| Type |
Journal Article |
| Names |
Asif ud-Doula, Stanley Owocki, Richard Townsend, Veronique Petit, David Cohen |
| Publication |
Monthly Notices of the Royal Astronomical Society |
| Volume |
441 |
| Issue |
4 |
| Pages |
3600-3614 |
| Journal Abbreviation |
Monthly Notices of the Royal Astronomical Society |
| Date |
July 1, 2014 |
| DOI |
10.1093/mnras/stu769 |
| ISSN |
0035-8711 |
| Short Title |
X-rays from magnetically confined wind shocks |
| URL |
http://adsabs.org/2014MNRAS.441.3600U |
| Library Catalog |
adslabs.org |
| Abstract |
We use 2D magnetohydrodynamic (MHD) simulations to examine the effects
of radiative cooling and inverse Compton (IC) cooling on X-ray emission
from magnetically confined wind shocks (MCWS) in magnetic massive stars
with radiatively driven stellar winds. For the standard dependence of
mass-loss rate on luminosity Ṁ˜ L1.7, the scaling
of IC cooling with L and radiative cooling with Ṁ means that IC
cooling become formally more important for lower luminosity stars.
However, because the sense of the trends is similar, we find the overall
effect of including IC cooling is quite modest. More significantly, for
stars with high enough mass-loss to keep the shocks radiative, the MHD
simulations indicate a linear scaling of X-ray luminosity with mass-loss
rate; but for lower luminosity stars with weak winds, X-ray emission is
reduced and softened by a shock retreat resulting from the larger
post-shock cooling length, which within the fixed length of a closed
magnetic loop forces the shock back to lower pre-shock wind speeds. A
semi-analytic scaling analysis that accounts both for the wind magnetic
confinement and this shock retreat yields X-ray luminosities that have a
similar scaling trend, but a factor few higher values, compared to
time-averages computed from the MHD simulations. The simulation and
scaling results here thus provide a good basis for interpreting
available X-ray observations from the growing list of massive stars with
confirmed large-scale magnetic fields. |
| Tags |
MHD, stars: early-type, stars: mass-loss |