Line profile and continuum variability in the very broad-line Seyfert galaxy Mrk 926

Abstract

We present results of an intensive spectroscopic variability campaign of the very broad-line Seyfert 1 galaxy Mrk 926. Our aim is to investigate the broad-line region (BLR) by studying the intensity and line profile variations of this galaxy on short timescales. High signal-to-noise ratio(S/N) spectra were taken with the 9.2m Hobby-Eberly Telescope (HET) in identical conditions during two observing campaigns in 2004 and 2005. After the spectral reduction and internal calibration we achieved a relative flux accuracy of better than 1%. The rms profiles of the very broad Balmer lines have shapes that differ from their mean line profiles, consisting of two inner (v $\lesssim \pm$ 6000 km s${}^{-1}$) and two outer (v $\gtrsim \pm$ 6000 km s${}^{-1}$) line components in addition to a central component (v $\lesssim \pm$ 600 km s${}^{-1}$). These outer and inner line segments varied with different amplitudes during our campaign. The radius of the BLR is very small with an upper limit of 2 light-days for the H$\beta$ BLR size. We derived an upper limit to the central black hole mass of $M=11.2\times 10^7{M}_{\odot }$. The 2-D cross-correlation functions CCF($\tau$,$v$) of H$\beta$ and H$\alpha$ are flat within the error limits. The response of the Balmer line segments with respect to continuum variations is different in the outer and inner wings of H$\alpha$ and H$\beta$. This double structure in the response curves - of two separate inner and outer components - has also been seen in the rms line profiles. We conclude that the outer and inner line segments originate in different regions and/or under different physical conditions.

13 pages, 18 figures, to be published in A&A

References in corpus (3)

• Long-Term Profile Variability of Double Peaked Emission Lines in Active Galactic Nuclei
• First Results from the Lick AGN Monitoring Project: The Mass of the Black Hole in Arp 151
• On the size of the Fe II emitting region in the AGN Akn 120

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