Bibcode
Oknyansky, V. L.; Gaskell, C. M.; Huseynov, N. A.; Mikailov, Kh. M.; Lipunov, V. M.; Shatsky, N. I.; Tsygankov, S. S.; Gorbovskoy, E. S.; Tatarnikov, A. M.; Metlov, V. G.; Malanchev, K. L.; Brotherton, M. B.; Kasper, D.; Du, P.; Chen, X.; Burlak, M. A.; Buckley, D. A. H.; Rebolo, R.; Serra-Ricart, M.; Podesta, R.; Levato, H.
Referencia bibliográfica
Odessa Astronomical Publications, vol. 30, p. 117 (2017)
Fecha de publicación:
1
2017
Número de citas
6
Número de citas referidas
5
Descripción
Optical and near-infrared photometry, optical spectroscopy, and soft
X-ray and UV monitoring of the changing-look active galactic nucleus NGC
2617 show that it continues to have the appearance of a type-1 Seyfert
galaxy. An optical light curve for 2010-2017 indicates that the change
of type probably occurred between 2010 October and 2012 February and was
not related to the brightening in 2013. In 2016 and 2017 NGC 2617
brightened again to a level of activity close to that in 2013 April.
However, in 2017 from the end of the March to end of July 2017 it was in
very low level and starting to change
back to a Seyfert 1.8. We find variations in all passbands and in both
the intensities and profiles of the broad Balmer lines. A new displaced
emission peak has appeared in Hβ. X-ray variations are well
correlated with UV-optical variability and possibly lead by ˜2-3
d. The K band lags the J band by about 21.5 ± 2.5 d and lags the
combined B + J bands by ˜25 d. J lags B by about 3 d. This could
be because J-band variability arises predominantly
from the outer part of the accretion disc, while K-band variability is
dominated by thermal re-emission by dust. We propose that spectral-type
changes are a result of increasing central luminosity causing
sublimation of the
innermost dust in the hollow bi-conical outflow. We briefly discuss
various other possible reasons that
might explain the dramatic changes in NGC 2617.