R. Sturm, F. Haberl, A. Rau, E. S. Bartlett, X. -L. Zhang, P. Schady, W. Pietsch, J. Greiner, M. J. Coe, A. Udalski
The number of known Be/X-ray binaries in the Large Magellanic Cloud is small
compared to the observed population of the Galaxy or the Small Magellanic
Cloud. The discovery of a system in outburst provides the rare opportunity to
measure its X-ray properties in detail. IGR J05414-6858 was serendipitously
found in outburst with the Swift satellite in August 2011. In order to
characterise the system, we analysed the data from a follow-up XMM-Newton
target of opportunity observation and investigate the stellar counterpart with
photometry and spectroscopy. We modelled the X-ray spectra from the EPIC
instruments on XMM-Newton and compared them with Swift archival data. In the
X-ray and optical light curves, we searched for periodicities and variability.
The optical counterpart was classified using spectroscopy obtained with ESO's
Faint Object Spectrograph at NTT. The X-ray spectra as seen in 2011 are
relatively hard with a photon index of ~0.3 - 0.4 and show only low absorption.
They deviate significantly from earlier spectra of a probable type II outburst
in 2010. The neutron star spin period of P_s = 4.4208 s was discovered with
EPIC-pn. The I-band light curve revealed a transition from a low to a high
state around MJD 54500. The optical counterpart is classified to B0-1IIIe and
shows Halpha emission and a variable NIR excess, vanishing during the 2010
outburst. In the optical high state, we found a periodicity at 19.9 days,
probably caused by binarity and indicating the orbital period.
View original:
http://arxiv.org/abs/1202.4967
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