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

Matsumoto C.$^1$, and Inoue H.$^1$

$^1$ISAS, Sagamihara, Kanagawa, Japan


One of the most remarkable discoveries of ASCA is a broad and skewed
feature around 5--7~keV in the spectrum of the Seyfert-1 galaxy
MCG$-$6-30-15.  This feature is well explained by considering that it
is fluorescent lines coming from the innermost region of an accretion
disk.  If this interpretation is correct, the study of this profile is
very important.  In order to confirm the validity and correctness of
the disk-line interpretation, we investigated the iron line properties
of MCG$-$6-30-15, by more systematic and more model-independent ways
than previously done, by using the ASCA data of the three long-term
observations.  We made spectral analysis on short and long time
scales.  The ``Red'' line flux does not follow the continuum flux
on a time scale of $2\times10^4$~s. An inverse correlation was found
between the equivalent width and the continuum flux on a time scale of
$2\times10^5$~s.  We also evaluated variability amplitude of the count
rate on various time scales for 15~energy bands. It was suggested that
a presence of time variation on a time scale longer than 10$^{5}$~s,
which appears only in the continuum bands other than the disk-line
band. We make discussions both on the disk-line model and on an
alternative model.