Astronomy and Astrophysics – Astrophysics – High Energy Astrophysical Phenomena
Scientific paper
2009-05-22
Astrophys.J.700:977-988,2009
Astronomy and Astrophysics
Astrophysics
High Energy Astrophysical Phenomena
29 pages, 8figures. accepted by ApJ
Scientific paper
10.1088/0004-637X/700/2/977
We present an analysis of several high-resolution Chandra grating observations of the X-ray binary pulsar Her X-1. With a total exposure of 170 ks, the observations are separated by years and cover three combinations of orbital and super-orbital phases. Our goal is to determine distinct properties of the photoionized emission and its dependence on phase-dependent variations of the continuum. We find that the continua can be described by a partial covering model which above 2 keV is consistent with recent results from \rxte studies and at low energies is consistent with recent \xmm and \sax studies. Besides a powerlaw with fixed index, an additional thermal blackbody of 114 eV is required to fit wavelengths above 12 \AA ($\sim$ 1 keV). We find that likely all the variability is caused by highly variable absorption columns in the range (1 -- 3)$\times 10^{23}$ cm$^{-2}$. Strong Fe K line fluorescence in almost all observations reveals that dense, cool material is present not only in the outer regions of the disk but interspersed throughout the disk. Most spectra show strong line emission stemming from a photoionized accretion disk corona. We model the line emission with generic thermal plasma models as well as with the photoionization code XSTAR and investigate changes of the ionization balance with orbital and superorbital phases. Most accretion disk coronal properties such as disk radii, temperatures, and plasma densities are consistent with previous findings for the low state. We find that these properties change negligibly with respect to orbital and super-orbital phases. A couple of the higher energy lines exhibit emissivities that are significantly in excess of expectations from a static accretion disk corona.
Ji Liangliang
Kallman Tim
Marshall Herman L.
Nowak Michael
Schulz Norbert
No associations
LandOfFree
The Photoionized Accretion Disk in Her X-1 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The Photoionized Accretion Disk in Her X-1, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Photoionized Accretion Disk in Her X-1 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-498995