Browsing by Author "Nagao, Takashi"
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Item Intermediate-luminosity Type IIP SN 2021gmj : a low-energy explosion with signatures of circumstellar material(Oxford University Press, 2024-03-01) Murai, Yuta; Tanaka, Masaomi; Kawabata, Miho; Taguchi, Kenta; Teja, Rishabh Singh; Nakaoka, Tatsuya; Maeda, Keiichi; Kawabata, Koji S.; Nagao, Takashi; Moriya, Takashi J.; Sahu, D. K.; Anupama, G. C.; Tominaga, Nozomu; Morokuma, Tomoki; Imazawa, Ryo; Inutsuka, Satoko; Isogai, Keisuke; Kasuga, Toshihiro; Kobayashi, Naoto; Kondo, Sohei; Maehara, Hiroyuki; Mori, Yuki; Niino, Yuu; Ogawa, Mao; Ohsawa, Ryou; Okumura, Shin Ichiro; Saito, Sei; Sako, Shigeyuki; Takahashi, Hidenori; Uno, Kohki; Yamanaka, Masayuki; Department of Electronics and Nanoengineering; Metsähovi Radio Observatory; Anne Lähteenmäki Group; Tohoku University; University of Hyogo; Kyoto University; Indian Institute of Astrophysics; Hiroshima University; National Astronomical Observatory of Japan; Chiba Institute of Technology; University of Tokyo; Japan Spaceguard Association; Kagoshima UniversityWe present photometric, spectroscopic, and polarimetric observations of the intermediate-luminosity Type IIP supernova (SN) 2021gmj from 1 to 386 d after the explosion. The peak absolute V-band magnitude of SN 2021gmj is −15.5 mag, which is fainter than that of normal Type IIP SNe. The spectral evolution of SN 2021gmj resembles that of other sub-luminous SNe: The optical spectra show narrow P-Cygni profiles, indicating a low expansion velocity. We estimate the progenitor mass to be about 12 M⊙ from the nebular spectrum and the 56Ni mass to be about 0.02 M⊙ from the bolometric light curve. We also derive the explosion energy to be about 3 × 1050 erg by comparing numerical light-curve models with the observed light curves. Polarization in the plateau phase is not very large, suggesting nearly spherical outer envelope. The early photometric observations capture the rapid rise of the light curve, which is likely due to the interaction with a circumstellar material (CSM). The broad emission feature formed by highly ionized lines on top of a blue continuum in the earliest spectrum gives further indication of the CSM at the vicinity of the progenitor. Our work suggests that a relatively low-mass progenitor of an intermediate-luminosity Type IIP SN can also experience an enhanced mass-loss just before the explosion, as suggested for normal Type IIP SNe.Item The metamorphosis of the Type Ib SN 2019yvr: late-time interaction(Oxford University Press, 2024-03-01) Ferrari, Lucía; Folatelli, Gastón; Kuncarayakti, Hanindyo; Stritzinger, Maximilian; Maeda, Keiichi; Bersten, Melina; Román Aguilar, Lili M.; Sáez, M. Manuela; Dessart, Luc; Lundqvist, Peter; Mazzali, Paolo; Nagao, Takashi; Ashall, Chris; Bose, Subhash; Brennan, Seán J.; Cai, Yongzhi; Handberg, Rasmus; Holmbo, Simon; Karamehmetoglu, Emir; Pastorello, Andrea; Reguitti, Andrea; Anderson, Joseph; Chen, Ting Wan; Galbany, Lluís; Gromadzki, Mariusz; Gutiérrez, Claudia P.; Inserra, Cosimo; Kankare, Erkki; Müller Bravo, Tomás E.; Mattila, Seppo; Nicholl, Matt; Pignata, Giuliano; Sollerman, Jesper; Srivastav, Shubham; Young, David R.; Department of Electronics and Nanoengineering; Metsähovi Radio Observatory; Anne Lähteenmäki Group; Consejo Nacional de Investigaciones Científicas y Técnicas; University of Turku; Aarhus University; Kyoto University; University of California, Berkeley; Institut d 'Astrophysique de Paris; Stockholm University; Max-Planck-Institut für Astrophysik; Virginia Polytechnic Institute and State University; Chinese Academy of Sciences; INAF - Osservatorio Astronomico di Padova; European Southern Observatory Santiago; National Central University; CSIC - Institute of Space Sciences; University of Warsaw; Cardiff University; Queen's University Belfast; Universidad de TarapacáWe present observational evidence of late-time interaction between the ejecta of the hydrogen-poor Type Ib supernova (SN) 2019yvr and hydrogen-rich circumstellar material (CSM), similar to the Type Ib SN 2014C. A narrow H α emission line appears simultaneously with a break in the light-curve decline rate at around 80–100 d after explosion. From the interaction delay and the ejecta velocity, under the assumption that the CSM is detached from the progenitor, we estimate the CSM inner radius to be located at ∼6.5–9.1 × 1015 cm. The H α emission line persists throughout the nebular phase at least up to +420 d post-explosion, with a full width at half maximum of ∼2000 km s−1. Assuming a steady mass-loss, the estimated mass-loss rate from the luminosity of the H α line is ∼3–7 × 10−5 M yr−1. From hydrodynamical modelling and analysis of the nebular spectra, we find a progenitor He-core mass of 3–4 M, which would imply an initial mass of 13–15 M. Our result supports the case of a relatively low-mass progenitor possibly in a binary system as opposed to a higher mass single star undergoing a luminous blue variable phase.