EDP Sciences
Free access
Issue
A&A
Volume 439, Number 1, August III 2005
Page(s) 255 - 263
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20052937


A&A 439, 255-263 (2005)
DOI: 10.1051/0004-6361:20052937

The 1-50 keV spectral and timing analysis of IGR J18027-2016: an eclipsing, high mass X-ray binary

A. B. Hill1, R. Walter2, C. Knigge1, A. Bazzano3, G. Bélanger4, A. J. Bird1, A. J. Dean1, J. L. Galache1, A. Malizia5, M. Renaud4, J. Stephen5 and P. Ubertini3

1  School of Physics and Astronomy, University of Southampton, Highfield, SO17 1BJ, UK
    e-mail: abh@astro.soton.ac.uk
2  Geneva Observatory, INTEGRAL Science Data Centre, Chemin d'Ecogia 16, 1291 Versoix, Switzerland
3  IASF-Rm, INAF, via Fosso del Cavaliere 100, 00133 Rome, Italy
4  CEA-Saclay, DAPNIA/Service d'Astrophysique, 91191 Gif-sur-Yvette Cedex, France
5  IASF-Bo, INAF, via Gobetti 101, 40129 Bologna, Italy

(Received 25 February 2005 / Accepted 24 April 2005)

Abstract
We report the association of the INTEGRAL source IGR J18027-2016 with the BeppoSAX source SAX J1802.7-2017. IGR J18027-2016 is seen to be a weak, persistent source by the IBIS/ISGRI instrument on board INTEGRAL with an average source count rate of 0.58 counts s-1 (~6.4 mCrab) in the 20-40 keV band. Timing analysis performed on the ISGRI data identifies an orbital period of of $4.5696 \pm 0.0009$ days and gives an ephemeris of mid-eclipse as, $T_{\rm mid} = 52\,931.37 \pm 0.04$ MJD. Re-analysis of archival BeppoSAX data has provided a mass function for the donor star, $f(m) = 16 \pm 1~M_{\odot}$ and a projected semimajor axis of $a_{x}\sin{i} = 68 \pm 1$ lt-s. We conclude that the donor is an OB-supergiant with a mass of 18.8-29.3 $M_{\odot}$ and a radius of 15.0-23.4 $R_{\odot}$. Spectra obtained by XMM-Newton and ISGRI indicate a high hydrogen column density of $N_{\rm H} = 6.8 \times 10^{22}$ cm-2, which suggests intrinsic absorption. The source appears to be a high mass X-ray binary with the neutron star emitting X-rays through wind-fed accretion while in an eclipsing orbit around an OB-supergiant.


Key words: X-rays: individual: IGR J18027-2016 -- X-rays: individual: SAX J1802.7-2017 -- X-rays: binaries -- pulsars: general -- gamma-rays: observations

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