Letter to the Editor

RXTE confirmation of the intermediate polar status of Swift J0732.5–1331

¹ Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK e-mail: o.w.butters@open.ac.uk
² CRESST and X-ray Astrophysics Laboratory NASA/GSFC, Greenbelt, MD 20771, USA; Department of Physics, University of Maryland, Baltimore county, 1000 Hilltop Circle, Baltimore, MD 21250, USA

Received: 11 October 2007
Accepted: 18 September 2007

Abstract

Aims.We intend to establish the X-ray properties of Swift J0732.5–1331 and therefore confirm its status as an intermediate polar.

Methods.We analysed 36 240 s of X-ray data from RXTE. Frequency analysis was used to constrain temporal variations and spectral analysis used to characterise the emission and absorption properties.

Results.The X-ray spin period is confirmed to be 512.4(3) s with a strong first harmonic. No modulation is detected at the candidate orbital period of 5.6 h, but a coherent modulation is present at the candidate 11.3 h period. The spectrum is consistent with a 37 keV bremsstrahlung continuum with an iron line at 6.4 keV absorbed by an equivalent hydrogen column density of around 10²² atoms cm^-2.

Conclusions.Swift J0732–1331 is confirmed to be an intermediate polar.