Optical Variability of the Dwarf AGN NGC 4395 from the Transiting Exoplanet Survey Satellite

Burke, Colin J.; Shen, Yue; Chen, Yu Ching; Scaringi, Simone; Faucher-Giguère, Claude André; Liu, Xin; Yang, Qian

doi:10.3847/1538-4357/aba3ce

“…The small physical size of the AGN in NGC 4395 results in much shorter timescales for variability and reverberation at ultraviolet (UV) and optical wavelengths than are typical of luminous AGN. By fitting the TESS light curve of NGC 4395 with a damped random walk (DRW) model, Burke et al (2020) found the DRW damping timescale to be t = -+ 2.3 DRW 0.7…”

Section: Introductionmentioning

confidence: 99%

Optical Continuum Reverberation in the Dwarf Seyfert Nucleus of NGC 4395

Montano¹,

Guo²,

Barth³

et al. 2022

ApJL

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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 − 1.09 + 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.

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“…The small physical size of the AGN in NGC 4395 results in much shorter timescales for variability and reverberation at ultraviolet (UV) and optical wavelengths than are typical of luminous AGN. By fitting the TESS light curve of NGC 4395 with a damped random walk (DRW) model, Burke et al (2020) found the DRW damping timescale to be τ DRW = 2.3 +1.8 −0.7 days, in contrast to luminous AGN having τ DRW in the range of hundreds to thousands of days. Its broad emission-line reverberation lags are just ∼1 hour, both for the C IV λ1549 line measured relative to the 1350 Å continuum (Peterson et al 2005) and for the Hα line measured relative to the V -band continuum (Woo et al 2019;Cho et al 2020).…”

Section: Introductionmentioning

confidence: 99%

Optical Continuum Reverberation in the Dwarf Seyfert Nucleus of NGC 4395

Montano,

Guo,

Barth

et al. 2022

Preprint

2

0

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The nearby dwarf spiral galaxy NGC 4395 contains a broad-lined active galactic nucleus (AGN) of exceptionally low luminosity powered by accretion onto a central black hole of very low mass (∼ 10 4 − 10 5 M ). In order to constrain the size of the optical continuum emission region through reverberation mapping, we carried out high-cadence photometric monitoring of NGC 4395 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 8.4 +1.0 −1.1 , 14.2 +1.2 −1.4 , and 20.4 +2.0 −2.1 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 lagwavelength relationship is consistent with the τ ∝ λ 4/3 dependence found for more luminous AGN. 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.

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“…den Brok et al (2015) obtained a black hole mass estimate of 4.0 +2.7 −1.0 × 10 5 M via gas dynamical modelling; Brum et al (2019) similarly obtained 2.5 +1.0 −0.8 × 10 5 M via gas kinematics. These direct measurements were preceded by informative RM black hole mass estimates of (3.6±1.1)× 10 5 M (Peterson et al, 2005) and (4.9 ± 2.6) × 10 4 M (Edri et al, 2012, see also Cho et al 2020 andBurke et al 2020). Likewise, NGC 3319* could greatly benefit from further study by RM campaigns, or at least single-epoch spectra mass estimates.…”

Section: Direct Measurements Of Ngc 3319*mentioning

confidence: 99%

Refining the mass estimate for the intermediate-mass black hole candidate in NGC 3319

Davis,

Graham

2021

Preprint

0

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Recent X-ray observations by Jiang et al. have identified an active galactic nucleus (AGN) in the bulgeless spiral galaxy NGC 3319, located just 14.3 ± 1.1 Mpc away, and suggest the presence of an intermediate-mass black hole (IMBH; 10 2 ≤ M•/M ≤ 10 5 ) if the Eddington ratios are as high as 3 to 3 × 10 −3 . In an effort to refine the black hole mass for this (currently) rare class of object, we have explored multiple black hole mass scaling relations, such as those involving the (not previously used) velocity dispersion, logarithmic spiral-arm pitch angle, total galaxy stellar mass, nuclear star cluster mass, rotational velocity, and colour of NGC 3319, to obtain ten mass estimates, of differing accuracy. We have calculated a mass of 3.14 +7.02 −2.20 × 10 4 M , with a confidence of 84% that it is ≤10 5 M , based on the combined probability density function from seven of these individual estimates. Our conservative approach excluded two black hole mass estimates (via the nuclear star cluster mass, and the fundamental plane of black hole activity -which only applies to black holes with low accretion rates) that were upper limits of ∼10 5 M , and it did not use the M•-L 2−10 keV relation's prediction of ∼10 5 M . This target provides an exceptional opportunity to study an IMBH in AGN mode and advance our demographic knowledge of black holes. Furthermore, we introduce our novel method of meta-analysis as a beneficial technique for identifying new IMBH candidates by quantifying the probability that a galaxy possesses an IMBH.

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Optical Variability of the Dwarf AGN NGC 4395 from the Transiting Exoplanet Survey Satellite

Cited by 27 publications

References 39 publications

Optical Continuum Reverberation in the Dwarf Seyfert Nucleus of NGC 4395

Optical Continuum Reverberation in the Dwarf Seyfert Nucleus of NGC 4395

Optical Continuum Reverberation in the Dwarf Seyfert Nucleus of NGC 4395

Refining the mass estimate for the intermediate-mass black hole candidate in NGC 3319

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