The observations shed more light on the characteristics of the nearest tidal disturbance event

An international team of astronomers has conducted multi-wavelength observations of AT 2023clx, the closest relative of a terrestrial tidal disruption event (TDE). Results of the monitoring campaign, published January 22 on preprint server arXivproviding important insights into the properties of TDE.

TDEs are astronomical phenomena that occur when a star passes close enough to a supermassive black hole and is pulled apart by the black hole's tidal forces, causing a turbulence process. Such tidally disrupted stellar debris begins to rain down on the black hole, and radiation emerges from the inner region of the accreting debris, an indication of the presence of a TDE.

AT 2023clx is located about 155.8 million light-years away, in the nucleus of galaxy NGC 3799, and is the closest known optical TDE. It was initially identified as a transient in 2014 and was classified as a TDE in July 2023. With a maximum blackbody luminosity at just 4.56 trillion erg/s, AT 2023clx is one of the faintest tidal disturbance events known.

Because AT 2023clx is a recently discovered TDE, very little is known about its properties. For this reason, a group of astronomers, led by Panos Charalambopoulos of the University of Turku in Finland, conducted an extensive study of the TDE in the optical, near-infrared and ultraviolet bands. For this purpose, they used several space telescopes and ground-based observation facilities, including NASA's Swift spacecraft and the Northern Optical Telescope (NOT).

“In this paper, we present the follow-up and comprehensive photometric and spectroscopic analysis of AT 2023clx,” the researchers wrote.

Observations found that AT 2023clx has an absolute peak of −18.25 mag in the g band and a maximum bolimetric luminosity at 32.4 trillion erg/s. This makes it a medium gloss TDE. The mass of the supermassive black hole has been estimated at about one million solar masses.

According to the study, AT 2023clx rose to its peak in 10.4 days, making it the fastest rising TDE known to date. Astronomers assume that such a rapid rise was caused by the perturbation of a very low-mass star (less than 0.1 solar mass) with a forcing factor of about 0.8.

Spectroscopic analysis revealed a slowly cooling blue continuum and broad Balmer and helium lines, which are typically observed in tidal disturbance events. The lines slowly become narrower over time as their luminosity decreases, which is also commonly seen in known TDEs.

Observations of AT 2023clx also found a sharp, narrow emission peak at a rest wavelength of about 6353 Å, just above the blue side of the broad hydrogen-alpha profile. This is the first time such a feature has been found in TDE.

Summarizing the results, the researchers note that AT 2023clx is the result of tidal turbulence of a small, low-mass radius star, with a low central concentration, close to complete turbulence but below the critical value. They add that such a disturbance should show a sharper rise and a shallower dip in the light curves than other disturbances.