Browsing by Author "Taggart, K."

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    Double “acct”: A Distinct Double-peaked Supernova Matching Pulsational Pair Instability Models
    (2024) Angus, C.R.; Woosley, S.E.; Foley, R.J.; Nicholl, M.; Villar, V.A.; Taggart, K.; Pursiainen, M.; Ramsden, P.; Srivastav, S.; Stevance, H.F.; Moore, T.; Auchettl, K.; Hoogendam, W.B.; Khetan, N.; Yadavalli, S.K.; Dimitriadis, G.; Gagliano, A.; Siebert, M.R.; Aamer, A.; Boer, T.D.; Chambers, K.C.; Clocchiatti García, Alejandro; Coulter, D.A.; Drout, M.R.; Farias, D.; Fulton, M.D.; Gall, C.; Gao, H.; Izzo, L.; Jones, D.O.; Lin, C.-C.; Magnier, E.A.; Narayan, G.; Ramirez-Ruiz, E.; Ransome, C.L.; Rest, A.; Smartt, S.J.; Smith, K.W.
    We present multiwavelength data of SN 2020acct, a double-peaked stripped-envelope supernova (SN) in NGC 2981 at ∼150 Mpc. The two peaks are temporally distinct, with maxima separated by 58 rest-frame days and a factor of 20 reduction in flux between. The first is luminous (Mr = −18.00 ± 0.02 mag) and blue (g − r = 0.27 ± 0.03 mag) and displays spectroscopic signatures of interaction with hydrogen-free circumstellar material. The second peak is fainter (Mr = −17.29 ± 0.03 mag) and has some spectroscopic similarities to an evolved stripped-envelope SN, with strong forbidden [Ca ii] and [O ii] features. No other known double-peaked SN exhibits a light curve similar to that of SN 2020acct. We find the likelihood of two individual SNe occurring in the same star-forming region within that time to be highly improbable, while an implausibly fine-tuned configuration would be required to produce two SNe from a single binary system. We find that the peculiar properties of SN 2020acct match models of pulsational pair instability (PPI), in which the initial peak is produced by collisions of shells of ejected material, shortly followed by core collapse. Pulsations from a star with a 72 M⊙ helium core provide an excellent match to the double-peaked light curve. The local galactic environment has a metallicity of 0.4 Z⊙, a level where massive single stars are not expected to retain enough mass to encounter the PPI. However, late binary mergers or a low-metallicity pocket may allow the required core mass. We measure the rate of SN 2020acct-like events to be <3.3 × 10−8 Mpc−3 yr−1 at z = 0.07, or <0.1% of the total core-collapse SN rate.
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    Final Moments. II. Observational Properties and Physical Modeling of Circumstellar-material-interacting Type II Supernovae
    (2024) Jacobson-Galan, W. V.; Dessart, L.; Davis, K. W.; Kilpatrick, C. D.; Margutti, R.; Foley, R. J.; Chornock, R.; Terreran, G.; Hiramatsu, D.; Newsome, M.; Padilla Gonzalez, E.; Pellegrino, C.; Howell, D. A.; Filippenko, A. V.; Anderson, J. P.; Angus, C. R.; Auchettl, K.; Bostroem, K. A.; Brink, T. G.; Cartier, R.; Coulter, D. A.; de Boer, T.; Drout, M. R.; Earl, N.; Ertini, K.; Farah, J. R.; Farias, D.; Gall, C.; Gao, H.; Gerlach, M. A.; Guo, F.; Haynie, A.; Hosseinzadeh, G.; Ibik, A. L.; Jha, S. W.; Jones, D. O.; Langeroodi, D.; Lebaron, N.; Magnier, E. A.; Piro, A. L.; Raimundo, S. I.; Rest, A.; Rest, S.; Rich, R. Michael; Rojas-Bravo, C.; Sears, H.; Taggart, K.; Villar, V. A.; Wainscoat, R. J.; Wang, X-f.; Wasserman, A. R.; Yan, S.; Yang, Y.; Zhang, J.; Zheng, W.
    We present ultraviolet/optical/near-infrared observations and modeling of Type II supernovae (SNe II) whose early time (delta(t) < 2 days) spectra show transient, narrow emission lines from shock ionization of confined (r < 10(15) cm) circumstellar material (CSM). The observed electron-scattering broadened line profiles (i.e., IIn-like) of H i, He i/ii, C iv, and N iii/iv/v from the CSM persist on a characteristic timescale (t(IIn)) that marks a transition to a lower-density CSM and the emergence of Doppler-broadened features from the fast-moving SN ejecta. Our sample, the largest to date, consists of 39 SNe with early time IIn-like features in addition to 35 "comparison" SNe with no evidence of early time IIn-like features, all with ultraviolet observations. The total sample includes 50 unpublished objects with a total of 474 previously unpublished spectra and 50 multiband light curves, collected primarily through the Young Supernova Experiment and Global Supernova Project collaborations. For all sample objects, we find a significant correlation between peak ultraviolet brightness and both t(II)n and the rise time, as well as evidence for enhanced peak luminosities in SNe II with IIn-like features. We quantify mass-loss rates and CSM density for the sample through the matching of peak multiband absolute magnitudes, rise times, t(IIn), and optical SN spectra with a grid of radiation hydrodynamics and non-local thermodynamic equilibrium radiative-transfer simulations. For our grid of models, all with the same underlying explosion, there is a trend between the duration of the electron-scattering broadened line profiles and inferred mass-loss rate: t(IIn) approximate to 3.8[M/ (0.01 M-circle dot yr(-1))] days.