Our goal is to understand the specificities of highly absorbed sgHMXB and in
particular of the companion stellar wind, thought to be responsible for the
strong absorption. We have monitored IGR J17252-3616, a highly absorbed system
featuring eclipses, with XMM-Newton to study the vari- ability of the column
density and of the Fe K{\alpha} emission line along the orbit and during the
eclipses. We also built a 3D model of the structure of the stellar wind to
reproduce the observed variability. We first derived a refined orbital solution
built from INTEGRAL, RXTE and XMM data. The XMM monitoring campaign revealed
significant variation of intrinsic absorbing column density along the orbit and
of the Fe K{\alpha} line equivalent width around the eclipses. The origin of
the soft X-ray absorption is modeled with an dense and extended hydrodynamical
tail, trailing the neutron star. This structure extends along most of the
orbit, indicating that the stellar wind is strongly disrupted by the neutron
star. The variability of the absorbing column density suggests that the
terminal velocity of the wind is smaller (~400 km/s) than observed in classical
systems. This can also explain the much stronger density perturbation inferred
from the observations. Most of the Fe K{\alpha} emission is generated in the
most inner region of the hydrodynamical tail. This region, that extends over a
few accretion radii, is ionized and does not contribute to the soft X-ray
absorption. We have built a qualitative model of the stellar wind of IGR
J17252-3616 that can represent the observations and suggest that highly
absorbed systems have a lower wind velocity than classical sgHMXB. This
proposal could be tested with de- tailed numerical simulations and
high-resolution infrared/optical observations. If confirmed, it may turn out
that half of the persistent sgHMXB have low stellar wind speeds.Comment: 9 pages, 8 figure
