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

Abstract

We present optical light curves from the Transiting Exoplanet Survey Satellite (TESS) for the archetypical dwarf active galactic nucleus (AGN) in the nearby galaxy NGC 4395 hosting a $\sim 10^5{M}_{\odot }$ supermassive black hole (SMBH). Significant variability is detected on timescales from weeks to hours before reaching the background noise level. The $\sim$month-long, 30 minute-cadence, high-precision TESS light curve can be well fit by a simple damped random walk (DRW) model, with the damping timescale ${\tau }_{\mathrm{DRW}}$ constrained to be $2.3_{-0.7}^{+1.8}$~days ($1\sigma$). NGC 4395 lies almost exactly on the extrapolation of the ${\tau }_{\mathrm{DRW}}-M_{\mathrm{BH}}$ relation measured for AGNs with BH masses that are more than three orders of magnitude larger. The optical variability periodogram can be well fit by a broken power law with the high-frequency slope ($-1.88\pm 0.15$) and the characteristic timescale (${\tau }_{\mathrm{br}}\equiv 1/(2\pi f_{\mathrm{br}})=1.4_{-0.5}^{+1.9}$days) consistent with the DRW model within 1$\sigma$. This work demonstrates the power of TESS light curves in identifying low-mass accreting SMBHs with optical variability, and a potential global ${\tau }_{\mathrm{DRW}}-M_{\mathrm{BH}}$ relation that can be used to estimate SMBH masses with optical variability measurements.

12 pages, 5 figures, 1 table. Accepted for publication in ApJ

References in corpus (9)

• Some Aspects of Measurement Error in Linear Regression of Astronomical Data
• astroquery: An Astronomical Web-Querying Package in Python
• Modeling the Time Variability of SDSS Stripe 82 Quasars as a Damped Random Walk
• Are the Variability Properties of the Kepler AGN Light Curves Consistent with a Damped Random Walk?
• Optical variability of AGN in the PTF/iPTF survey
• Limitations on the recovery of the true AGN variability parameters using Damped Random Walk modeling
• A 10,000-solar-mass black hole in the nucleus of a bulgeless dwarf galaxy
• Introducing the Search for Intermediate-mass Black-hole In Nearby Galaxy (SIBLING) Survey
• A close look at the dwarf AGN of NGC 4395: optical and near-IR integral field spectroscopy

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