AT 2023clx: The Faintest and Closest Optical Tidal Disruption Event Discovered in Nearby Star-forming Galaxy NGC 3799

Abstract

We report the discovery of a faint optical tidal disruption event (TDE) in the nearby star-forming galaxy NGC 3799. Identification of the TDE is based on its position at the galaxy nucleus, a light curve declining as t −5/3, a blue continuum with an almost constant blackbody temperature of ∼12,000 K, broad (≈15,000 km s−1) Balmer lines, and characteristic He ii 4686 Å emission. The light curve of AT 2023clx peaked at an absolute magnitude of −17.16 mag in the g band and a maximum blackbody bolometric luminosity of 4.56 × 1042 erg s−1, making it the faintest TDE discovered to date. With a redshift of 0.01107 and a corresponding luminosity distance of 47.8 Mpc, it is also the closest optical TDE ever discovered to the best of our knowledge. Furthermore, our analysis of Swift/XRT observations of AT 2023clx yields a very tight 3σ upper limit of 9.53 × 1039 erg s−1 in the range 0.3–10 keV. AT 2023clx, together with very few other faint TDEs such as AT 2020wey, prove that there are probably a large number of faint TDEs yet to be discovered at higher redshifts, which is consistent with the prediction of luminosity functions (LFs). The upcoming deeper optical time-domain surveys, such as the Legacy Survey of Space and Time and the Wide Field Survey Telescope, will discover more TDEs at even lower luminosities, allowing for a more precise constraint of the low end of the LF.

Detectability of Strongly Gravitationally Lensed Tidal Disruption Events

“…First, the emission line spectra in the UV/optical band are detectable. For example, the Balmer and/or Bowen lines facilitate the immediate classification of TDEs based on their spectral line characteristics (e.g., Gezari et al 2012;van Velzen et al 2021;Zhu et al 2023). Second, if the pre-peak evolution of emission lines is observable, it becomes feasible to determine the changes in velocity and opacity of the super-Eddington outflow by examining line width and intensity, respectively.…”

Astronomical or political: Interpretation of comets in times of crisis in Qing China

“…These additional information may be useful in several aspects. First, the emission line spectra in the UV/optical band are detectable, for example, the Balmer and/or Bowen lines, facilitates the immediate classification of TDEs based on their spectral line characteristics (e.g., Gezari et al 2012;van Velzen et al 2021;Zhu et al 2023). Secondly, if the pre-peak evolution of emission lines are observable, it becomes feasible to determine the changes in velocity and opacity of the super-Eddington outflow by examining linewidth and intensity, respectively.…”

The Unluckiest Star: A Spectroscopically Confirmed Repeated Partial Tidal Disruption Event AT 2022dbl

“…From 2024 January 22 to 2024 January 31, we conducted optical monitoring using the LCO Global Telescope network (Brown et al 2013) in the u, g, r, and i bands with daily cadence. With the same method as Zhu et al (2023), we use PanSTARRS (Flewelling et al 2020) gri-band stack images as reference images and employ HOTPANTS (Becker 2015) for image subtraction. After image subtraction, we perform PSF photometry on the difference image, and the photometric results are calibrated using PS1 standards in the field of view.…”