SN 2016dsg: A Thermonuclear Explosion Involving a Thick Helium Shell

Dong, Yize; Valenti, S.; Polin, Abigail; Boyle, Aoife; Flörs, Andreas; Vogl, C.; Kerzendorf, Wolfgang; Sand, David J.; Wyrzykowski, Ł.; Bostroem, K. A.; McCully, C.; Andrew, Jennifer S.; Benettii, Stefano; Blondin, S; Galbany, L.; Gromadzki, M.; Hosseinzadeh, G.; Howell, D. A.; Inserra, C.; Jencson, J.; Lundquist, M.; Lyman, J. D.; Magee, M.; Maguire, Kate; Meza, N.; Srivastav, Shubham; Taubenberger, S.; Terwel, J.; Wyatt, S.; Young, D. R.

doi:10.3847/1538-4357/ac75eb

Cited by 12 publications

(14 citation statements)

References 83 publications

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“…These events are faint, red, and show strong line-blanketing in spectra at maximum light. A tentative detection of unburnt helium in SN 2016dsg was also reported by Dong et al (2022a). We refer to these events as peculiar He-shell DDet SNe.…”

Section: Introductionsupporting

confidence: 65%

“…SN 2019ofm has a large projected offset (∼11 kpc) but is still on a spiral arm, as shown in its DECaLS image (Dey et al 2019). Other objects, including the recently reported SN 2016dsg and OGLE-2013-SN-079 (Dong et al 2022a), show large projected host offsets (10 kpc) and lie in the galaxy outskirts, which usually indicates an old stellar population origin.…”

Section: The Host Environment Of He-shell Ddet Snementioning

confidence: 84%

“…The spectrum of SN 2018byg is originally noisy, so it is binned with a size of 10 Å. For SN 2016dsg, we show the spectrum smoothed with a Savitzky-Golay filter in Dong et al (2022a). 35 We also note that a similar 1 μm feature is detected in another possibly relevant object, SN 2012hn (Valenti et al 2014), in an NIR spectrum obtained at +25 days.…”

Section: The Host Environment Of He-shell Ddet Snementioning

confidence: 89%

“…SN 2018byg (De et al 2019) is a prototype of this subclass. Other candidates include OGLE-2013-SN-079 (Inserra et al 2015), SN 2016dsg (Dong et al 2022a), SN 2016hnk (Jacobson-Galán et al 2020; see, Galbany et al 2019), and SN 2019ofm ).…”

Section: Introductionmentioning

confidence: 99%

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SN 2020jgb: A Peculiar Type Ia Supernova Triggered by a Helium-shell Detonation in a Star-forming Galaxy

Liu

Miller

Polin

et al. 2023

ApJ

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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.

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Section: Introductionsupporting

confidence: 65%

Section: The Host Environment Of He-shell Ddet Snementioning

confidence: 84%

Section: The Host Environment Of He-shell Ddet Snementioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

SN 2020jgb: A Peculiar Type Ia Supernova Triggered by a Helium-shell Detonation in a Star-forming Galaxy

Liu

Miller

Polin

et al. 2023

ApJ

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“…Similarly Shen et al (2021b) found that their minimal He shell mass models were able to reproduce normal SNe Ia. Double detonation models have been suggested to explain a number of peculiar SNe Ia (Inserra et al 2015;Jiang et al 2017;De et al 2019;Dong et al 2022), which showed unusually red colours, early flux excesses and Ti absorption features. The red colours can be explained by absorption at blue wavelengths by the products of the helium shell detonation, as can the Ti absorption features (e.g.…”

Section: Introductionmentioning

confidence: 95%

Double detonations: variations in Type Ia supernovae due to different core and He shell masses – II. Synthetic observables

Collins

Gronow

Röpke

2022

Monthly Notices of the Royal Astronomical Society

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Double detonations of sub-Chandrasekhar mass white dwarfs are a promising explosion scenario for Type Ia supernovae, whereby a detonation in a surface helium shell triggers a secondary detonation in a carbon-oxygen core. Recent work has shown that low mass helium shell models reproduce observations of normal SNe Ia. We present 3D radiative transfer simulations for a suite of 3D simulations of the double detonation explosion scenario for a range of shell and core masses. We find light curves broadly able to reproduce the faint end of the width-luminosity relation shown by SNe Ia, however, we find that all of our models show extremely red colours, not observed in normal SNe Ia. This includes our lowest mass helium shell model. We find clear Ti ii absorption features in the model spectra, which would lead to classification as peculiar SNe Ia, as well as line blanketing in some lines of sight by singly ionised Cr and Fe-peak elements. Our radiative transfer simulations show that these explosion models remain promising to explain peculiar SNe Ia. Future full non-LTE simulations may improve the agreement of these explosion models with observations of normal SNe Ia.

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Helium as a signature of the double detonation in Type Ia supernovae

Collins

Shingles

Gronow

et al. 2023

Monthly Notices of the Royal Astronomical Society

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The double detonation is a widely discussed mechanism to explain Type Ia supernovae from explosions of sub-Chandrasekhar mass white dwarfs. In this scenario, a helium detonation is ignited in a surface helium shell on a carbon/oxygen white dwarf, which leads to a secondary carbon detonation. Explosion simulations predict high abundances of unburnt helium in the ejecta, however, radiative transfer simulations have not been able to fully address whether helium spectral features would form. This is because helium can not be sufficiently excited to form spectral features by thermal processes, but can be excited by collisions with non-thermal electrons, which most studies have neglected. We carry out a full non-local thermodynamic equilibrium (non-LTE) radiative transfer simulation for an instance of a double detonation explosion model, and include a non-thermal treatment of fast electrons. We find a clear He i λ10830 feature which is strongest in the first few days after explosion and becomes weaker with time. Initially this feature is blended with the Mg ii λ10927 feature but over time separates to form a secondary feature to the blue wing of the Mg ii λ10927 feature. We compare our simulation to observations of iPTF13ebh, which showed a similar feature to the blue wing of the Mg ii λ10927 feature, previously identified as C i. Our simulation shows a good match to the evolution of this feature and we identify it as high velocity He i λ10830. This suggests that He i λ10830 could be a signature of the double detonation scenario.

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SN 2016dsg: A Thermonuclear Explosion Involving a Thick Helium Shell

Cited by 12 publications

References 83 publications

SN 2020jgb: A Peculiar Type Ia Supernova Triggered by a Helium-shell Detonation in a Star-forming Galaxy

SN 2020jgb: A Peculiar Type Ia Supernova Triggered by a Helium-shell Detonation in a Star-forming Galaxy

Double detonations: variations in Type Ia supernovae due to different core and He shell masses – II. Synthetic observables

Helium as a signature of the double detonation in Type Ia supernovae

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