Optical Continuum Reverberation in the Dwarf Seyfert Nucleus of NGC 4395

• Published in: Astrophysical journal. Letters 2022-08, Vol.934 (2), p.L37
• Main Authors: Montano, John W., Guo, Hengxiao, Barth, Aaron J., U, Vivian, Remigio, Raymond, González-Buitrago, Diego H., Hernández Santisteban, Juan V.
• Format: Article
• Language: English
• Subjects: Active galactic nuclei; Continuum radiation; Cross correlation; Dwarf galaxies; Emissions; Galaxies; Light curve; Luminosity; Night; Reverberation; Reverberation mapping; Seyfert galaxies
• ISSN: 2041-8205; 2041-8213
• DOI: 10.3847/2041-8213/ac7e54

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 − 1.09 + 1.01 , 14.16 − 1.25 + 1.22 , and 20.78 − 2.09 + 1.99 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 ∝ λ 4/3 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 τ gz ∝ L 0.56±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.