Volume 556, August 2013
|Number of page(s)||9|
|Section||Stellar structure and evolution|
|Published online||19 July 2013|
X-ray, optical, and infrared investigation of the candidate supergiant fast X-ray transient IGR J18462 − 0223
1 INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, via Gobetti 101, 40129 Bologna, Italy
2 School of Physics and Astronomy, University of Southampton, University Road, Southampton, SO17 1BJ, UK
3 INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica, via E. Bassini 15, 20133 Milano, Italy
4 INAF, Istituto di Astrofisica e Planetologia Spaziali, via Fosso del Cavaliere 100, 00133 Rome, Italy
Received: 23 November 2012
Accepted: 6 May 2013
We report on a broad-band X-ray study (0.5–60 keV) of the poorly known candidate supergiant fast X-ray transient (SFXT) IGR J18462 − 0223, and on optical and near-infrared (NIR) followup observations of field objects. The out-of-outburst X-ray state has been investigated for the first time with archival INTEGRAL/IBIS, ASCA, Chandra, and Swift/XRT observations. This allowed us to place stringent 3σ upper limits on the soft (0.5–10 keV) and hard (18–60 keV) X-ray emission of 2.9 × 10-13 erg cm-2 s-1 and 8 × 10-12 erg cm-2 s-1, respectively. The source was also detected during an intermediate soft X-ray state with flux equal to 1.6 × 10-11 erg cm-2 s-1 (0.5–10 keV). In addition, we report on the INTEGRAL/IBIS discovery of three fast hard X-ray flares (18–60 keV) having a duration in the range 1–12 h and the flaring behavior was investigated in soft X-rays (3–10 keV) with archival INTEGRAL/JEM–X observations. The duty cycle (1.2%) and the dynamic ranges ( > 1380 and > 190 in the energy bands 0.5–10 keV and 18–60 keV, respectively) were measured for the first time. Archival UKIDSS JHK NIR data, together with our deep R-band imaging of the field, unveiled a single, very red object inside the intersection of the Swift/XRT and XMM-Newton error circles. This source has optical/NIR photometric properties compatible with a very heavily absorbed blue supergiant located at ~11 kpc, so is a strong candidate for a counterpart to IGR J18462 − 0223. NIR spectroscopy is advised to confirm the association. Finally, a hint of a possible orbital period was found at ~2.13 days. If confirmed by further studies, this would make IGR J18462 − 0223 the SFXT with the shortest orbital period among the currently known systems.
Key words: X-rays: binaries / X-rays: individuals: IGR J18462-0223
© ESO, 2013
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.