Swift/XRT orbital monitoring of the candidate supergiant fast X-ray transient IGR J17354–3255
1
Institut für Astronomie und Astrophysik, Eberhard Karls
Universität,
Sand 1,
72076
Tübingen,
Germany
e-mail:
ducci@astro.uni-tuebingen.de
2
INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica – Palermo,
via U. La Malfa 153, 90146
Palermo,
Italy
3
INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica – Milano,
via E. Bassini 15, 20133
Milano,
Italy
4
ISDC, Data Center for Astrophysics of the University of Geneva,
Chemin d’Ecogia,
16 1290
Versoix,
Switzerland
5
NASA/Goddard Space Flight Center, Greenbelt, MD
20771,
USA
6
Universities Space Research Association,
Columbia,
MD,
USA
7
Department of Astronomy and Astrophysics, Pennsylvania State
University, University
Park, PA
16802,
USA
Received:
3
April
2013
Accepted:
7
June
2013
We report on the Swift/X-ray Telescope (XRT) monitoring of the field of view around the candidate supergiant fast X-ray transient (SFXT) IGR J17354–3255, which is positionally associated with the AGILE/GRID gamma-ray transient AGL J1734–3310. Our observations, which cover 11 days for a total on-source exposure of ~24 ks, span 1.2 orbital periods (Porb = 8.4474 d) and are the first sensitive monitoring of this source in the soft X-rays. These new data allow us to exploit the timing variability properties of the sources in the field to unambiguously identify the soft X-ray counterpart of IGR J17354–3255. The soft X-ray light curve shows a moderate orbital modulation and a dip. We investigated the nature of the dip by comparing the X-ray light curve with the prediction of the Bondi-Hoyle-Lyttleton accretion theory, assuming both spherical and nonspherical symmetry of the outflow from the donor star. We found that the dip cannot be explained with the X-ray orbital modulation. We propose that an eclipse or the onset of a gated mechanism is the most likely explanation for the observed light curve.
Key words: X-rays: binaries / stars: individual: IGR J17354-3255
© ESO, 2013