The bright Seyfert 1 galaxy mcg shows large variability on a variety of time scales. We study the $aproxlt 3$ day time scale variability using a set of simultaneous archival observations that were obtained from rxte and the {it Advanced Satellite for Cosmology and Astrophysics} (asca). The rxte observations span nearly $10^6$ sec and indicate that the X-ray Fourier Power Spectral Density has an rms variability of 16%, is flat from approximately 10^{-6} - 10^{-5} Hz, and then steepens into a power law $propto f^{-alpha}$ with $alphaaproxgt 1$. A further steepening to $alpha approx 2$ occurs between 10^{-4}-10^{-3} Hz. The shape and rms amplitude are comparable to what has been observed in gc and cyg, albeit with break frequencies that differ by a factor of 10^{-2} and 10^{4}, respectively. If the break frequencies are indicative of the central black hole mass, then this mass may be as low as $10^6 {rm M}_odot$. An upper limit of $sim 2$ 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 gc and cyg, this limit is consistent with a relatively low central black hole mass.
تحميل البحث