Hunting for the Variable Iron Line in NGC 4258
Abstract
Aside from our own Galaxy, NGC 4258 hosts the supermasive black hole with the most precisely known mass and distance. Furthermore, we are viewing a nearly perfectly Keplerian, thin, warped accretion disk nearly edge-on, with our nuclear line of sight passing through the disk. The measured column in this source may be directly probing thedisk's accretion rate. NGC 4258 is also important in that it is emitting at only a small fraction of the Eddington luminosity, lying in logarithmic steps half way between bright Seyferts and the extremely low luminosity of Sgr A*. The former exhibit well-formed disk spectra and relativistically broadened Fe lines. The latter, such as M81* (which lies at lower fractional Eddington luminosity than NCG 4258) shows line structure revealed by Chandra-HETG observations which may be indicative of an advective flow. Here we shall discussthe variable, narrow line Fe structure revealed by a series of observations with Chandra-HETGS, XMM, and Suzaku. We compare these results to previous studies of M81* and the recent Chandra-HETGS observations of Sgr A*.
- Publication:
-
AAS/High Energy Astrophysics Division #14
- Pub Date:
- August 2014
- Bibcode:
- 2014HEAD...1410002N