- Runco, Jordan N;
- Cosens, Maren;
- Bennert, Vardha N;
- Scott, Bryan;
- Komossa, S;
- Malkan, Matthew A;
- Lazarova, Mariana S;
- Auger, Matthew W;
- Treu, Tommaso;
- Park, Daeseong
A sample of 102 local (0.02 < z < 0.1) Seyfert galaxies with black hole
masses MBH > 10^7 M_sun was selected from the Sloan Digital Sky Survey (SDSS)
and observed using the Keck 10-m telescope to study the scaling relations
between MBH and host galaxy properties. We study profile changes of the broad
Hbeta emission line within the ~3-9 year time-frame between the two sets of
spectra. The variability of the broad Hbeta emission line is of particular
interest, not only since it is used to estimate MBH, but also since its
strength and width is used to classify Seyfert galaxies into different types.
At least some form of broad-line variability (in either width or flux) is
observed in the majority (~66%) of the objects, resulting in a Seyfert-type
change for ~38% of the objects, likely driven by variable accretion and/or
obscuration. The broad Hbeta line virtually disappears in 3/102 (~3%) extreme
cases. We discuss potential causes for these changing-look AGNs. While similar
dramatic transitions have previously been reported in the literature, either on
a case-by-case basis or in larger samples focusing on quasars at higher
redshifts, our study provides statistical information on the frequency of
H$\beta$ line variability in a sample of low-redshift Seyfert galaxies.