TY  - JOUR
A1  - Grinberg, Victoria
A1  - Hell, Natalie
A1  - El Mellah, Ileyk
A1  - Neilsen, Joseph
A1  - Sander, Andreas Alexander Christoph
A1  - Leutenegger, Maurice
A1  - Fürst, Felix
A1  - Huenemoerder, David P.
A1  - Kretschmar, Peter
A1  - Kuehnel, Matthias
A1  - Martinez-Nunez, Silvia
A1  - Niu, Shu
A1  - Pottschmidt, Katja
A1  - Schulz, Norbert S.
A1  - Wilms, Joern
A1  - Nowak, Michael A.
T1  - The clumpy absorber in the high-mass X-ray binary Vela X-1
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Bright and eclipsing, the high-mass X-ray binary Vela X-1 offers a unique opportunity to study accretion onto a neutron star from clumpy winds of O/B stars and to disentangle the complex accretion geometry of these systems. In Chandra-HETGS spectroscopy at orbital phase similar to 0.25, when our line of sight towards the source does not pass through the large-scale accretion structure such as the accretion wake, we observe changes in overall spectral shape on timescales of a few kiloseconds. This spectral variability is, at least in part, caused by changes in overall absorption and we show that such strongly variable absorption cannot be caused by unperturbed clumpy winds of O/B stars. We detect line features from high and low ionization species of silicon, magnesium, and neon whose strengths and presence depend on the overall level of absorption. These features imply a co-existence of cool and hot gas phases in the system, which we interpret as a highly variable, structured accretion flow close to the compact object such as has been recently seen in simulations of wind accretion in high-mass X-ray binaries.
KW  - X-rays: individuals: Vela X-1
KW  - X-rays: binaries
KW  - stars: winds, outflows
KW  - stars: massive
Y1  - 2017
U6  - https://doi.org/10.1051/0004-6361/201731843
SN  - 1432-0746
VL  - 608
PB  - EDP Sciences
CY  - Les Ulis
ER  -