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-Giguere, Claude-Andre; Liu, Xin; Yang, Qian

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 ~105 M⊙ supermassive black hole (SMBH). Significant variability is detected on timescales from weeks to hours before reaching the background noise level. The ~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 τDRW constrained to be ${2.3}_{-0.7}^{+1.8}$ days (1σ). 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 ± 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 1σ. 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.

Citation

Burke, C. J., Shen, Y., Chen, Y.-C., Scaringi, S., Faucher-Giguere, C.-A., Liu, X., & Yang, Q. (2020). Optical Variability of the Dwarf AGN NGC 4395 from the Transiting Exoplanet Survey Satellite. Astrophysical Journal, 899(2), https://doi.org/10.3847/1538-4357/aba3ce

• Journal Article Type: Article
• Acceptance Date: Jul 4, 2020
• Online Publication Date: Aug 24, 2020
• Publication Date: 2020
• Deposit Date: Dec 31, 2020
• Publicly Available Date: Aug 24, 2021
• Journal: Astrophysical Journal
• Print ISSN: 0004-637X
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 899
• Issue: 2
• DOI: https://doi.org/10.3847/1538-4357/aba3ce
• Public URL: https://durham-repository.worktribe.com/output/1283138