Open AccessNew soft gamma‐ray bursts in the BATSE records and spectral properties of X‐ray rich bursts
Author(s) -
Tikhomirova Yana,
Stern Boris E.,
Kozyreva Alexandra,
Poutanen Juri
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2006.10047.x
Subject(s) - physics , gamma ray burst , astrophysics , light curve , population , spectral line , transient (computer programming) , astronomy , demography , sociology , computer science , operating system
A population of X‐ray dominated gamma‐ray bursts (GRBs) observed by Ginga , BeppoSAX and the High Energy Transient Explorer (HETE‐2) should be represented in the Burst and Transient Source Experiment (BATSE) data as presumably soft bursts. We have performed a search for soft GRBs in the BATSE records in the 25–100 keV energy band. The softness of a burst spectrum could explain why it has been missed by the on‐board procedure and by the previous searches for untriggered GRBs tuned to the 50–300 keV range. We have found a surprisingly small number ( ∼ 20 yr −1 with fluxes down to 0.1 photon cm −2 s −1 ) of soft GRBs where the count rate is dominated by the 25–50 keV energy channel. This fact, as well as the analysis of HETE‐2 and common BeppoSAX /BATSE GRBs, indicates that the majority of GRBs with a low E peak have a relatively hard tail with a high‐energy power‐law photon index β > −3. An exponential cutoff in GRB spectra below 10–15 keV may be a distinguishing feature of non‐GRB events.