Konus-Wind observations of the new soft gamma-ray repeater SGR 0501+4516

TL;DR

This paper reports on the analysis of five short gamma-ray bursts from the newly discovered SGR 0501+4516, revealing typical SGR properties, spectral evolution, and high peak luminosities consistent with known SGRs.

Contribution

First detailed spectral and temporal analysis of bursts from SGR 0501+4516, confirming its classification as a typical SGR with characteristic burst properties.

Findings

Bursts are shorter than 0.75 seconds.

Spectra fit by optically-thin thermal bremsstrahlung with kT of 20-40 keV.

Peak luminosities are (2-5)×10^{40} erg/s, typical for short SGR bursts.

Abstract

In 2008 August, the new soft gamma-ray repeater SGR 0501+4516 was discovered by Swift. The source was soon confirmed by several groups in space- and ground-based multi-wavelength observations. In this letter we report the analysis of five short bursts from the recently discovered SGR, detected with Konus-Wind gamma-ray burst spectrometer. Properties of the time histories of the observed events, as well as results of multi-channel spectral analysis, both in the 20--300 keV energy range, show, that the source exhibits itself as a typical SGR. The bursts durations are <0.75 s and their spectra above 20 keV can be fitted by optically-thin thermal bremsstrahlung (OTTB) model with kT of 20--40 keV. The spectral evolution is observed, which resembles the SGR 1627-41 bursts, where a strong hardness-intensity correlation was noticed in the earlier Konus-Wind observations. The peak energy fluxes of all five events are comparable to highest those for known SGRs, so a less distant source is implied, consistent with the determined Galactic anti-center direction. Supposing the young supernova remnant HB9 (at the distance of 1.5 kpc) as a natal environment of the source, the peak luminosities of the bursts are estimated to be (2--5)x10^{40} erg s-1. The values of the total energy release, given the same assumptions, amount to (0.6--6)x10^{39} erg. These estimations of both parameters are typical for short SGR bursts.