Examinando por Autor "Paraskeva, E."

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    Close, bright, and boxy: the superluminous SN 2018hti
    (Oxford University Press, 2022-05-01) Fiore, A.; Benetti, S.; Nicholl, M.; Reguitti, A.; Cappellaro, E.; Campana, S.; Bose, S.; Paraskeva, E.; Berger, E.; Bravo, T.M.; Burke, J.; Cai, Y.-Z.; Chen, T.-W.; Chen, P.; Ciolfi, R.; Dong, S.; Gomez, S.; Gromadzki, M.; Gutiérrez, C.P.; Hiramatsu, D.; Hosseinzadeh, G.; Howell, D.A.; Jerkstrand, A.; Kankare, E.; Kozyreva, A.; Maguire, K.; McCully, C.; Ochner, P.; Pellegrino, C.; Pignata, G.; Post, R.S.; Elias-Rosa, N.; Shahbandeh, M.; Schuldt, S.; Thomas, B.P.; Tomasella, L.; Vinkó, J.; Vogl, C.; Wheeler, J.C.; Young, D.R.
    SN 2018hti was a very nearby (z = 0.0614) superluminous supernova with an exceedingly bright absolute magnitude of -21.7 mag in r band at maximum. The densely sampled pre-maximum light curves of SN 2018hti show a slow luminosity evolution and constrain the rise time to ∼50 rest-frame d. We fitted synthetic light curves to the photometry to infer the physical parameters of the explosion of SN 2018hti for both the magnetar and the CSM-interaction scenarios. We conclude that one of two mechanisms could be powering the luminosity of SN 2018hti; interaction with ∼10 M⊙ of circumstellar material or a magnetar with a magnetic field of Bp∼1.3 × 1013 G, and initial period of Pspin∼1.8 ms. From the nebular spectrum modelling we infer that SN 2018hti likely results from the explosion of a ∼40M⊙ progenitor star. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.
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    SN 2020acat: an energetic fast rising Type IIb supernova
    (Oxford University Press, 2022-07-01) Medler, K.; Mazzali, P.A.; Teffs, J.; Ashall, C.; Anderson, J.P.; Arcavi, I.; Benetti, S.; Bostroem, K.A.; Burke, J.; Cai, Y.-Z.; Charalampopoulos, P.; Elias Rosa, N.; Ergon, M.; Galbany, L.; Gromadzki, M.; Hiramatsu, D.; Howell, D.A.; Inserra, C.; Lundqvist, P.; McCully, C.; Müller Bravo, T.; Newsome, M.; Nicholl, M.; Gonzalez, E. Padilla; Paraskeva, E.; Pastorello, A.; Pellegrino, C.; Pessi, P.J.; Reguitti, A.; Reynolds, T.M.; Roy, R.; Terreran, G.; Tomasella, L.; Young, D.R.
    The ultraviolet (UV) and near-infrared (NIR) photometric and optical spectroscopic observations of SN 2020acat covering ∼250 d after explosion are presented here. Using the fast rising photometric observations, spanning from the UV to NIR wavelengths, a pseudo-bolometric light curve was constructed and compared to several other well-observed Type IIb supernovae (SNe IIb). SN 2020acat displayed a very short rise time reaching a peak luminosity of Log10(L) = 42.49 ± 0.17 erg s-1 in only ∼14.6 ± 0.3 d. From modelling of the pseudo-bolometric light curve, we estimated a total mass of 56Ni synthesized by SN 2020acat of MNi = 0.13 ± 0.03 M⊙, with an ejecta mass of Mej = 2.3 ± 0.4 M⊙ and a kinetic energy of Ek = 1.2 ± 0.3 × 1051 erg. The optical spectra of SN 2020acat display hydrogen signatures well into the transitional period (≳ 100 d), between the photospheric and the nebular phases. The spectra also display a strong feature around 4900 Å that cannot be solely accounted for by the presence of the Fe ii 5018 line. We suggest that the Fe ii feature was augmented by He i 5016 and possibly by the presence of N ii 5005. From both photometric and spectroscopic analysis, we inferred that the progenitor of SN 2020acat was an intermediate-mass compact star with an MZAMS of 15-20 M⊙. © 2022 The Author(s).