The shortest detected intra-day variability of active galactic nuclei in TESS survey

Abstract

AGNs are known to be variable in almost all wavelengths and timescales. The shortest variability timescale of AGNs can be used to probe the smallest scale structures within AGNs. We aim to measure the shortest detected variability timescale, $t_{min,ul}$, of type 1 radio-quiet Seyfert galaxies and analyse their characteristics. We extracted TESS light curves of 47 Seyfert 1 galaxies. We measured the PSDs of the sample, modelled by a power law model plus a constant noise, and constrained the shortest detected AGN variability timescale as the power law component exceeds the constant noise and systematic uncertainties indicated by the upper limits of non-variable quiescent galaxies' PSDs. We measured the upper limits of the shortest variability timescale to be $\log (t_{min,ul}/hrs)=0.85\pm 0.55$. We compared these upper limits to a range of theoretical AGN variability timescales, and the natural interpretation of our measured $t_{min,ul}$ is the light crossing scale from a coherently varying region, where the measured $t_{min,ul}$ corresponds to the range from a few to thousands of gravitational radii. A significant fraction of these light crossing scales is smaller than the accretion disk emission sizes measured by quasar microlensing, reverberation mapping, or theoretical accretion disk models. Since we only measure the upper limits, the true physical shortest variability timescales are even shorter. We measure the power law index to be $2.0\pm 0.2$, and find weak anticorrelations with the black hole mass and luminosity. Our analysis suggests that the shortest optical variability is driven by a compact region smaller than the accretion disk size, potentially by X-ray reprocessing. Alternatively, this shortest timescale variability suggests that the accretion disk can be inhomogeneous potentially caused by turbulence from magnetorotational instability or magnetic reconnections. (abridged)

arXiv comment10 pages, 8 figures, accepted for publication in A&A

References in corpus (53)

• The Man Behind the Curtain: X-rays Drive the UV through NIR Variability in the 2013 AGN Outburst in NGC 2617
• The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0
• 2MASS Extended Source Catalog: Overview and Algorithms
• Are the Variations in Quasar Optical Flux Driven by Thermal Fluctuations?
• Modeling the Time Variability of SDSS Stripe 82 Quasars as a Damped Random Walk
• Measuring the broadband power spectra of active galactic nuclei with RXTE
• The Lick AGN Monitoring Project: Broad-Line Region Radii and Black Hole Masses from Reverberation Mapping of Hbeta
• Combined Long and Short Timescale X-ray Variability of NGC4051 with RXTE and XMM-Newton
• The Quasar Accretion Disk Size -- Black Hole Mass Relation
• The Quasar Accretion Disk Size - Black Hole Mass Relation
• The AGN Black Hole Mass Database
• An Alternative Approach To Measuring Reverberation Lags in Active Galactic Nuclei
• BAT AGN Spectroscopic Survey I: Spectral Measurements, Derived Quantities, and AGN Demographics
• Multiwavelength Monitoring of the Dwarf Seyfert 1 Galaxy NGC 4395. I. A Reverberation-Based Measurement of the Black Hole Mass
• Space Telescope and Optical Reverberation Mapping Project. II. Swift and HST Reverberation Mapping of the Accretion Disk of NGC 5548
• Swift BAT Survey of AGN
• X-ray Fluctuation Power Spectral Densities of Seyfert 1 Galaxies
• Magnetic Reconnection and Hot Spot Formation in Black Hole Accretion Disks
• Kepler Observations of Rapid Optical Variability in Active Galactic Nuclei
• The Sizes of the X-ray and Optical Emission Regions of RXJ1131-1231
• X-ray variability of 104 active galactic nuclei. XMM-Newton power-spectrum density profiles
• Optical Variability in Active Galactic Nuclei: Starbursts or Disk Instabilities?
• A Cutoff in the X-ray Fluctuation Power Density Spectrum of the Seyfert 1 Galaxy NGC 3516
• A characteristic optical variability timescale in astrophysical accretion disks
• The scaling of the X-ray variability with black hole mass in AGN
• Revisiting Stochastic Variability of AGNs with Structure Functions
• X-Ray and Optical Microlensing in the Lensed Quasar PG 1115+080
• Quasar Optical Variability in the Palomar-QUEST Survey
• The Kepler Light Curves of AGN: A Detailed Analysis
• On the origin of radio-loudness in AGNs and its relationship with the properties of the central supermassive black hole
• Calibrating the correlation between black hole mass and X-ray variability amplitude: X-ray only black hole mass estimates for active galactic nuclei and ultra-luminous X-ray sources
• The Unified Model of Active Galactic Nuclei: II. Evolutionary Connection
• Quasar Spectral Slope Variability in the Optical Band
• A local baseline of the black hole mass scaling relations for active galaxies. IV. Correlations between $M_{\mathrm{BH}}$ and host galaxy $\sigma$, stellar mass, and luminosity
• The relationship between the X-ray variability and the central black hole mass
• Accretion Disk Sizes from Continuum Reverberation Mapping of AGN Selected from the ZTF Survey
• The Properties of Reconnection Current Sheets in GRMHD Simulations of Radiatively Inefficient Accretion Flows
• A long term study of AGN X-ray variability. Structure function analysis on a ROSAT-XMM quasar sample
• Early Time Light Curves of Type Ia Supernovae Observed with TESS
• Intra-night optical variability of core dominated radio quasars: the role of optical polarization
• Improved characterisation of intra-night optical variability of prominent AGN classes
• High-Cadence, Early-Time Observations of Core-Collapse Supernovae From the TESS Prime Mission
• The broad-line region and dust torus size of the Seyfert 1 galaxy PGC50427
• Short time-scale optical variability properties of the largest AGN sample observed with Kepler/K2
• Inhomogeneous accretion discs and the soft states of black hole X-ray binaries
• Optical Variability of the Dwarf AGN NGC 4395 from the Transiting Exoplanet Survey Satellite
• The K-band properties of Seyfert 2 galaxies
• Intra-Night Optical monitoring of three γ-ray detected Narrow-line Seyfert 1 galaxies
• Intranight Optical Variability of Radio-Quiet Weak Emission Line Quasars-III
• Update on the X-ray variability plane for active galactic nuclei: The role of the obscuration
• X-ray monitoring of gravitationally lensed radio-loud quasars with Chandra
• The Variability of the Narrow-line Seyfert 1 Galaxies from the PanSTARRS's View
• High frequency breaks in optical active galactic nuclei power spectral density