 | 2012-08-27 |
| 言語 | eng |
| 内容記述 | We present broadband 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 approx.100 s to 10 days after the burst, reveals a significant break at (delta)t approx. = 2 days with pre- and post-break decline rates of (alpha)X,1 approx. = -0.78 and (alpha)X,2 < or approx. 1.7, respectively. Interpreted as a jet break, we infer a collimated outflow with an opening angle of (theta)j approx. = 3deg - 8deg. The resulting beaming-corrected gamma-ray (10-1000 keV band) and blast-wave kinetic energies are (2-3) x 10(exp 48) erg and (0.3-2) x 10(exp 49) erg, respectively, with the range depending on the unknown redshift of the burst. We report a radio afterglow limit of <39 micro-Jy (3(sigma)) from Expanded Very Large Array observations that, along with our finding that v(sub c) < v(sub X), constrains the circumburst density to n(sub 0) approx.0.01 0.1/cu cm. Optical observations provide an afterglow limit of i > or approx.24.4 mag at 18 hr after the burst and reveal a potential host galaxy with i approx. = 24.3 mag. The subarcsecond localization from Chandra provides a precise offset of 0".80+/-0".11 (1(sigma))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) x 10(exp 21)/sq cm (z = 0). Our observations demonstrate that a growing fraction of short gamma-ray bursts (GRBs) are collimated, which may lead to a true event rate of > or approx.100-1000 Gpc(sup -3)/yr, in good agreement with the NS-NS merger rate of approx. = 200-3000 Gpc(sup -3)/ yr. This consistency is promising for coincident short GRB-gravitational wave searches in the forthcoming era of Advanced LIGO/VIRGO. |
| NASA分類 | Astronomy |
| レポートNO | GSFC-E-DAA-TN6804 |
| 権利 | Copyright, Distribution under U.S. Government purpose rights |
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