Dust reverberation mapping of Z229-15
: Mandal Amit Kumar, Rakshit Suvendu, Stalin CS, Wylezalek Dominika, Patig Markus Kissler, Sagar Ram, Mathew Blesson, Muneer S, Pal Indrani
Publisher: OXFORD UNIV PRESS
: 2021
: Monthly Notices of the Royal Astronomical Society
: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
: MON NOT R ASTRON SOC
: 501
: 3
: 3905
: 3915
: 11
: 0035-8711
: 1365-2966
DOI: https://doi.org/10.1093/mnras/staa3828
: https://research.utu.fi/converis/portal/detail/Publication/53416104
We report results of the dust reverberation mapping (DRM) on the Seyfert 1 galaxy Z229-15 at z = 0.0273. Quasi-simultaneous photometric observations for a total of 48 epochs were acquired during the period 2017 July to 2018 December in B, V, J, H and K-s bands. The calculated spectral index (α) between B and V bands for each epoch was used to correct for the accretion disc (AD) component present in the infrared light curves. The observed α ranges between -0.99 and 1.03. Using cross-correlation function analysis we found significant time delays between the optical V and the AD corrected J, H and Ks light curves. The lags in the rest frame of the source are 12.52(-9.55)(+10.00) d (between V and J), 15.63-5.11+5.05 d (between V and H) and 20.36-5.68 +5.82 d (between V and Ks). Given the large error bars, these lags are consistent with each other. However, considering the lag between V and K-s bands to represent the inner edge of the dust torus, the torus in Z229-15 lies at a distance of 0.017 pc from the central ionizing continuum. This is smaller than that expected from the radius luminosity (R-L) relationship known from DRM. Using a constant α = 0.1 to account for the AD component, as is normally done in DRM, the deduced radius (0.025 pc) lies close to the expected R-L relation. However, usage of constant a in DRM is disfavoured as the alpha of the ionizing continuum changes with the flux of the source.
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