Statistical Distributions of Optical Flares from Gamma-Ray Bursts

Abstract

We statistically study gamma-ray burst (GRB) optical flares from the Swift/UVOT catalog. We compile 119 optical flares, including 77 flares with redshift measurements. Some tight correlations among the time scales of optical flares are found. For example, the rise time is correlated with the decay time, and the duration time is correlated with the peak time of optical flares. These two tight correlations indicate that longer rise times are associated with longer decay times of optical flares, and also suggest that broader optical flares peak at later times, which are consistent with the corresponding correlations of X-ray flares. We also study the frequency distributions of optical flare parameters, including the duration time, rise time, decay time, peak time and waiting time. Similar power-law distributions for optical and X-ray flares are found. Our statistic results imply that GRB optical flares and X-ray flares may share the similar physical origin and both of them are possibly related to central engine activities.

Self-organized Criticality in Multi-pulse Gamma-Ray Bursts

“…By analyzing the temporal properties (i.e., E iso , T and P ) of these pulses, we presented that the differential and the cumulative thresholded differential distributions of GRB temporal properties could be well understood within the physical framework of a fractal-diffusive, selforganized criticality (FD-SOC) model, which is generally consistent with the previous works on the SOC behavior in GRB X-ray flares [21,22,25,26]. However, the statistical results favor a spatial dimension of S = 3 of the SOC system for prompt properties, rather than a spatial dimension of S = 1 for the case of X-ray flares [21].…”

“…To summarize, we draw a tentative conclusion that our statistical results are explained in the theoretical prediction of a self-organized criticality system with the classical diffusion, the spatial dimension S = 3, which are generally consistent with statistical results of various black hole systems including GRBs, TDE Swift J1644+57, Sgr A * , M87. They can be explained by a three-dimensional SOC model [22], despite the dimension of our result is different from that of previous work [21,22,25,26], which implies that the relativistic jets may be magnetically dominated, consistent with our previous work [48].…”

“…However, Yi et al [25] comprehensively studied GRB X-ray flares observed by the Swift satellite, and their results supported the SOC phenomena in GRBs. Moreover, it is found that these statistical properties are similar to those of the X-ray flares, which indicates that GRB optical flares and X-ray flares may share a common physical origin [26]. Besides, the power density spectra (PDSs) of GRB prompt lightcurves (with a power-law index value of ∼ −5/3) indicate the bursts themselves have a self-similar temporal structure [27].…”

Constraining Properties of GRB Central Engines with X-ray flares

“…The X-ray flares usually happen at 10 2 − 10 5 s after the prompt emission, the temporal behavior and spectral properties of flares are similar to that of prompt emissions. Therefore, X-ray flares may share a similar physical origin as the prompt emission of GRBs (Burrows et al 2005b;Falcone et al 2006Falcone et al , 2007Liang et al 2006;Nousek et al 2006;Zhang et al 2006;Chincarini et al 2007Chincarini et al , 2010Abdo et al 2011;Wang & Dai 2013;Qin et al 2013;Troja et al 2015;Yi et al 2015Yi et al , 2016Yi et al , 2017aMu et al 2016a;Mu et al 2016b). The observations of X-ray flares could provide an important clue to understand the central engine of GRBs.…”

Testing Blandford-Znajek mechanism in black hole hyperaccretion flows for long-duration gamma-ray bursts

“…Our understanding of GRBs has been greatly improved since 1997, and according to the fireball shell model, the broadband afterglow emissions are from the external shock emission as the interaction of an ultra-relativistic ejecta with the circumburst medium (e.g., Mészáros & Rees 1997;Sari 1998;Wu et al 2003;Zou et al 2005;Yi et al 2013). Lots of multi-wavelength afterglows have been collected, and some different emission features have been found in the multiwavelength afterglows after the launch of Swift, such as, the five components in the canonical X-ray lightcurves, including several power-law decay phases and the erratic X-ray flares (e.g., Nousek et al 2006;Burrows et al 2005;Falcone et al 2006Falcone et al , 2007Liang et al 2006;Chincarini et al 2007Chincarini et al , 2010Abdo et al 2011;Troja et al 2015;Yi et al 2015Yi et al , 2016Yi et al , 2017aSi et al 2018), and some smooth onset bump, sharp reverse shock emission or supernovae component in the optical lightcurves (e.g., Liang et al 2010Liang et al , 2013Japelj et al 2014;Gao et al 2015;Zhou et al 2020). However, compared with the GRB afterglow emission, the physical origin of the GRB prompt emission is still less clear, even though the widely discussed scenario is the internal shock model (e.g., Piran 2004;Zhang 2007;Kumar & Zhang 2015).…”