Issue |
A&A
Volume 697, May 2025
|
|
---|---|---|
Article Number | A159 | |
Number of page(s) | 23 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/202553669 | |
Published online | 16 May 2025 |
The population of tidal disruption events discovered with eROSITA
1
Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, 85748 Garching, Germany
2
Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
3
International Center for Radio Astronomy Research, Curtin University, GPO Box U1987, Perth, WA 6845, Australia
4
MIT Kavli Institute for Astrophysics and Space Research, 70 Vassar Street, Cambridge, MA 02139, USA
⋆ Corresponding author: grotova@mpe.mpg.de
Received:
3
January
2025
Accepted:
13
March
2025
Aims. The Spectrum Roentgen Gamma (SRG) eROSITA all-sky survey marks the beginning of the data-rich era by conducting population studies of tidal disruption events (TDEs) and other rare X-ray transients. This paper presents a systematic study of X-ray-selected canonical TDEs discovered in the western Galactic hemisphere of the first two eROSITA all-sky surveys (eRASS1 and eRASS2) performed between Dec 2019 and Dec 2020.
Methods. We compiled a TDE sample from the catalog of eROSITA's extragalactic transients and variables eRO-ExTra, which includes X-ray sources with a variability significance and fractional amplitude over four between eRASS1 and eRASS2, not associated with known active galactic nuclei (AGNs). Each X-ray source is associated with an optical counterpart from the Legacy Survey DR10 (LS10). Canonical TDEs were selected based on their X-ray light-curve properties (single flare or decline), soft X-ray spectra (Γ>3), and the absence of archival X-ray variability and AGN signatures in their host photometry and spectroscopy.
Results. We present 31 X-ray-selected TDE candidates associated with optical counterparts with redshifts of 0.02<z<0.34 and luminosities of 5.7×1041<LX<5.3×1044 ergs−1 in the 0.2−6.0 keV rest frame. The sample contains 30 canonical TDEs and one off-nuclear TDE candidate. The X-ray luminosity function derived from this sample is best fit by a double power law with a luminosity break at 1044 ergs−1, corresponding to the Eddington-limiting prediction. The result is in agreement with previous observational and theoretical estimates. This corresponds to a TDE volumetric rate of (2.3−0.9+1.2) × 10−7 Mpc−3 yr−1 (≈1.2×10−5 events per galaxy per year). The TDE host galaxies show a green-valley overdensity, as was previously found in X-ray and optical studies. In addition, 20%, 30%, and 15% of our X-ray-selected sample exhibit flares in the optical, mid-infrared (mid-IR), or radio bands, respectively. We discuss the differences between X-ray, optical, and mid-IR TDE populations and the origins of multiwavelength flares in the context of the obscuring envelope and stream-stream collision models. Finally, we highlight TDE subpopulations that are not included in the canonical sample and should be explored in the future.
Key words: accretion, accretion disks / black hole physics / galaxies: nuclei / X-rays: galaxies
© The Authors 2025
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This article is published in open access under the Subscribe to Open model.
Open Access funding provided by Max Planck Society.
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