Implications of the X-Ray Variability for the Mass of MCG -6-30-15
Abstract
The bright Seyfert 1 galaxy MCG -6-30-15 shows large variability on a variety of timescales. We study the <~3 day timescale variability using a set of simultaneous archival observations that were obtained from the Rossi X-Ray Timing Explorer (RXTE) and the Advanced Satellite for Cosmology and Astrophysics (ASCA). The RXTE observations span nearly 106 s and indicate that the X-ray Fourier power spectral density has an rms variability of 16%, is flat from approximately 10-6 to 10-5 Hz, and then steepens into a power law proportional to f-α with α>~1. A further steepening to α~2 occurs between 10-4 and 10-3 Hz. The shape and rms amplitude are comparable to what has been observed in NGC 5548 and Cyg X-1, albeit with break frequencies that differ by a factor of 10-2 and 104, respectively. If the break frequencies are indicative of the central black hole mass, then this mass may be as low as 106 Msolar. An upper limit of ~2 ks for the relative lag between the 0.5-2 keV ASCA band compared to the 8-15 keV RXTE band was also found. Again by analogy with NGC 5548 and Cyg X-1, this limit is consistent with a relatively low central black hole mass.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 2000
- DOI:
- 10.1086/312508
- arXiv:
- arXiv:astro-ph/9906371
- Bibcode:
- 2000ApJ...531L..13N
- Keywords:
-
- GALAXIES: INDIVIDUAL: ALPHANUMERIC: MCG -6-30-15;
- GALAXIES: SEYFERT;
- X-RAYS: GALAXIES;
- Astrophysics
- E-Print:
- 5 pages, 3 figures, LaTeX, uses emulateapj.sty and apjfonts.sty, revised version, accepted for publication in ApJ Letters