With 40 ks of Chandra ACIS-S3 exposure , new information on both the starburst and QSO components of the X-ray emission of Markarian 231 , an ultraluminous infrared galaxy and Broad Absorption Line QSO , has been obtained .
The bulk of the X-ray luminosity is emitted from an unresolved nuclear point source , and the spectrum is remarkably hard with the majority of the flux emitted above 2 keV .
Most notably , significant nuclear variability ( a decrease of \sim 45 \% in approximately 6 hours ) at energies above 2 keV indicates that Chandra has probed within light hours of the central black hole .
Though we concur with Maloney & Reynolds that the direct continuum is not observed , this variability coupled with the 188 eV upper limit on the equivalent width of the Fe K \alpha emission line argues against the reflection-dominated model put forth by these authors based on their ASCA data .
Instead , we favor a model in which a small , Compton-thick absorber blocks the direct X-rays , and only indirect , scattered X-rays from multiple lines of sight can reach the observer .
Extended soft , thermal emission encompasses the optical extent of the galaxy and exhibits resolved structure .
An off-nuclear X-ray source with a 0.35–8.0 keV luminosity of L _ { X } = 7 \times 10 ^ { 39 } erg s ^ { -1 } , consistent with the ultraluminous X-ray sources in other nearby starbursts , is detected .
We also present an unpublished FOS spectrum from the HST archive showing the broad C iv absorption .