Are GRB 980425 and GRB 031203 real outliers or twins of GRB 060218?

Abstract

GRB 980425 and GRB 031203 are apparently two outliers with respect to the correlation between the isotropic equivalent energy E_iso emitted in the prompt radiation phase and the peak frequency E_peak of the spectrum in a vF(v) representation (the so-called Amati relation). We discuss if these two bursts are really different from the others or if their location in the E_iso-E_peak plane is the result of other effects, such as viewing them off-axis, or through a scattering screen, or a misinterpretation of their spectral properties. The latter case seems particularly interesting after GRB 060218, that, unlike GRB 031203 and GRB 980425, had a prompt emission detected both in hard and soft X-rays which lasted ~2800 seconds. This allowed to determine its E_peak and total emitted energy. Although it shares with GRB 031203 the total energetics, it is not an outlier with respect to the Amati correlation. We then investigate if a hard-to-soft spectral evolution in GRB 031203 and GRB 980425, consistent with all the observed properties, can give rise to a time integrated spectrum with an E_peak consistent with the Amati relation.

13 pages, 9 figures, 2 tables. Accepted for publication in MNRAS

References in corpus (4)

• An optical supernova associated with the X-ray flash XRF 060218
• SN 2006aj and the nature of low-luminosity gamma-ray bursts
• Discovery of a tight correlation among the prompt emission properties of long Gamma Ray Bursts
• The soft X-ray blast in the apparently sub-luminous GRB 031203

Cited by in corpus (20)

• Discerning the physical origins of cosmological Gamma-ray bursts based on multiple observational criteria: the cases of z=6.7 GRB 080913, z=8.3 GRB 090423, and some short/hard GRBs
• A Complete Catalog of Swift GRB Spectra and Durations: Demise of a Physical Origin for Pre-Swift High-Energy Correlations
• A comprehensive analysis of Swift/XRT data: I. Apparent spectral evolution of GRB X-ray tails
• The Epeak-Eiso plane of long Gamma Ray Bursts and selection effects
• On the consistency of the peculiar GRBs 060218 and 060614 with the Ep,i - Eiso correlation
• Confirming the gamma-ray burst spectral-energy correlations in the era of multiple time breaks
• Neutrino Spectra from Low and High Luminosity Populations of Gamma Ray Bursts
• Peak energy of the prompt emission of long Gamma Ray Bursts vs their fluence and peak flux
• Nonthermal gamma-ray and X-ray flashes from shock breakout in gamma-ray bursts/supernovae
• Temporal Profiles and Spectral Lags of XRF 060218
• Did we observe the supernova shock breakout in GRB 060218?
• The nature of the X-Ray Flash of August 24 2005
• Black-body components in Gamma-Ray Bursts spectra?
• The updated spectral catalogue of INTEGRAL Gamma-Ray Bursts
• The low-luminosity tail of the GRB distribution: the case of GRB 980425
• Redshift Degeneracy in the Eiso-Epeak Relation of Gamma-Ray Bursts
• Broadband lightcurve characteristics of GRBs 980425 and 060218 and comparison with long-lag, wide-pulse GRBs
• Testing a new luminosity/redshift indicator for $\gamma$-ray bursts
• Probing the low-luminosity GRB population with new generation satellite detectors
• Two types of softening detected in X-ray afterglows of Swift bursts: internal and external shock origins?