EDP Sciences
Free access
Volume 405, Number 3, July III 2003
Page(s) 909 - 915
Section Galactic structure and dynamics
DOI http://dx.doi.org/10.1051/0004-6361:20030587

A&A 405, 909-915 (2003)
DOI: 10.1051/0004-6361:20030587

Spectral activity of the Seyfert galaxy Markarian 6 in 1970-1991

V. T. Doroshenko1 and S. G. Sergeev2

1  Crimean Laboratory of the Sternberg Astronomical Institute, University of Moscow, Russia; P/O Nauchny, 98409 Crimea, Ukraine Isaac Newton Institute of Chile, Crimean Branch
2  Crimean Astrophysical Observatory, P/O Nauchny, 98409 Crimea, Ukraine Isaac Newton Institute of Chile, Crimean Branch
    e-mail: sergeev@crao.crimea.ua

(Received 10 December 2002 / Accepted 21 March 2003)

We present results of the reduction of the archive spectra of the nucleus of Mrk 6 obtained in 1970-1991 using the image tube spectrograph at the 2.6-m Shajn telescope of the Crimean Astrophysical Observatory. We analyze 363 spectra for 181 dates obtained in the H $\beta$ spectral region. The spectra in the H $\alpha$ region (194 spectra for 179 dates) were used to get light curves. The light curves in the H $\beta$ and H $\alpha$ lines and also in the adjacent continuum show appreciable variability. Broad-line profile parameters (such as centroid, width, blue-to-red ratio of fluxes) seem to be independent of or dependent very weakly on the continuum flux. However, there is a tendency for the blue-to-red ratio of fluxes to increase with increasing continuum flux, and also a weak tendency for the profile width (profile dispersion) to decrease with increasing continuum flux. An anti-correlation between H $\beta$ shapes at the blue and red wings, positive correlation between blue shape and line/continuum flux, and anti-correlation between red shape and line/continuum flux show that the blue segments respond slightly better to the continuum changes than the red segment and total H $\beta$ line. We assume that the observed broad profile consists of at least two components with fixed profiles. We found that one of the components is nearly symmetric and has a single peak, while the other component has a blue bump and extended red wing. In terms of such a two-broad-components profile model, the evolution of the observed H $\beta$ profiles can be roughly reproduced by changes in the relative strength of the two variable components. However, the evolution of the broad H $\beta$ profile in Mrk 6 is complicated and not clear at all. The evolution is driven, most likely, by a set of various factor, including a multi-component BLR model with redistribution of ionizing radiation between different parts of the BLR, the matter redistribution, reverberation effects, and continuum-dependent changes.

Key words: galaxies: active -- galaxies: individual: Mrk 6 -- galaxies: nuclei -- galaxies: Seyfert

Offprint request: V. T. Doroshenko, doroshen@sai.crimea.ua

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