eROSITA-RU Tidal Disruption Events with Keck-I/LRIS: Sample Selection, Optical Properties, and Host Galaxy Demographics
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| Autores principales: | , , , , , , , , , , , , |
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| Formato: | Preprint |
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2025
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| author | Zhang, Zirui Yao, Yuhan Gilfanov, Marat Sazonov, Sergey Medvedev, Pavel Khorunzhev, Georgii Sunyaev, Rashid Ravi, Vikram Kulkarni, S. R. Somalwar, Jean Chornock, Ryan Bikmaev, Ilfan Gorbachev, Mark A. |
| author_facet | Zhang, Zirui Yao, Yuhan Gilfanov, Marat Sazonov, Sergey Medvedev, Pavel Khorunzhev, Georgii Sunyaev, Rashid Ravi, Vikram Kulkarni, S. R. Somalwar, Jean Chornock, Ryan Bikmaev, Ilfan Gorbachev, Mark A. |
| contents | We select seventy tidal disruption event (TDE) candidates among X-ray transients discovered during the eROSITA all-sky surveys in the Eastern Galactic hemisphere between December 2020 and February 2022 (eRASS1--5). We cross-match each X-ray source to a host galaxy in archival optical surveys using Bayesian likelihood-ratio techniques and obtain Keck/LRIS spectroscopy for all 70 host galaxies. Host properties are inferred through SED fitting with Prospector and emission line analysis with pPXF. We develop a robust classification scheme using X-ray and broad line luminosities, narrow-line ionization diagnostics, and optical variability to identify high-confidence TDEs, for which we analyze optical spectral features, light curve properties, and host galaxy demographics. Our final sample contains 52 TDEs with redshifts of $0.018 \leq z\leq0.714$, comprising 41 gold (high-confidence) and 11 silver (lower-confidence) events. The vast majority (93\%) of gold TDEs are intrinsically brighter in the X-ray band, with $L_{\rm X,peak} > L_{\rm opt,peak}$. Among 23 events with detected optical flares, delayed X-ray peak is commonly observed. We identify transient spectral features in eight events, including six with prominent broad \ion{He}{II} $λ$4686 and/or H$α$ emission and two coronal-line TDEs. Host galaxy demographics reveal modest over-representation in green valley ($\times1.8$) and quiescent Balmer-strong ($\times5.3$) galaxies, significantly weaker than previous TDE samples, demonstrating greater diversity in star formation histories than previously recognized. Most TDE hosts exhibit suppressed star formation relative to the main sequence, consistent with X-ray selection biases against dusty star-forming galaxies. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2512_12480 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | eROSITA-RU Tidal Disruption Events with Keck-I/LRIS: Sample Selection, Optical Properties, and Host Galaxy Demographics Zhang, Zirui Yao, Yuhan Gilfanov, Marat Sazonov, Sergey Medvedev, Pavel Khorunzhev, Georgii Sunyaev, Rashid Ravi, Vikram Kulkarni, S. R. Somalwar, Jean Chornock, Ryan Bikmaev, Ilfan Gorbachev, Mark A. High Energy Astrophysical Phenomena Astrophysics of Galaxies We select seventy tidal disruption event (TDE) candidates among X-ray transients discovered during the eROSITA all-sky surveys in the Eastern Galactic hemisphere between December 2020 and February 2022 (eRASS1--5). We cross-match each X-ray source to a host galaxy in archival optical surveys using Bayesian likelihood-ratio techniques and obtain Keck/LRIS spectroscopy for all 70 host galaxies. Host properties are inferred through SED fitting with Prospector and emission line analysis with pPXF. We develop a robust classification scheme using X-ray and broad line luminosities, narrow-line ionization diagnostics, and optical variability to identify high-confidence TDEs, for which we analyze optical spectral features, light curve properties, and host galaxy demographics. Our final sample contains 52 TDEs with redshifts of $0.018 \leq z\leq0.714$, comprising 41 gold (high-confidence) and 11 silver (lower-confidence) events. The vast majority (93\%) of gold TDEs are intrinsically brighter in the X-ray band, with $L_{\rm X,peak} > L_{\rm opt,peak}$. Among 23 events with detected optical flares, delayed X-ray peak is commonly observed. We identify transient spectral features in eight events, including six with prominent broad \ion{He}{II} $λ$4686 and/or H$α$ emission and two coronal-line TDEs. Host galaxy demographics reveal modest over-representation in green valley ($\times1.8$) and quiescent Balmer-strong ($\times5.3$) galaxies, significantly weaker than previous TDE samples, demonstrating greater diversity in star formation histories than previously recognized. Most TDE hosts exhibit suppressed star formation relative to the main sequence, consistent with X-ray selection biases against dusty star-forming galaxies. |
| title | eROSITA-RU Tidal Disruption Events with Keck-I/LRIS: Sample Selection, Optical Properties, and Host Galaxy Demographics |
| topic | High Energy Astrophysical Phenomena Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2512.12480 |