A study of two Type IIb supernovae: SNe 2008aq and 2019gaf

ABSTRACT We present photometric and spectroscopic studies of two core-collapse supernovae (SNe) 2008aq and 2019gaf in the optical wavelengths. Light curve and spectral sequence of both the SNe are similar to those of other Type IIb SNe. The pre-maximum spectrum of SN 2008aq showed prominent H $\alpha$ lines, the He lines started appearing in the near maximum spectrum. The near maximum spectrum of SN 2019gaf shows shallow H $\alpha$ absorption and He lines with almost similar strength. Both the SNe show transition from hydrogen-dominated spectra to helium-dominated spectra within a month after maximum brightness. The velocity evolution of SN 2008aq matches well with those of other well-studied Type IIb SNe, while SN 2019gaf shows higher velocities. Close to maximum light, the H $\alpha$ and He i line velocities of SN 2019gaf are $\sim$ 2000 and $\sim$ 4000 km s$^{-1}$ higher than other well-studied Type IIb SNe. Semi-analytical modelling indicates SN 2019gaf to be a more energetic explosion with a smaller ejecta mass than SN 2008aq. The zero-age main-sequence (ZAMS) mass of the progenitor estimated using the nebular spectra of SN 2008aq ranges between 13 and 20 M$_\odot$, while for SN 2019gaf, the inferred ZAMS mass is between 13 and 25 M$_\odot$. The [O i] to [Ca ii] lines flux ratio favours a less massive progenitor star in a binary system for both the SNe.

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Journal
Monthly Notices of the Royal Astronomical Society
Published
2026-01-14
DOI
https://doi.org/10.1093/mnras/stag093
Primary Topic
Gamma-ray bursts and supernovae
Type
article
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article

A study of two Type IIb supernovae: SNe 2008aq and 2019gaf

Rishabh Singh Teja, Raya Dastidar, D. K. SAHU, Hyobin Im et al.
Monthly Notices of the Royal Astronomical Society
Gamma-ray bursts and supernovae
article

A study of two Type IIb supernovae: SNe 2008aq and 2019gaf

Rishabh Singh Teja, Raya Dastidar, D. K. SAHU, Hyobin Im, J. Burke, D. Hiramatsu, Mridweeka Singh, Kuntal Misra, Shubham Srivastav, Arti Joshi, G C Anupama, D Andrew Howell, Anjasha Gangopadhyay, K Azalee Bostroem, Curtis McCully
article en

Abstract

ABSTRACT We present photometric and spectroscopic studies of two core-collapse supernovae (SNe) 2008aq and 2019gaf in the optical wavelengths. Light curve and spectral sequence of both the SNe are similar to those of other Type IIb SNe. The pre-maximum spectrum of SN 2008aq showed prominent H $\alpha$ lines, the He lines started appearing in the near maximum spectrum. The near maximum spectrum of SN 2019gaf shows shallow H $\alpha$ absorption and He lines with almost similar strength. Both the SNe show transition from hydrogen-dominated spectra to helium-dominated spectra within a month after maximum brightness. The velocity evolution of SN 2008aq matches well with those of other well-studied Type IIb SNe, while SN 2019gaf shows higher velocities. Close to maximum light, the H $\alpha$ and He i line velocities of SN 2019gaf are $\sim$ 2000 and $\sim$ 4000 km s$^{-1}$ higher than other well-studied Type IIb SNe. Semi-analytical modelling indicates SN 2019gaf to be a more energetic explosion with a smaller ejecta mass than SN 2008aq. The zero-age main-sequence (ZAMS) mass of the progenitor estimated using the nebular spectra of SN 2008aq ranges between 13 and 20 M$_\odot$, while for SN 2019gaf, the inferred ZAMS mass is between 13 and 25 M$_\odot$. The [O i] to [Ca ii] lines flux ratio favours a less massive progenitor star in a binary system for both the SNe.

Monthly Notices of the Royal Astronomical SocietyVol. 546(2)
Hiroshima University (JP), Queen's University Belfast (GB), Las Cumbres Observatory Global Telescope Network (US), Indian Institute of Astrophysics (IN), University of California, Santa Barbara (US), Pontificia Universidad Católica de Chile (CL), Shanghai Jiao Tong University (CN), University of Washington (US), Korea Astronomy and Space Science Institute (KR), Brera Astronomical Observatory (IT), Aryabhatta Research Institute of Observational Sciences (IN), Clínica Las Condes (CL), Millennium Institute of Astrophysics (CL), Center for Astrophysics Harvard & Smithsonian (US), AlbaNova (SE), The NSF AI Institute for Artificial Intelligence and Fundamental Interactions (US), Korea University of Science and Technology (KR)
Openalex Percentile: Top 83%
Gamma-ray bursts and supernovae
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