Issue |
A&A
Volume 468, Number 1, June II 2007
|
|
---|---|---|
Page(s) | L21 - L24 | |
Section | Letters | |
DOI | https://doi.org/10.1051/0004-6361:20077439 | |
Published online | 24 April 2007 |
Letter to the Editor
INTEGRAL high energy detection of the transient IGR J11321–5311
1
School of Physics and Astronomy, University of Southampton, Highfield, SO17 1BJ, UK e-mail: sguera@astro.soton.ac.uk
2
INAF/IASF Roma, via Fosso del Cavaliere 100, 00133 Roma, Italy
3
INAF/IASF Bologna, via Piero Gobetti 101, 40129 Bologna, Italy
Received:
8
March
2007
Accepted:
14
April
2007
Context.The transient hard X-ray source IGR J11321-5311 was discovered by INTEGRAL on June 2005, during observations of the Crux spiral arm. To date, this is the only detection of the source to be reported by any X/γ-ray mission.
Aims.To characterize the behaviour and hence the nature of the source through temporal and spectral IBIS analysis.
Methods.Detailed spectral and temporal analysis has been performed using standard INTEGRAL software OSA v.5.1.
Results.To date, IGR J11321-5311 has been detected only once. It was active for ~3.5 h, a short and bright flare lasting ~1.5 h is evident in the IBIS light curve. It reached a peak flux of ~80 mCrab or 2.2 10-9 erg cm-2 s-1 (20–300 keV), corresponding to a peak luminosity of ~1.1
1037 erg s-1 (assuming a distance of 6.5 kpc). During the outburst, the source was detected with a significance of ~18σ (20–300 keV) and ~8σ (100–300 keV). The spectrum of the total outburst activity (17–300 keV) is best fitted by the sum of a power law (Γ = 0.55 ± 0.18) plus a black body (kT = 1.0
keV), with no evidence for a break up to 300 keV. A spectral analysis at Science Window level revealed an evident hardening of the spectrum through the outburst. The IBIS data were searched for pulsations with no positive result.
Conclusions.The X-ray spectral shape and the flaring behaviour favour the hypothesis that IGR J11321-5311 is an Anomalous X-ray Pulsar, though a different nature can not be firmly rejected at the present stage.
Key words: gamma rays: observations / X-rays: general / X-rays: individuals: IGR J11321-5311 / X-rays: binaries / X-rays: bursts / gamma rays: theory
© ESO, 2007
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.