TY  - JOUR
A1  - Ignace, Richard
A1  - Oskinova, Lida
A1  - Massa, D.
T1  - A report on the X-ray properties of the tau Sco-like stars
JF  - Monthly notices of the Royal Astronomical Society
N2  - An increasing number of OB stars have been shown to possess magnetic fields. Although the sample remains small, it is surprising that the magnetic and X-ray properties of these stars appear to be far less correlated than expected. This contradicts model predictions, which generally indicate that the X-rays from magnetic stars are harder and more luminous than their non-magnetic counterparts. Instead, the X-ray properties of magnetic OB stars are quite diverse.
 tau Sco is one example where the expectations are better met. This bright main-sequence, early B star has been studied extensively in a variety of wavebands. It has a surface magnetic field of around 500 G, and Zeeman Doppler tomography has revealed an unusual field configuration. Furthermore, tau Sco displays an unusually hard X-ray spectrum, much harder than similar, non-magnetic OB stars. In addition, the profiles of its UV P Cygni wind lines have long been known to possess a peculiar morphology.
 Recently, two stars, HD 66665 and HD 63425, whose spectral types and UV wind line profiles are similar to those of tau Sco, have also been determined to be magnetic. In the hope of establishing a magnetic field - X-ray connection for at least a subset of the magnetic stars, we obtained XMM-Newton European Photon Imaging Camera spectra of these two objects. Our results for HD 66665 are somewhat inconclusive. No especially strong hard component is detected; however, the number of source counts is insufficient to rule out hard emission. Longer exposure is needed to assess the nature of the X-rays from this star. On the other hand, we do find that HD 63425 has a substantial hard X-ray component, thereby bolstering its close similarity to tau Sco.
KW  - stars: early-type
KW  - stars: individual: HD 63425
KW  - stars: individual: HD 66665
KW  - stars: magnetic field
KW  - X-rays: stars
Y1  - 2013
U6  - https://doi.org/10.1093/mnras/sts358
SN  - 0035-8711
VL  - 429
IS  - 1
SP  - 516
EP  - 522
PB  - Oxford Univ. Press
CY  - Oxford
ER  -