Publication Date:
2020-05-20
Description:
The dust reverberation mapping is one of powerful methods to investigate the structure of the dusty tori in active galactic nuclei (AGNs), and it has been performed on more than a hundred type 1 AGNs. However, no clear results have been reported on type 2 AGNs because their strong optical/UV extinction completely hides their accretion disc emission. Here, we focus on an X-ray-bright type 2 AGN, NGC 2110, and utilize 2–20 keV X-ray variation monitored by MAXI to trace disc emission, instead of optical/UV variation. Comparing it with light curves in the WISE infrared (IR) W1 band ($lambda =3.4~mu$m) and W2 band ($lambda =4.6~mu$m) with cross-correlation analyses, we found candidates of the dust reverberation time lag at ∼60, ∼130, and ∼1250 d between the X-ray flux variation and those of the IR bands. By examining the best-fitting X-ray and IR light curves with the derived time lags, we found that the time lag of ∼130 d is most favoured. With this time lag, the relation between the time lag and luminosity of NGC 2110 is consistent with those in type 1 AGNs, suggesting that the dust reverberation in NGC 2110 mainly originates in hot dust in the torus innermost region, the same as in type 1 AGNs. As demonstrated by the present study, X-ray and IR simultaneous monitoring can be a promising tool to perform the dust reverberation mapping on type 2 AGNs.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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