分类： 天文学 >> 天文学 提交时间： 2023-02-19
Danfeng Xiang
Xiaofeng Wang
Xinghan Zhang
Hanna Sai
Jujia Zhang
Thomas G. Brink
Alexei V. Filippenko
Jun Mo
Tianmeng Zhang
Zhihao Chen
Luc Dessart
Zhitong Li
Shengyu Yan
Sergei I. Blinnikov
Liming Rui
E. Baron
J. M. DerKacy
摘要： We present extensive optical/ultraviolet observations and modelling analysis for the nearby SN 1987A-like peculiar Type II supernova (SN) 2018hna. Both photometry and spectroscopy covered phases extending to $>$500 days after the explosion, making it one of the best-observed SN II of this subtype. SN 2018hna is obviously bluer than SN 1987A during the photospheric phase, suggesting higher photospheric temperature, which may account for weaker BaII $\mathrm{\lambda}$6142 lines in its spectra. Analysis of early-time temperature evolution suggests a radius of $\sim$45 $\mathrm{R_{\odot}}$ for the progenitor of SN 2018hna, consistent with a blue supergiant (BSG). By fitting the bolometric light curve with hydrodynamical models, we find that SN 2018hna has an ejecta mass of $\sim$(13.7--17.7) $\mathrm{M_{\odot}}$, a kinetic energy of $\sim$ (1.0--1.2) $\times 10^{51}$ erg, and a $^{56}$Ni mass of about 0.05 $\mathrm{M_{\odot}}$. Moreover, based on standard stellar evolution and the oxygen mass (0.44--0.73 $\mathrm{M_{\odot}}$) deduced from nebular [OI] lines, the progenitor of SN 2018hna is expected to have an initial main-sequence mass $<$16 $\mathrm{M_{\odot}}$. In principle, such a relatively low-mass star cannot end as a BSG just before core-collapse, except some unique mechanisms are involved, such as rapid rotation, restricted semiconvection, etc. On the other hand, binary scenario may be more favourable, like in the case of SN 1987A. While the much lower oxygen mass inferred for SN~2018hna may imply that its progenitor system also had much lower initial masses than that of SN 1987A.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Hanna Sai
Xiaofeng Wang
Nancy Elias-Rosa
Yi Yang
Jujia Zhang
Weili Lin
Jun Mo
Anthony L. Piro
Xiangyun Zeng
Reguitti Andrea
Peter Brown
Christopher R. Burns
Yongzhi Cai
Achille Fiore
Eric Y. Hsiao
Jordi Isern
K. Itagaki
Wenxiong Li
Zhitong Li
Priscila J. Pessi
摘要： Early-time radiative signals from type Ia supernovae (SNe Ia) can provide important constraints on the explosion mechanism and the progenitor system. We present observations and analysis of SN 2019np, a nearby SN Ia discovered within 1-2 days after the explosion. Follow-up observations were conducted in optical, ultraviolet, and near-infrared bands, covering the phases from $\sim-$16.7 days to $\sim$+367.8 days relative to its $B-$band peak luminosity. The photometric and spectral evolutions of SN 2019np resembles the average behavior of normal SNe Ia. The absolute B-band peak magnitude and the post-peak decline rate are $M_{\rm max}(B)=-19.52 \pm 0.47$mag and $\Delta m_{\rm15}(B) =1.04 \pm 0.04$mag, respectively. No Hydrogen line has been detected in the near-infrared and nebular-phase spectra of SN 2019np. Assuming that the $^{56}$Ni powering the light curve is centrally located, we find that the bolometric light curve of SN 2019np shows a flux excess up to 5.0% in the early phase compared to the radiative diffusion model. Such an extra radiation perhaps suggests the presence of an additional energy source beyond the radioactive decay of central nickel. Comparing the observed color evolution with that predicted by different models such as interactions of SN ejecta with circumstellar matter (CSM)/companion star, a double-detonation explosion from a sub-Chandrasekhar mass white dwarf (WD), and surface $^{56}$Ni mixing, the latter one is favored.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Danfeng Xiang
Xiaofeng Wang
Xinghan Zhang
Hanna Sai
Jujia Zhang
Thomas G. Brink
Alexei V. Filippenko
Jun Mo
Tianmeng Zhang
Zhihao Chen
Luc Dessart
Zhitong Li
Shengyu Yan
Sergei I. Blinnikov
Liming Rui
E. Baron
J. M. DerKacy
摘要： We present extensive optical/ultraviolet observations and modelling analysis for the nearby SN 1987A-like peculiar Type II supernova (SN) 2018hna. Both photometry and spectroscopy covered phases extending to $>$500 days after the explosion, making it one of the best-observed SN II of this subtype. SN 2018hna is obviously bluer than SN 1987A during the photospheric phase, suggesting higher photospheric temperature, which may account for weaker BaII $\mathrm{\lambda}$6142 lines in its spectra. Analysis of early-time temperature evolution suggests a radius of $\sim$45 $\mathrm{R_{\odot}}$ for the progenitor of SN 2018hna, consistent with a blue supergiant (BSG). By fitting the bolometric light curve with hydrodynamical models, we find that SN 2018hna has an ejecta mass of $\sim$(13.7--17.7) $\mathrm{M_{\odot}}$, a kinetic energy of $\sim$ (1.0--1.2) $\times 10^{51}$ erg, and a $^{56}$Ni mass of about 0.05 $\mathrm{M_{\odot}}$. Moreover, based on standard stellar evolution and the oxygen mass (0.44--0.73 $\mathrm{M_{\odot}}$) deduced from nebular [OI] lines, the progenitor of SN 2018hna is expected to have an initial main-sequence mass $<$16 $\mathrm{M_{\odot}}$. In principle, such a relatively low-mass star cannot end as a BSG just before core-collapse, except some unique mechanisms are involved, such as rapid rotation, restricted semiconvection, etc. On the other hand, binary scenario may be more favourable, like in the case of SN 1987A. While the much lower oxygen mass inferred for SN~2018hna may imply that its progenitor system also had much lower initial masses than that of SN 1987A.
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