Volume 476, Number 1, December II 2007
|Page(s)||317 - 320|
|Section||Stellar structure and evolution|
|Published online||02 October 2007|
XMM-Newton observations of the Small Magellanic Cloud: the 280 s Be/X-ray binary pulsar AX J0058-7203 in outburst*
Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, 85748 Garching, Germany e-mail: fwh;@mpe.mpg.de
Accepted: 27 September 2007
Context.The Be/X-ray binary pulsar AX J0058-720, discovered by ASCA, was in the field of view of the EPIC instruments during five XMM-Newton observations in the direction of the Small Magellanic Cloud (SMC).
Aims.We used the EPIC data of the X-ray pulsar in order to investigate its long-term temporal and spectral behaviour between 2000 and 2005.
Methods.X-ray spectra covering 0.3-10 keV and light curves in different energy bands were extracted from the EPIC PN and MOS data.
Results.The X-ray spectra are well modelled by a simple absorbed power-law without significant contribution from a soft component. The photon index of 0.7 indicates a relatively hard spectrum. During two observations in November 2005, separated by two days, the 0.2-10 keV luminosity reached a maximum of 2.6 1036 erg s-1 indicating an X-ray outburst. Twelve days later the source intensity had decreased by more than a factor of two. During an observation in November 2001 the source was not detected with a upper limit of 2.8 1033 erg s-1. Timing analysis of the observations of AX J0058-720 in 2005 reveals a pulse period of 286.3388±0.0012 s (or 286.8029±0.0012 s due to cycle count ambiguity). The average spin-down of ~0.75 s per year between 1997 and 2005 suggests a moderate activity episode with low average accretion rate, insufficient to spin-up the neutron star.
Conclusions.The X-ray properties of AX J0058-720 are typical for a Be/X-ray binary in the SMC. The source shows transient behaviour with more than a factor 900 intensity increases during outburst.
Key words: galaxies: individual: small Magellanic Cloud / galaxies: stellar content / stars: emission-line, Be / stars: neutron / X-rays: binaries
© 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.