The accretion environment in Vela X-1 during a flaring period using XMM-Newton

¹ Instituto Universitario de Física Aplicada a las Ciencias y las Tecnologías, University of Alicante, PO Box 99, 03080 Alicante, Spain
e-mail: silvia.martinez@ua.es
² Departamento de Física, Ingenería de Sistemas y Teoría de la Señal, University of Alicante, PO Box 99, 03080 Alicante, Spain
³ Dr. Karl Remeis-Observatory & ECAP, Universitat Erlangen-Nürnberg, Sternwartstr. 7, 96049 Bamberg, Germany
⁴ European Space Astronomy Centre (ESA/ESAC), Science Operations Department, Villanueva de la Cañada (Madrid), Spain
⁵ Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena CA 91125, USA
⁶ University College Dublin, Belfield, Dublin 4, Ireland

Received: 30 July 2013
Accepted: 26 December 2013

Abstract

We present analysis of 100 ks contiguous XMM-Newton data of the prototypical wind accretor Vela X-1. The observation covered eclipse egress between orbital phases 0.134 and 0.265, during which a giant flare took place, enabling us to study the spectral properties both outside and during the flare. This giant flare with a peak luminosity of 3.92^+0.42_-0.09 × 10³⁷ erg s^-1 allows estimates of the physical parameters of the accreted structure with a mass of ~10²¹ g. We have been able to model several contributions to the observed spectrum with a phenomenological model formed by three absorbed power laws plus three emission lines. After analysing the variations with orbital phase of the column density of each component, as well as those in the Fe and Ni fluorescence lines, we provide a physical interpretation for each spectral component. Meanwhile, the first two components are two aspects of the principal accretion component from the surface of the neutron star, the third component seems to be the X-ray light echo formed in the stellar wind of the companion.