Astronomers from around the world have conducted extensive multiwavelength observations of AT 2023clx, identified as the closest tidal disruption event (TDE) to Earth. The findings, published on the pre-print server arXiv on Jan. 22, provide crucial information about the characteristics of this TDE. TDEs occur when a star comes too close to a supermassive black hole, leading to its fragmentation by tidal forces. The resulting disrupted stellar debris falls onto the black hole, emitting radiation from the innermost accreting debris region—a key indicator of a TDE.
Situated approximately 155.8 million light years away in the nucleus of the galaxy NGC 3799, AT 2023clx stands out as the nearest known optical TDE. First recognized as a transient in 2014 and subsequently classified as a TDE in July 2023, it holds the distinction of being one of the faintest tidal disruption events with a maximum blackbody luminosity of only 4.56 tredecillion erg/s.
As AT 2023clx is a recently discovered TDE, its properties were largely unknown, prompting a comprehensive study by a team of astronomers led by Panos Charalampopoulos from the University of Turku in Finland. Utilizing various space telescopes and ground-based observatories, including NASA’s Swift spacecraft and the Nordic Optical Telescope (NOT), the researchers conducted extensive observations in optical, near-infrared, and ultraviolet bands.
The study unveiled that AT 2023clx exhibited a peak absolute magnitude of −18.25 mag in the g-band and a maximum bolometric luminosity of 32.4 tredecillion erg/s, categorizing it as an intermediate luminosity TDE. The supermassive black hole’s estimated mass was around 1 million solar masses.
Notably, AT 2023clx reached its peak within an exceptionally swift 10.4 days, marking it as the fastest rising TDE documented to date. The researchers propose that this rapid rise resulted from the disruption of a very low-mass star (below 0.1 solar masses) with an impact parameter of approximately 0.8.
Spectroscopic analysis unveiled a blue continuum with slowly cooling features and broad Balmer and helium lines—a characteristic commonly observed in tidal disruption events. The lines exhibited a gradual narrowing over time as luminosity dropped, consistent with patterns seen in other TDEs.
A distinctive discovery from the observations of AT 2023clx was the identification of a sharp, narrow emission peak at a rest wavelength of about 6353 Å, situated atop the blue side of the broad hydrogen-alpha profile. This feature represents the first occurrence of such an observation in a TDE.
In summary, the researchers conclude that AT 2023clx resulted from the tidal disruption of a low-mass, small-radius star with low central concentration, approaching full disruption but remaining below the critical value. They suggest that such a disruption should exhibit a sharper rise and a shallower decline in light curves compared to other disruptions.