General relativistic effects on the spectrum reflected by accretion disks around black holes

Making the usual assumption that the relatively cold matter within the cent ral engine of an active galactic nucleus (or galactic black hole candidate) is in the form of a relativistic accretion disk, we compute the composite spectrum of the original disk plus a primary X-ray power-law source illumin ating it from above, as well. as the reflected emission from the disk. All special and general relativistic effects on both infalling photons and outg oing photons are considered in a Schwarzschild geometry. The strength, shap e, and broadening of the reflected spectrum depend on the direction of the X-ray source relative to the disk and the observer's viewing angle. The re- flected photons extract energy and angular momentum from the relativistical ly rotating accretion disk and are beamed in the direction of the disk velo city. The reflection hump could essentially disappear if viewed far from th e symmetry axis because the X-ray photons are affected by gravity both appr oaching and leaving the disk. This may produce a difference between X-ray s pectra for Seyfert 1 and Seyfert 2 galaxies. For a given observation angle, the reflection hump is most sensitive to the inclination of the source rel ative to the accretion disk. Thus the spectral shape may also shed light on the location of the primary X-ray source, which is probably either in a je t or in a corona; however, additional computations involving distributed so urces will be necessary before detailed comparisons with observations are f easible.