A Comprehensive Analysis of Swift XRT Data. III. Jet Break Candidates in X-Ray and Optical Afterglow Light Curves

By E. Liang, J. Racusin, Bing Zhang, Binbin Zhang, D. Burrows. 2007

185 citations recorded by the source corpus.

The Swift XRT data for 179 GRBs (050124 to 070129) and the optical afterglow data for 57 pre- and post-Swift GRBs are analyzed to explore whether the observed breaks in the afterglow light curves can be interpreted as jet breaks, as well as their implications for jet energetics. We find that no burst is included in our “Platinum” sample, in which the data fully satisfy the jet break criteria. By relaxing one or more of the requirements for a jet break, candidates to various degrees are identified. In the X-ray band, 42 of 103 well-sampled X-ray light curves have a decay slope ≳1.5 in the postbreak segment (the “Bronze” sample), and 27 of these also satisfy the closure relations of the forward-shock models (“Silver” sample). The numbers of “Bronze” and “Silver” candidates in the optical light curves are 27 and 23, respectively. The X-ray break time is earlier than that in the optical bands. Among 13 bursts having both optical and X-ray light curves, only seven have an achromatic break, and even in these cases, only in one band do the data satisfy the closure relations (“Gold” sample). These results raise concerns about interpreting the breaks as jet breaks and further inferring GRB energetics. Assuming that the “Silver” and “Gold” breaks are jet breaks, we derive jet opening angles (θj) and kinetic energies (EK) or lower limits on them and find that the EK distribution is much more scattered than the pre-Swift sample, but a tentative anticorrelation between θj and EK,iso is found, indicating that the EK could still be quasi-universal.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/9821ee52664827bc6612698caa1ad89b1dcdd42c

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In Astronomy and Astrophysics

1. Bing Zhang
2. Pawan Kumar
3. E. Berger
4. E. Nakar
5. B. Metzger
6. A. Tchekhovskoy
7. J. McKinney
8. E. Liang

Citations in the corpus

• THE AFTERGLOWS OF SWIFT-ERA GAMMA-RAY BURSTS. II. TYPE I GRB VERSUS TYPE II GRB OPTICAL AFTERGLOWS (2008, background): “…“superluminous” GRBs (e.g., GRB 050820A, GRB 050904 and GRB 070125, Cenko et al. 2006a; Tagliaferri et al. 2005; Frail et al. 2006; Chandra et al. 2008; Updike et al. 2008), the idea of a standard energy reservoir for Type II GRBs is untenable (see also Kocevski & Butler 2007; Liang et al. 2008).”
• CONSTRAINING GAMMA-RAY BURST INITIAL LORENTZ FACTOR WITH THE AFTERGLOW ONSET FEATURE AND DISCOVERY OF A TIGHT Γ0–Eγ,iso CORRELATION (2009, methodology): “The details of XRT data reduction have been presented in a series of papers published by our group (Zhang et al. 2007a, Paper I; Liang et al. 2007, 2008, 2009; Papers II, III, IV).”
• EFFICIENCY OF MAGNETIC TO KINETIC ENERGY CONVERSION IN A MONOPOLE MAGNETOSPHERE (2009, background): “The inferred total power of long GRBs is on the order of 1051 erg (Piran 2005; Meszaros 2006; Liang et al. 2008); however, much less energetic events, with total energy releas as low as 1048 erg, have also been observed (Soderberg et al. 2004, 2006).”
• JET BREAKS AND ENERGETICS OF Swift GAMMA-RAY BURST X-RAY AFTERGLOWS (2008, background): “Other large scale studies (Liang et al. 2008; Panaitescu 2007; Evans et al. 2008) of jet break closure relations address only the simplest cases of the uniform jet (Zhang & Mészáros 2004).”
• The prompt-afterglow connection in gamma-ray bursts: a comprehensive statistical analysis of Swift X-ray light curves (2012, background): “…observer frame properties and tried to understand to what extent the observations could be reconciled with the standard forward shock model (e.g. O’Brien et al. 2006; Butler 2007; Butler & Kocevski 2007; Willingale et al. 2007; Liang et al. 2007, 2008; Evans et al. 2009; Racusin et al. 2009, 2011).”
• The physics of gamma-ray bursts & relativistic jets (2014, background): “…− 1049 erg s−1, typically with long durations, soft spectra, and single-peaked smooth lightcurves) as a separate population, which has a distinct bump in the luminosity function, then it is found that α1 ∼ 0.5 for the high-luminosity GRB component (e.g. Liang et al., 2007a; Virgili et al., 2009).”
• A complete reference of the analytical synchrotron external shock models of gamma-ray bursts (2013, methodology): “Systematic data analyses (Zhang et al., 2007; Liang et al., 2007, 2008, 2009; Butler and Kocevski, 2007; Kocevski et al., 2007; Chincarini et al., 2007, 2010; Margutti et al., 2010) suggest that the X-ray afterglow is a superposition of the conventional external shock component and a radiation…”
• Magnetic acceleration of ultrarelativistic jets in gamma-ray burst sources (2008, background): “Recent observations by the Swift satellite have indicated that various aspects of this model may need to be modified (e.g. Mészáros 2006; Panaitescu 2007; Liang et al. 2008), but the basic picture of a collimated Γ>∼ 10 2 outflow is still the accepted paradigm.”
• AFTERGLOW OBSERVATIONS OF FERMI LARGE AREA TELESCOPE GAMMA-RAY BURSTS AND THE EMERGING CLASS OF HYPER-ENERGETIC EVENTS (2010, background): “Second, there has been a dearth of measurements of jet opening angles (e.g., Panaitescu 2007; Kocevski & Butler 2008; Liang et al. 2008; Racusin et al. 2009) and well-sampled multiwavelength GRB afterglows (used to derived the afterglow kinetic energy EKE).”
• DISCERNING THE PHYSICAL ORIGINS OF COSMOLOGICAL GAMMA-RAY BURSTS BASED ON MULTIPLE OBSERVATIONAL CRITERIA: THE CASES OF z = 6.7 GRB 080913, z = 8.2 GRB 090423, AND SOME SHORT/HARD GRBs (2009, background): “Recent Swift observations suggest that the “achromatic” behavior, the demanded characteristic of a jet break, is not commonly seen (Liang et al. 2008).”