Abstract
Here we present results of the long-term (1987-2010) optical spectral monitoring of the broad line radio galaxy Arp 102B, a prototype of active galactic nuclei with the double-peaked broad emission lines, usually assumed to be emitted from an accretion disk. To explore the structure of the broad line region (BLR), we analyze the light curves of the broad H\alpha and H\beta lines and the continuum flux. We aim to estimate the dimensions of the broad-line emitting regions and the mass of the central black hole. We use the CCF to find lags between the lines and continuum variations. We investigate in more details the correlation between line and continuum fluxes, moreover we explore periodical variations of the red-to-blue line flux ratio using Lomb-Scargle periodograms. The line and continuum light curves show several flare-like events. The fluxes in lines and in the continuum are not showing a big change (around 20%) during the monitoring period. We found a small correlation between the line and continuum flux variation, that may indicate that variation in lines has weak connection with the variation of the central photoionization source. In spite of a low line-continuum correlation, using several methods, we estimated a time lag for H\beta around 20 days. The correlation between the H\beta and H\alpha flux variation is significantly higher than between lines and continuum. During the monitoring period, the H\beta and H\alpha lines show double-peaked profiles and we found an indication for a periodical oscillation in the red-to-blue flux ratio of the H\alpha line. The estimated mass of the central black hole is \sim 1.1 \times 10^8 M\odot that is in an agreement with the mass estimated from the M-\sigma* relation.
Highlights
The broad-line emission of active galactic nuclei (AGNs) that show two peaks in the broad-line component is assumed to originate in an accretion disk (Eracleous & Halpern 1994; Eracleous et al 1997, 2009)
We present results of long-term (1987–2010) optical spectral monitoring of the broad-line radio galaxy Arp 102B, a prototype of an active galactic nucleus with double-peaked broad emission lines that are commonly assumed to be emitted from an accretion disk
We investigated be caused by a central component in the broad-line region (BLR)
Summary
The broad-line emission of active galactic nuclei (AGNs) that show two peaks in the broad-line component is assumed to originate in an accretion disk (Eracleous & Halpern 1994; Eracleous et al 1997, 2009). These AGNs often show a variability in the broad emission lines and continuum 2011; Dietrich et al 2012). The broad-line region (BLR) is close to the central supermassive black hole and may hold fundamental information about the formation and fueling of AGNs
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