Iron Line Properties of the Seyfert 1 Galaxy MCG $-$ 6-30-15 Observed with ASCA

Abstract

Abstract We analyzed the data sets of three long observations of the Seyfert 1 galaxy MCG$-$6-30-15 performed with ASCA. We firstly confirmed the common presence of a broad and skewed feature (the so-called disk-line) in the average spectra of the three observations (namely, on a time scale of several times $10^{5} \,\mathrm{s}$). We then investigated the variability of the line flux and the profile on a time scale of $2 \times 10^4 \,\mathrm{s}$, approximating the profile with a double-Gaussian model: a relatively broad line at 5.5 keV (Red line) and a relatively narrow line at 6.4 keV (Blue line). The variability of the Red line is rather larger than that of the continuum flux in some cases; on the other hand, the equivalent width of the Blue line is not rejected to be constant in some cases. No significant correlation between the Red line flux and the Blue line flux is observed. We also evaluated the RMS variability (the standard deviation normalized by the mean) in 15 energy bands on various time-bin-widths using the longest data in 1999. We found that the RMS variability is reduced in the 5.0–6.6 keV band, and that the degree of the depression is more significant on the longer time-bin-width.