CIR Modulation of the X-ray Flux from the O7.5 III(n)((f)) Star ξ Persei?
D. Massa, L. Oskinova, A.W. Fullerton, R.K. Prinja, D.A. Bohlender, N.D. Morrison, M. Blake and W. Pych
We analyze a 162 ks HETG Chandra observation of the O7.5 III(n)((f))
star ξ Per, together with contemporaneous Hα observations.
The X-ray spectrum of this star is similar to other single O stars, and
not pathological in any way. Its UV wind lines are known to display
cyclical time variability, with a period of 2.086 days, which is
thought to be associated with co-rotating interaction regions (CIRs).
We examine the Chandra and Hα data for variability on this time
scale. We find that the X-rays vary by 15% over the course of the
observations and that this variability is out of phase with variable
absorption on the blue wing of the Hα profiles (assumed to be a
surrogate for the UV absorption associated with CIRs). While not
conclusive, both sets of data are consistent with models where the CIRs
are either a source of X-rays or modulate them.