SN 2018gj: A Short Plateau Type II Supernova with Persistent Blueshifted Ha Emission

Teja, Rishabh Singh; Singh, Avinash; Sahu, D. K.; Anupama, G. C.; Kumar, Brajesh; Nakaoka, Tatsuya; Kawabata, Koji S; Yamanaka, Masayuki; Takey, Ali; Kawabata, Miho

doi:10.3847/1538-4357/acdf5e

Cited by 6 publications

(14 citation statements)

References 145 publications

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“…Another notable feature is a rapid luminosity decline at the radioactive tail just after the plateau stage. At first glance both the short plateau and the early gamma-ray leakage suggest a low-mass ejecta that seems to be in line with the hydrodynamic modeling (Teja et al, 2023). Yet obvious dissimilarities between SN 2018gj and SN 2020jfo -longer plateau of the former (75 vs 60 d), higher plateau luminosity, Hα emission asymmetry, and early gamma-ray leakage -suggest that SN 2018gj is a special case and not just a twin of SN 2020jfo.…”

Section: Introductionsupporting

confidence: 60%

“…The type IIP supernova SN 2018gj in the galaxy NGC 6217 discovered by Wiggins (2018) and explored in detail by Teja et al (2023) is the short-plateau (∼75 d) object. Another notable feature is a rapid luminosity decline at the radioactive tail just after the plateau stage.…”

Section: Introductionmentioning

confidence: 99%

“…There are two additional important reasons for that. First, the previous hydrodynamic model of SN 2018gj requires 0.1 − 0.2 M ⊙ in the circumstellar (CS) shell to account for the early luminosity peak (Teja et al, 2023). Meanwhile, the issue of the CS matter density can be explored based on available spectra in a way similar to that of SN 2020jfo (Utrobin and Chugai, 2024), though with some correction.…”

Section: Introductionmentioning

confidence: 99%

“…Below we use the distance modulus µ = 31.46 ± 0.15 (D = 19.61 Mpc), the reddening E(B − V ) = 0.08 ± 0.02 mag, and the explosion date of JD 2458127.8 (Teja et al, 2023).…”

Section: Introductionmentioning

confidence: 99%

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Revisiting short-plateau SN 2018gj

Utrobin,

Chugai

2024

Astrophys Space Sci

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We present an alternative model of unusual type IIP SN 2018gj. Despite the short plateau and early gamma-rays escape seem to favor low-mass ejecta, our hydrodynamic model requires the large ejected mass (≈23 M⊙). The high ejecta velocity, we find from hydrogen lines in early spectra, turns out among crucial constraints on the hydrodynamic model. We recover the wind density that rules out a notable contribution of the circumstellar interaction to the bolometric luminosity. The early radioactive gamma-rays escape is found to be due to the high velocity of 56 Ni, whereas the asymmetry of the Hα emission is attributed to the asymmetry of the 56 Ni ejecta. The available sample of type IIP supernovae studied hydrodynamically in a uniform way indicates that the asymmetry of the 56 Ni ejecta is probably their intrinsic property. Hydrogen lines in early spectra of SN 2018gi and SN 2020jfo are found to imply a clumpy structure of the outer ejecta. With two already known similar cases of SN 2008in and SN 2012A we speculate that the clumpiness of the outer ejecta is inherent to type IIP supernovae related to the red supergiant explosion.

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Section: Introductionsupporting

confidence: 60%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Below we use the distance modulus µ = 31.46 ± 0.15 (D = 19.61 Mpc), the reddening E(B − V ) = 0.08 ± 0.02 mag, and the explosion date of JD 2458127.8 (Teja et al, 2023).…”

Section: Introductionmentioning

confidence: 99%

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Revisiting short-plateau SN 2018gj

Utrobin,

Chugai

2024

Astrophys Space Sci

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“…It was classified as a SN IIb (and possible II-P) by Bertrand (2018) and as a SN II by Kilpatrick et al (2018a). Teja et al (2023) conducted extensive photometric and spectroscopic monitoring of the SN. Previously unpublished early time photometric monitoring also exists from KAIT.…”

Section: Sn 2018gjmentioning

confidence: 99%

A Snapshot Survey of Nearby Supernovae with the Hubble Space Telescope

Baer-Way,

DeGraw,

Zheng

et al. 2024

ApJ

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Over recent decades, robotic (or highly automated) searches for supernovae (SNe) have discovered several thousand events, many of them in quite nearby galaxies (distances < 30 Mpc). Most of these SNe, including some of the best-studied events to date, were found before maximum brightness and have associated with them extensive follow-up photometry and spectroscopy. Some of these discoveries are so-called “SN impostors,” thought to be superoutbursts of luminous blue variable stars, although possibly a new, weak class of massive-star explosions. We conducted a Snapshot program with the Hubble Space Telescope (HST) and obtained images of the sites of 31 SNe and four impostors, to acquire late-time photometry through two filters. The primary aim of this project was to reveal the origin of any lingering energy for each event, whether it is the result of radioactive decay or, in some cases, ongoing late-time interaction of the SN shock with preexisting circumstellar matter, or the presence of a light echo. Alternatively, lingering faint light at the SN position may arise from an underlying stellar population (e.g., a host star cluster, companion star, or a chance alignment). The results from this study complement and extend those from Snapshot programs by various investigators in previous HST cycles.

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Intermediate-luminosity Type IIP SN 2021gmj: a low-energy explosion with signatures of circumstellar material

Murai,

Tanaka,

Kawabata

et al. 2024

Monthly Notices of the Royal Astronomical Society

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We present photometric, spectroscopic and polarimetric observations of the intermediate-luminosity Type IIP supernova (SN) 2021gmj from 1 to 386 days 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 supernovae: the optical spectra show narrow P-Cygni profiles, indicating a low expansion velocity. We estimate the progenitor mass to be about 12 $\rm M_{\odot }$ from the nebular spectrum and the 56Ni mass to be about 0.02 $\rm M_{\odot }$ 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.

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SN 2018gj: A Short Plateau Type II Supernova with Persistent Blueshifted Ha Emission

Cited by 6 publications

References 145 publications

Revisiting short-plateau SN 2018gj

Revisiting short-plateau SN 2018gj

A Snapshot Survey of Nearby Supernovae with the Hubble Space Telescope

Intermediate-luminosity Type IIP SN 2021gmj: a low-energy explosion with signatures of circumstellar material

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