The X-ray Halo and Spectrum of the Unusual O Star HD148937

We propose to observe the O star HD148937 for 30 ksec to measure both the Xrayhalo formed by dust scattering, as well as the spectrum of the star itself. TheXray halo measures the size and composition of large dust grains, which havemost of the mass that is in dust, but are difficult to observe at other wavelengths. HD148937, unlike most halo sources, has emission lines, and we can usethese to image the halo in narrow energy bands. The spectrum of HD148937 will bemeasured by the XMM RGS with over 6000 counts, enough to detect absorption anddoppler shifts of strong lines. HD148937 is an unusual O star, 20 times brighterthan the average O star with a harder spectrum. This will test current models ofO star winds, which have difficulty creating even the average luminosity. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]