A Distinct Peak-Flux Distribution of the Third Class of Gamma-Ray Bursts: A Possible Signature of X-Ray Flashes?

Vereš, P.; Bagoly, Z.; Horváth, I.; Mészáros, A.; Balázs, L. G.

doi:10.1088/0004-637x/725/2/1955

Cited by 61 publications

(80 citation statements)

References 39 publications

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“…This was confirmed from further analysis of the complete BATSE dataset (Horváth 2002;Chattopadhyay et al 2007;Zitouni et al 2015). Evidence for a third lognormal component was also found in Swift/BAT data (Horváth et al 2008;Huja et al 2009;Horváth et al 2010) using duration and also from two-dimensional clustering using both duration and hardness (Veres et al 2010 Horváth & Tóth (2016), who pointed that three lognormal distributions provide a better fit to the data than two with 99.9999% confidence level. Tarnopolski (2016a) finds that for the similar Swift GRB dataset consisting of 947 GRBs, three groups are favored in the observer frame, whereas two in the rest frame.…”

Section: Introductionsupporting

confidence: 63%

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Classification of gamma-ray burst durations using robust model-comparison techniques

Kulkarni

Desai

2017

Astrophys Space Sci

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Gamma-Ray Bursts (GRBs) have been conventionally bifurcated into two distinct categories dubbed "short" and "long", depending on whether their durations are less than or greater than two seconds respectively. However, many authors have pointed to the existence of a third class of GRBs with mean durations intermediate between the short and long GRBs. Here, we apply multiple model comparison techniques to verify these claims. For each category, we obtain the best-fit parameters by maximizing a likelihood function based on a weighted superposition of two (or three) lognormal distributions. We then do model-comparison between each of these hypotheses by comparing the chi-square probabilities, Akaike Information criterion (AIC), and Bayesian Information criterion (BIC). We uniformly apply these techniques to GRBs from Swift (both observer and intrinsic frame), BATSE, BeppoSAX, and Fermi-GBM. We find that the Swift GRB distributions (in the observer frame) for the entire dataset favor three categories at about 2.4σ from difference in chi-squares, and show decisive evidence in favor of three components using both AIC and BIC. However, when the same analysis is done for the subset of Swift GRBs with measured redshifts, two components are favored with marginal significance. For all the other datasets, evidence for three components is either very marginal or disfavored.

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Section: Introductionsupporting

confidence: 63%

“…Tarnopolski (2016a) finds that for the similar Swift GRB dataset consisting of 947 GRBs, three groups are favored in the observer frame, whereas two in the rest frame. The possible physical origin of the third intermediate class of Swift GRBs is attributed to X-ray flashes (Veres et al 2010).…”

Section: Introductionmentioning

confidence: 99%

Classification of gamma-ray burst durations using robust model-comparison techniques

Kulkarni

Desai

2017

Astrophys Space Sci

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“…A solution, proposed to deal with the classification ambiguity problem, was proposed and examined in a number of papers (Hakkila et al 2003;Horváth et al 2004Horváth et al , 2006Horváth et al , 2010Chattopadhyay et al 2007;Veres et al 2010). The idea is to examine a multi-dimensional space of various parameters; particularly, a two-dimensional space of the hardness ratio vs. duration T 90 .…”

Section: Discussionmentioning

confidence: 99%

On the limit between short and long GRBs

Tarnopolski

2015

Astrophys Space Sci

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Two classes of GRBs have been identified thus far without doubt and are prescribed to different physical scenarios-NS-NS or NS-BH mergers, and collapse of massive stars, for short and long GRBs, respectively. The existence of two distinct populations was inferred through a bimodal distribution of the observed durations T 90 , and the commonly applied 2 s limit between short and long GRBs was obtained by fitting a parabola between the two peaks in binned data from BATSE 1B. Herein, by means of a maximum likelihood (ML) method a mixture of two Gaussians is fitted to the datasets from BATSE, Swift, BeppoSAX, and Fermi in search for a local minimum that might serve as a new, more proper, limit for the two GRB classes. It is found that Swift and BeppoSAX distributions are unimodal, hence no local minimum is present, Fermi is consistent with the conventional limit, whereas BATSE gives the limit significantly longer (equal to 3.38 ± 0.27 s) than 2 s. These new values change the fractions of short and long GRBs in the samples examined, and imply that the observed T 90 durations are detector dependent, hence no universal limiting value may be applied to all satellites due to their different instrument specifications. Because of this, and due to the strong overlap of the two-Gaussian components, the straightforward association of short GRBs to mergers and long ones to collapsars is ambiguous.

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“…However, Mészáros et al (2000a,b); Litvin et al (2001); Bernui et al (2008); Veres et al (2010a); Ukwatta & Woźniak (2016) claimed different results. The pertinent intermediateduration GRBs (2 s T 90 10 s) (Mukherjee et al 1998;Horváth 1998;Balastegui et al 2001;Horváth 2002;Horváth et al 2008;Horváth 2009;Huja et al 2009;Řípa et al 2009;Horváth et al 2010;Veres et al 2010b;de Ugarte Postigo et al 2011;Řípa et al 2012;Zitouni et al 2015;Horváth & Tóth 2016;Řípa & Mészáros 2016;Yang et al 2016;Kulkarni & Desai 2017) were found to be distributed anisotropically on the sky (Mészáros et al 2000a,b;Litvin et al 2001;Vavrek et al 2008;Veres et al 2010a). However, Mészáros &Štoček (2003); Ukwatta & Woźniak (2016) claimed different results.…”

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confidence: 99%

Testing the Isotropic Universe Using the Gamma-Ray Burst Data of Fermi/GBM

Řípa

Shafieloo

2017

ApJ

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The sky distribution of Gamma-Ray Bursts (GRBs) has been intensively studied by various groups for more than two decades. Most of these studies test the isotropy of GRBs based on their sky number density distribution. In this work we propose an approach to test the isotropy of the Universe through inspecting the isotropy of the properties of GRBs such as their duration, fluences and peak fluxes at various energy bands and different time scales. We apply this method on the Fermi / Gamma-ray Burst Monitor (GBM) data sample containing 1591 GRBs. The most noticeable feature we found is near the Galactic coordinates l ≈ 30• , b ≈ 15• and radius r ≈ 20• − 40• . The inferred probability for the occurrence of such an anisotropic signal (in a random isotropic sample) is derived to be less than a percent in some of the tests while the other tests give results consistent with isotropy. These are based on the comparison of the results from the real data with the randomly shuffled data samples. Considering large number of statistics we used in this work (which some of them are correlated to each other) we can anticipate that the detected feature could be result of statistical fluctuations. Moreover, we noticed a considerably low number of GRBs in this particular patch which might be due to some instrumentation or observational effects that can consequently affect our statistics through some systematics. Further investigation is highly desirable in order clarify about this result, e.g. utilizing a larger future Fermi / GBM data sample as well as data samples of other GRB missions and also looking for possible systematics.

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A Distinct Peak-Flux Distribution of the Third Class of Gamma-Ray Bursts: A Possible Signature of X-Ray Flashes?

Cited by 61 publications

References 39 publications

Classification of gamma-ray burst durations using robust model-comparison techniques

Classification of gamma-ray burst durations using robust model-comparison techniques

On the limit between short and long GRBs

Testing the Isotropic Universe Using the Gamma-Ray Burst Data of Fermi/GBM

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