A comparative analysis of type Ia supernovae 2018xx and 2019gbx^⋆

¹ Center for Astronomy and Space Sciences, China Three Gorges University, Yichang, 443000 PR China
e-mail: xyzeng2018@ctgu.edu.cn
² College of Science, China Three Gorges University, Yichang, 443000 PR China
³ Physics Department and Tsinghua Center for Astrophysics (THCA), Tsinghua University, Beijing, 100084 PR China
e-mail: wang_xf@mail.tsinghua.edu.cn
⁴ Beijing Planetarium, Beijing Academy of Science of Technology, Beijing, 100044 PR China
⁵ Department of Physics, University of California, Santa Barbara, CA, 93106-9530 USA
⁶ Las Cumbres Observatory, 6740 Cortona Drive Suite 102, Goleta, CA, 93117-5575 USA
⁷ Xinjiang Astronomical Observatory, Chinese Academy of Sciences, Urumqi, Xinjiang, 830011 PR China
⁸ School of Astronomy and Space Science, University of Chinese Academy of Sciences, Beijing, 100049 PR China
⁹ Yunnan Observatories (YNAO), Chinese Academy of Sciences, Kunming, 650216 PR China
¹⁰ Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, Kunming, 650216 PR China
¹¹ Center for Astronomical Mega-Science, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing, 100012 PR China
¹² Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA, 02138-1516 USA
¹³ The School of Physics and Astronomy, Tel Aviv University, Tel Aviv, 69978 Israel
¹⁴ Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012 PR China
¹⁵ George P. and Cynthia Woods Mitchell Institute for Fundamental Physics & Astronomy, Texas A&M University, Department of Physics and Astronomy, 4242 TAMU, College Station, TX, 77843 USA

Received: 16 September 2022
Accepted: 15 May 2023

Abstract

We present a comparative study of two nearby type Ia supernovae (SNe Ia), 2018xx and 2019gbx, that exploded in NGC 4767 and MCG-02-33-017 at a distance of 48 Mpc and 60 Mpc, respectively. The B-band light curve decline rate for SN 2018xx is estimated to be 1.48 ± 0.07 mag and for SN 2019gbx it is 1.37 ± 0.07 mag. Despite the similarities in photometric evolution, quasi-bolometric luminosity, and spectroscopy between these two SNe Ia, SN 2018xx has been found to be fainter by about ∼0.38 mag in the B-band and has a lower ⁵⁶Ni yield. Their host galaxies have similar metallicities at the SN location, indicating that the differences between these two SNe Ia may be associated with the higher progenitor metallicity of SN 2018xx. Further inspection of the near-maximum-light spectra has revealed that SN 2018xx has relatively strong absorption features near 4300 Å relative to SN 2019gbx. The application of the code TARDIS fitting to the above features indicates that the absorption features near 4300 Å appear to be related to not only Fe II/Mg II abundance but possibly to the other element abundances as well. Moreover, SN 2018xx shows a weaker carbon absorption at earlier times, which is also consistent with higher ejecta metallicity.