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arXiv · 1610.02648

Multi-wavelength observations of IGR J17544-2619 from quiescence to outburst

E. Bozzo·V. Bhalerao·P. Pradhan·J. Tomsick·P. Romano·C. Ferrigno·S. Chaty·L. Oskinova·A. Manousakis·R. Walter·M. Falanga·S. Campana·L. Stella·M. Ramolla·R. Chini
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Abstract

In this paper we report on a long multi-wavelength observational campaign of the supergiant fast X-ray transient prototype IGR J17544-2619. A 150 ks-long observation was carried out simultaneously with XMM-Newton and NuSTAR, catching the source in an initial faint X-ray state and then undergoing a bright X-ray outburst lasting about 7 ks. We studied the spectral variability during outburst and quiescence by using a thermal and bulk Comptonization model that is typically adopted to describe the X-ray spectral energy distribution of young pulsars in high mass X-ray binaries. Although the statistics of the collected X-ray data were relatively high we could neither confirm the presence of a cyclotron line in the broad-band spectrum of the source (0.5-40 keV), nor detect any of the previously reported tentative detection of the source spin period. The monitoring carried out with Swift/XRT during the same orbit of the system observed by XMM-Newton and NuSTAR revealed that the source remained in a low emission state for most of the time, in agreement with the known property of all supergiant fast X-ray transients being significantly sub-luminous compared to other supergiant X-ray binaries. Optical and infrared observations were carried out for a total of a few thousands of seconds during the quiescence state of the source detected by XMM-Newton and NuSTAR. The measured optical and infrared magnitudes were slightly lower than previous values reported in the literature, but compatible with the known micro-variability of supergiant stars. UV observations obtained with the UVOT telescope on-board Swift did not reveal significant changes in the magnitude of the source in this energy domain compared to previously reported values.

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E. Bozzo, V. Bhalerao, P. Pradhan, J. Tomsick, P. Romano, C. Ferrigno, S. Chaty, L. Oskinova, A. Manousakis, R. Walter, M. Falanga, S. Campana, L. Stella, M. Ramolla, R. Chini. 2016-10-09. Multi-wavelength observations of IGR J17544-2619 from quiescence to outburst. https://doi.org/10.1051/0004-6361/201629311

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