Optical continuum reverberation in the dwarf Seyfert nucleus of NGC 4395
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In order to constrain the size of the optical continuum emission region in the dwarf Seyfert 1 galaxy NGC 4395 through reverberation mapping, we carried out high-cadence photometric monitoring in the griz filter bands on two consecutive nights in 2022 April using the four-channel MuSCAT3 camera on the Faulkes Telescope North at Haleakalā Observatory. Correlated variability across the griz bands is clearly detected, and the r-, i-, and z-band light curves show lags of - + 7.72 +1.01 -1.09, 14.16 +1.22-1.25, and 20.78 +1.99-2.09 minutes with respect to the g band when measured using the full-duration light curves. When lags are measured for each night separately, the Night 2 data exhibit lower cross-correlation amplitudes and shorter lags than the Night 1 light curves. Using the full-duration lags, we find that the lag–wavelength relationship is consistent with the τ ∝ λ4/3 dependence found for more luminous active galactic nuclei. Combining our results with continuum lags measured for other objects, the lag between g and z band scales with optical continuum luminosity as τgz ∝ L0.56±0.05, similar to the scaling of broad-line region size with luminosity, reinforcing recent evidence that diffuse continuum emission from the broad-line region may contribute substantially to optical continuum variability and reverberation lags.
Montano , J W , Guo , H , Barth , A J , U , V , Remigio , R , González-Buitrago , D H & Hernández Santisteban , J V 2022 , ' Optical continuum reverberation in the dwarf Seyfert nucleus of NGC 4395 ' , Astrophysical Journal Letters , vol. 934 , no. 2 , L37 . https://doi.org/10.3847/2041-8213/ac7e54
Astrophysical Journal Letters
Copyright © 2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
DescriptionFunding information: LCO telescope time was granted by NOIRLab through the Mid-Scale Innovations Program (MSIP). MSIP is funded by NSF. This Letter is based on observations made with the MuSCAT3 instrument, developed by the Astrobiology Center and under financial supports by JSPS KAKENHI (JP18H05439) and JST PRESTO (JPMJPR1775), at Faulkes Telescope North on Maui, HI, operated by the Las Cumbres Observatory. Research at UC Irvine was supported by NSF grant AST-1907290. D.H.G.-B. acknowledges CONACYT support #319800. J.V.H.S. acknowledges support from STFC grant ST/R000824/1.
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