EDP Sciences
Free Access
Volume 436, Number 2, June III 2005
Page(s) 647 - 652
Section Stellar structure and evolution
DOI https://doi.org/10.1051/0004-6361:20042575
Published online 30 May 2005

A&A 436, 647-652 (2005)
DOI: 10.1051/0004-6361:20042575

INTEGRAL spectroscopy of the accreting millisecond pulsar XTE J1807-294 in outburst

M. Falanga1, J. M. Bonnet-Bidaud1, J. Poutanen2, R. Farinelli3, A. Martocchia4, P. Goldoni1, J. L. Qu5, L. Kuiper6 and A. Goldwurm1

1  CEA Saclay, DSM/DAPNIA/Service d'Astrophysique (CNRS FRE 2591), 91191 Gif-sur-Yvette, France
    e-mail: mfalanga@cea.fr
2  Astronomy Division, PO Box 3000, 90014 University of Oulu, Finland
3  Dipartimento di Fisica, Università di Ferrara, via Paradiso 12, 44100 Ferrara, Italy
4  Observatoire Astronomique, 11 rue de l'Université, 67000 Strasbourg, France
5  Laboratory for Particle Astrophysics, Institute of High Energy Physics, CAS, Beijing 100039, PR China
6  SRON National Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands

(Received 20 December 2004 / Accepted 7 March 2005 )

The transient X-ray accreting millisecond pulsar XTE J1807-294 was observed during its February/March 2003 outburst by INTEGRAL, partly simultaneously with the XMM-Newton and RXTE satellites. We present here the first study of the 0.5-200 keV broad-band spectra of the source. On February 28, the source spectrum was consistent with thermal Comptonization by electrons of temperature ~40 keV, considerably higher than the value (~10 keV) previously derived from the low energy XMM-Newton data alone. The source is detected by INTEGRAL up to 200 keV with a luminosity in the energy band (0.1-200) keV of $1.3 \times 10^{37}$ erg s-1 (assuming a distance of 8 kpc). 22 days later the luminosity dropped to $3.6 \times 10^{36}$ erg s-1. A re-analysis of XMM-Newton data yields the orbital Doppler variations of the pulse period and refines the previous ephemeris. For this source, with shortest orbital period of any known binary radio or X-ray millisecond pulsar, we constrain the companion mass $M_{\rm c} < 0.022~M_{\odot}$, assuming minimum mass transfer driven by gravitational radiation. Only evolved dwarfs with a C/O composition are consistent with the Roche lobe and gravitational radiation constraints, while He dwarfs require an unlikely low inclination.

Key words: accretion, accretion disks -- X-rays: binaries -- stars: individual: XTE J1807-294 -- stars: neutron

SIMBAD Objects

© ESO 2005

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.