Astronomy and Astrophysics – Astronomy
Scientific paper
Jun 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008arep...52..442d&link_type=abstract
Astronomy Reports, Volume 52, Issue 6, pp.442-462
Astronomy and Astrophysics
Astronomy
7
98.54.Cm, 95.85.Kr
Scientific paper
We have studied the variability of the H β line and the adjacent continuum in the spectrum of the Seyfert galaxy Ark 120, based on spectral observations of the galaxy’s nucleus obtained in the Crimea in 1992 2005, supplemented by published data for 1988 1996. Irregular variability on various timescales (years to days) can be accompanied by periodic brightness variations in both the continuum and the H β line, with a period of P ˜ 430 days and an amplitude of Δ m ˜ 0.2 m in the continuum, which were traced for more than 13 cycles. In total, in 1988 2005, the flux variations in the line lag those in the continuum by 55 ± 9 days if calculated from the peak of the cross correlation function, or by 72 ± 7 days, if calculated from the centroid of the CCF. The delay is correlated with the continuum brightness, increasing when the continuum flux increases. The H β line profiles indicate both a high degree of diversity and the presence of features that recur after various extended time intervals. Analysis of the evolution of the differences between each individual normalized line profile and the mean normalized profile indicates systematic motion of excesses relative to the average profile from negative to positive radial velocities. In contrast, parts of the H β line with low radiation relative to the mean normalized profile evolve in the opposite direction (from the red to the blue H β wing). This pattern is also typical for the rotating broad-line region, if this region has the form of a disk. The rotation period exceeds 9000 10000 days, or 25 27 years. The size of the broad-line region calculated form this period corresponds to a reverberation time of no fewer than 30 days, consistent with the results of cross-correlation analysis.
Doroshenko V. T.
Pronik Vladimir I.
Sergeev Sergey G.
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