Article

Ultraviolet Spectral Evidence for Ansky as a Slowly Evolving Featureless Tidal Disruption Event with Quasiperiodic Eruptions

Jiazheng ZhuSchool of Astronomy and Space Sciences, University of Science and Technology of China, Hefei 230026, People's Republic of ChinaN. JiangSchool of Astronomy and Space Sciences, University of Science and Technology of China, Hefei 230026, People's Republic of ChinaYibo WangSchool of Astronomy and Space Sciences, University of Science and Technology of China, Hefei 230026, People's Republic of ChinaT. G. WangDepartment of Astronomy, University of Science and Technology of China, Hefei 230026, People's Republic of ChinaLuming SunDepartment of Physics, Anhui Normal University, Wuhu, Anhui 241002, People's Republic of ChinaShiyan ZhongSouth-Western Institute for Astronomy Research, Yunnan University, Kunming 650500 Yunnan, People's Republic of ChinaYuhan YaoMiller Institute for Basic Research in Science, 206B Stanley Hall, Berkeley, CA 94720, USAR. ChornockDepartment of Astronomy, University of California, Berkeley, CA 94720-3411, USALixin DaiDepartment of Physics, University of Hong Kong, Pokfulam Road, Hong Kong, People's Republic of ChinaJianwei LyuSteward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USAXinwen ShuDepartment of Physics, Anhui Normal University, Wuhu, Anhui 241002, People's Republic of ChinaC. FremlingCaltech Optical Observatories, California Institute of Technology, Pasadena, CA 91125, USAErica HammersteinDepartment of Astronomy, University of California, Berkeley, CA 94720-3411, USAShifeng HuangSchool of Astronomy and Space Sciences, University of Science and Technology of China, Hefei 230026, People's Republic of ChinaWenkai LiSchool of Astronomy and Space Sciences, University of Science and Technology of China, Hefei 230026, People's Republic of ChinaBei YouDepartment of Astronomy, School of Physics and Technology, Wuhan University, Wuhan 430072, People's Republic of China

2025en

ABI

Abstract

Abstract X-ray quasiperiodic eruptions (QPEs) are rare and enigmatic phenomena that increasingly show a connection to tidal disruption events (TDEs). However, the recently discovered QPEs in ZTF19acnskyy (“Ansky”) appear to be linked to an active galactic nucleus (AGN) rather than a TDE, as their slow decay and AGN-like variability differ markedly from that of typical TDEs. This finding may imply broader formation channels for QPEs. To further investigate Ansky’s nature, we obtained a timely ultraviolet (UV) spectrum, which reveals a featureless, TDE-like spectrum devoid of broad optical or UV emission lines. Additionally, the steep UV continuum, fitted by a power law with an index of −2.6, aligns more closely with TDEs than with AGNs. Compared to other featureless TDEs, Ansky exhibits a significantly lower blackbody luminosity (∼10 43 erg s −1 ) and much longer rise/decay timescales, suggesting a distinct TDE subclass. An offset TDE involving an intermediate-mass black hole is unlikely, given its position consistent with the galactic center, with a 3 σ upper limit of 54 pc. Instead, we propose that Ansky may result from the tidal disruption of a post-main-sequence star by a typical supermassive black hole. Our findings strengthen the growing evidence for TDE–QPE associations, although other formation channels for QPEs remain plausible and await future observational efforts.

Identifiers

DOI: 10.3847/2041-8213/ae19ea

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