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  • The Curious Case of ASASSN-...
    Hinkle, Jason T.; Holoien, Thomas W.-S.; Shappee, Benjamin. J.; Neustadt, Jack M. M.; Auchettl, Katie; Vallely, Patrick J.; Shahbandeh, Melissa; Kluge, Matthias; Kochanek, Christopher S.; Stanek, K. Z.; Huber, Mark E.; Post, Richard S.; Bersier, David; Ashall, Christopher; Tucker, Michael A.; Williams, Jonathan P.; de Jaeger, Thomas; Do, Aaron; Fausnaugh, Michael; Gruen, Daniel; Hopp, Ulrich; Myles, Justin; Obermeier, Christian; Payne, Anna V.; Thompson, Todd A.

    Astrophysical journal/˜The œAstrophysical journal, 05/2022, Letnik: 930, Številka: 1
    Journal Article

    Abstract We present observations of ASASSN-20hx, a nearby ambiguous nuclear transient (ANT) discovered in NGC 6297 by the All-Sky Automated Survey for Supernovae (ASAS-SN). We observed ASASSN-20hx from −30 to 275 days relative to the peak UV/optical emission using high-cadence, multiwavelength spectroscopy and photometry. From Transiting Exoplanet Survey Satellite data, we determine that the ANT began to brighten on 2020 June 22.8 with a linear rise in flux for at least the first week. ASASSN-20hx peaked in the UV/optical 30 days later on 2020 July 22.8 (MJD = 59052.8) at a bolometric luminosity of L = (3.15 ± 0.04) × 10 43 erg s −1 . The subsequent decline is slower than any TDE observed to date and consistent with many other ANTs. Compared to an archival X-ray detection, the X-ray luminosity of ASASSN-20hx increased by an order of magnitude to L x ∼ 1.5 × 10 42 erg s −1 and then slowly declined over time. The X-ray emission is well fit by a power law with a photon index of Γ ∼ 2.3–2.6. Both the optical and near-infrared spectra of ASASSN-20hx lack emission lines, unusual for any known class of nuclear transient. While ASASSN-20hx has some characteristics seen in both tidal disruption events and active galactic nuclei, it cannot be definitively classified with current data.