TY - JOUR
T1 - SN 2020jgb
T2 - A Peculiar Type Ia Supernova Triggered by a Helium-shell Detonation in a Star-forming Galaxy
AU - Liu, Chang
AU - Miller, Adam A.
AU - Polin, Abigail
AU - Nugent, Anya E.
AU - De, Kishalay
AU - Nugent, Peter E.
AU - Schulze, Steve
AU - Gal-Yam, Avishay
AU - Fremling, Christoffer
AU - Anand, Shreya
AU - Andreoni, Igor
AU - Blanchard, Peter
AU - Brink, Thomas G.
AU - Dhawan, Suhail
AU - Filippenko, Alexei V.
AU - Maguire, Kate
AU - Schweyer, Tassilo
AU - Sears, Huei
AU - Sharma, Yashvi
AU - Graham, Matthew J.
AU - Groom, Steven L.
AU - Hale, David
AU - Kasliwal, Mansi M.
AU - Masci, Frank J.
AU - Purdum, Josiah
AU - Racine, Benjamin
AU - Sollerman, Jesper
AU - Kulkarni, Shrinivas R.
PY - 2023/4/1
Y1 - 2023/4/1
N2 - The detonation of a thin (≲0.03 M ⊙) helium shell (He-shell) atop a ∼1 M ⊙ white dwarf (WD) is a promising mechanism to explain normal Type Ia supernovae (SNe Ia), while thicker He-shells and less massive WDs may explain some recently observed peculiar SNe Ia. We present observations of SN 2020jgb, a peculiar SN Ia discovered by the Zwicky Transient Facility (ZTF). Near maximum brightness, SN 2020jgb is slightly subluminous (ZTF g-band absolute magnitude −18.7 mag ≲ M g ≲ −18.2 mag depending on the amount of host-galaxy extinction) and shows an unusually red color (0.2 mag ≲ g ZTF − r ZTF ≲ 0.4 mag) due to strong line-blanketing blueward of ∼5000 Å. These properties resemble those of SN 2018byg, a peculiar SN Ia consistent with an He-shell double detonation (DDet) SN. Using detailed radiative transfer models, we show that the optical spectroscopic and photometric evolution of SN 2020jgb is broadly consistent with a ∼0.95-1.00 M ⊙ (C/O core + He-shell) progenitor ignited by a ≳0.1 M ⊙ He-shell. However, one-dimensional radiative transfer models without non-local-thermodynamic-equilibrium treatment cannot accurately characterize the line-blanketing features, making the actual shell mass uncertain. We detect a prominent absorption feature at ∼1 μm in the near-infrared (NIR) spectrum of SN 2020jgb, which might originate from unburnt helium in the outermost ejecta. While the sample size is limited, we find similar 1 μm features in all the peculiar He-shell DDet candidates with NIR spectra obtained to date. SN 2020jgb is also the first peculiar He-shell DDet SN discovered in a star-forming dwarf galaxy, indisputably showing that He-shell DDet SNe occur in both star-forming and passive galaxies, consistent with the normal SN Ia population.
AB - The detonation of a thin (≲0.03 M ⊙) helium shell (He-shell) atop a ∼1 M ⊙ white dwarf (WD) is a promising mechanism to explain normal Type Ia supernovae (SNe Ia), while thicker He-shells and less massive WDs may explain some recently observed peculiar SNe Ia. We present observations of SN 2020jgb, a peculiar SN Ia discovered by the Zwicky Transient Facility (ZTF). Near maximum brightness, SN 2020jgb is slightly subluminous (ZTF g-band absolute magnitude −18.7 mag ≲ M g ≲ −18.2 mag depending on the amount of host-galaxy extinction) and shows an unusually red color (0.2 mag ≲ g ZTF − r ZTF ≲ 0.4 mag) due to strong line-blanketing blueward of ∼5000 Å. These properties resemble those of SN 2018byg, a peculiar SN Ia consistent with an He-shell double detonation (DDet) SN. Using detailed radiative transfer models, we show that the optical spectroscopic and photometric evolution of SN 2020jgb is broadly consistent with a ∼0.95-1.00 M ⊙ (C/O core + He-shell) progenitor ignited by a ≳0.1 M ⊙ He-shell. However, one-dimensional radiative transfer models without non-local-thermodynamic-equilibrium treatment cannot accurately characterize the line-blanketing features, making the actual shell mass uncertain. We detect a prominent absorption feature at ∼1 μm in the near-infrared (NIR) spectrum of SN 2020jgb, which might originate from unburnt helium in the outermost ejecta. While the sample size is limited, we find similar 1 μm features in all the peculiar He-shell DDet candidates with NIR spectra obtained to date. SN 2020jgb is also the first peculiar He-shell DDet SN discovered in a star-forming dwarf galaxy, indisputably showing that He-shell DDet SNe occur in both star-forming and passive galaxies, consistent with the normal SN Ia population.
UR - http://www.scopus.com/inward/record.url?scp=85151814400&partnerID=8YFLogxK
U2 - 10.3847/1538-4357/acbb5e
DO - 10.3847/1538-4357/acbb5e
M3 - Article
AN - SCOPUS:85151814400
SN - 0004-637X
VL - 946
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 2
M1 - 83
ER -