High-resolution X-ray spectroscopy of the magnetic Of?p star HD148937
Y. Naze, S.A. Zhekov, N.R. Walborn
(ULg, U of Col. and Space and solar-terrestrial research inst., STScI)
High-resolution data of the peculiar magnetic massive star HD148937 were obtained with Chandra-HETGS, and are presented here in combination with a re-analysis of the older XMM-RGS data. The lines of the high-Z elements (Mg, Si, S) were found to be unshifted and relatively narrow (FWHM of about 800km/s), i.e. narrower than the O line recorded by RGS, which possibly indicates that the hot plasma is multi-thermal and has several origins. These data further indicate a main plasma temperature of about 0.6keV and a formation of the X-ray emission at about one stellar radius above the photosphere. From the spectral fits and the H-to-He line ratios, the presence of very hot plasma is however confirmed, though with a smaller relative strength than for the prototype magnetic oblique rotator $theta^1$,Ori,C. Both stars thus share many similarities, but HD148937 appears less extreme than $theta^1$,Ori,C despite having also a large magnetic confinement parameter.
Reference: accepted by ApJ
Status: Manuscript has been accepted