Discovery of Short-Timescale Variability of Seyfert 2 Galaxy NGC 6300 with XMM-Newton

We found short time variability (Δ t ∼ 1 ks) of NGC 6300 in the 2--10 keV band with XMM-Newton. Its normalized power spectral density can be expressed by a power-law function of frequency with a slope of ∼-1.7. These results are similar to those of Seyfert 1 galaxies. Using the relation between time variability and central black hole mass, we estimate the black hole mass of about 3 × 10⁵ M_⊙. The time variability analysis suggests that NGC 6300 actually has a Seyfert 1 nucleus obscured by a thick matter.