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  • A Bright Ultraviolet Excess...
    Burke, J.; Howell, D. A.; Sarbadhicary, S. K.; Sand, D. J.; Amaro, R. C.; Hiramatsu, D.; McCully, C.; Pellegrino, C.; Andrews, J. E.; Brown, P. J.; Itagaki, Koichi; Shahbandeh, M.; Bostroem, K. A.; Chomiuk, L.; Hsiao, E. Y.; Smith, Nathan; Valenti, S.

    The Astrophysical journal, 10/2021, Volume: 919, Issue: 2
    Journal Article

    Abstract We present photometric and spectroscopic observations of the nearby Type Ia SN 2019yvq, from its discovery ∼1 day after explosion to ∼100 days after its peak brightness. This SN exhibits several unusual features, most notably an extremely bright UV excess seen within ∼5 days of its explosion. As seen in Swift UV data, this early excess outshines its “peak” brightness, making this object more extreme than other supernovae (SNe) with early UV/blue excesses (e.g., iPTF14atg and SN 2017cbv). In addition, it was underluminous M B = −18.4, relatively quickly declining (Δ m 15 ( B ) = 1.37), and shows red colors past its early blue bump. Unusual (although not unprecedented) spectral features include extremely broad-lined and high-velocity Si absorption. Despite obvious differences in peak spectra, we classify SN 2019yvq as a transitional member of the 02es-like subclass due to its similarities in several respects (e.g., color, peak luminosity, peak Ti, and nebular Ca ii ). We model this data set with a variety of published models, including SN ejecta–companion shock interaction and sub-Chandrasekhar-mass white dwarf (WD) double-detonation models. Radio constraints from the VLA place an upper limit of (4.5–20) × 10 −8 M ⊙ yr −1 on the mass-loss rate from a symbiotic progenitor, which does not exclude a red giant or main-sequence companion. Ultimately, we find that no one model can accurately replicate all aspects of the data set, and further we find that the ubiquity of early excesses in 02es-like SNe Ia requires a progenitor system that is capable of producing isotropic UV flux, ruling out some models for this class of objects.