A year-long plateau in the late-time near-infrared light curves of type Ia supernovae

Graur, Or; Maguire, K.; Ryan, Russell E.; Nicholl, M.; Avelino, Arturo; Riess, Adam G.; Shingles, Luke J.; Seitenzahl, Ivo R.; Fisher, Robert

doi:10.1038/s41550-019-0901-1

Cited by 22 publications

(19 citation statements)

References 76 publications

(103 reference statements)

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“…The [Ca II] feature generally exhibits a similar decline in flux but shows strong variations, especially at ≈ 500 − 600 days after t max when the Fe-region changes its decline rate. This general time period agrees with the end of the nebular-phase NIR plateau discovered by Graur et al (2020) and coincides with a distinct change in the optical-to-NIR flux ratio (Maguire et al 2016;Dimitriadis et al 2017;Graur et al 2020). We briefly discuss the potential of [Ca II] as a diagnostic feature for the ejecta in §4.…”

Section: The 7300 å Featuresupporting

confidence: 78%

A Rapid Ionization Change in the Nebular-Phase Spectra of the Type Ia SN 2011fe

Tucker,

Ashall,

Shappee

et al. 2021

Preprint

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We present three new spectra of the nearby Type Ia supernova (SN Ia) 2011fe covering ≈ 480 − 850 days after maximum light and show that the ejecta undergoes a rapid ionization shift at ∼ 500 days after explosion. The prominent [Fe III] emission lines at ≈ 4600 Å are replaced with the permitted Fe I+Fe II blends at ∼ 4400 Å and ∼ 5400 Å. The ≈ 7300 Å feature, which is produced by [Fe II] +[Ni II] at 400 days after explosion, is replaced by broad (≈ ±15 000 km s −1 ) symmetric [Ca II] emission. The change in emission characteristics is likely due to the temperature in the inner ejecta dropping below the level needed to populate the high-ionization Fe III transitions. This ionization shift corresponds to a distinct temperature and density in the ejecta and may be useful as a probe of the ejecta's temporal evolution. Models predict this ionization transition occurring ∼ 100 days later than what is observed which we attribute to clumping in the ejecta. Finally, we discuss the reliability of [Ca II] as an ejecta diagnostic feature.

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Section: The 7300 å Featuresupporting

confidence: 78%

A Rapid Ionization Change in the Nebular-Phase Spectra of the Type Ia SN 2011fe

Tucker,

Ashall,

Shappee

et al. 2021

Preprint

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“…Both the +1000day theoretical spectrum from Fransson & Jerkstrand (2015) and the optical + NIR photometry from Shappee et al ( 2017) predict a NIR fraction 2 of F NIR ≈ 35% which we adopt in our analysis. The NIR fraction is roughly constant after the redistribution of flux at ≈ 500 days after t max (Dimitriadis et al 2017;Maguire et al 2018;Graur et al 2020).…”

Section: Constructing the Pseudo-bolometric Light Curvementioning

confidence: 95%

The Whisper of a Whimper of a Bang: 2400 Days of the Type Ia SN 2011fe Reveals the Decay of $^{55}$Fe

Tucker¹,

Shappee²,

Kochanek³

et al. 2021

Preprint

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We analyze new multi-filter Hubble Space Telescope (HST) photometry of the normal Type Ia supernova (SN Ia) 2011fe out to ≈ 2400 days after maximum light, the latest observations to-date of a SN Ia. We model the pseudo-bolometric light curve with a simple radioactive decay model and find energy input from both 57 Co and 55 Fe are needed to power the late-time luminosity. This is the first detection of 55 Fe in a SN Ia. We consider potential sources of contamination such as a surviving companion star or delaying the deposition timescale for 56 Co positrons but these scenarios are ultimately disfavored. The relative isotopic abundances place direct constraints on the burning conditions experienced by the white dwarf and require a central density of ρ c ∼ 3 × 10 8 g cm −3 . Only 2 classes of explosion models are currently consistent with all observations of SN 2011fe: 1) the delayed detonation of a low-ρ c , near-M Ch (1.2 − 1.3M ) WD, or 2) a sub-M Ch (1.0 − 1.1 M ) WD experiencing a thin-shell double detonation.

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“…Late-time observations of thermonuclear explosions suggest that positrons escape from SN Ia ejecta after a few hundred days (Milne et al 1999(Milne et al , 2001(Milne et al , 2004. This result is, however, uncertain because of the difficulty of inferring the bolometric luminosity of SNe at such late times and because of the uncertain decaying isotope at the origin of the SN luminosity, such as the relative importance of the 57 Ni decay chain relative to that of 56 Ni (Graur et al 2016(Graur et al , 2020.…”

Section: The Positron Contribution To the Sn Luminositymentioning

confidence: 99%

Nebular phase properties of supernova Ibc from He-star explosions

Hillier

Sukhbold

Woosley

et al. 2021

A&A

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Following our recent work on Type II supernovae (SNe), we present a set of 1D nonlocal thermodynamic equilibrium radiative transfer calculations for nebular-phase Type Ibc SNe starting from state-of-the-art explosion models with detailed nucleosynthesis. Our grid of progenitor models is derived from He stars that were subsequently evolved under the influence of wind mass loss. These He stars, which most likely form through binary mass exchange, synthesize less oxygen than their single-star counterparts with the same zero-age main sequence (ZAMS) mass. This reduction is greater in He-star models evolved with an enhanced mass loss rate. We obtain a wide range of spectral properties at 200 d. In models from He stars with an initial mass > 6 M⊙, the [O I] λλ 6300, 6364 is of a comparable or greater strength than [Ca II] λλ 7291, 7323 – the strength of [O I] λλ 6300, 6364 increases with the He-star initial mass. In contrast, models from lower mass He stars exhibit a weak [O I] λλ 6300, 6364, strong [Ca II] λλ 7291, 7323, and also strong N II lines and Fe II emission below 5500 Å. The ejecta density, which is modulated by the ejecta mass, the explosion energy, and clumping, has a critical impact on gas ionization, line cooling, and spectral properties. We note that Fe II dominates the emission below 5500 Å and is stronger at earlier nebular epochs. It ebbs as the SN ages, while the fractional flux in [O I] λλ 6300, 6364 and [Ca II] λλ 7291, 7323 increases with a similar rate as the ejecta recombine. Although the results depend on the adopted wind mass loss rate and pre-SN mass, we find that He-stars of 6–8 M⊙ initially (ZAMS mass of 23–28 M⊙) match the properties of standard SNe Ibc adequately. This finding agrees with the offset in progenitor masses inferred from the environments of SNe Ibc relative to SNe II. Our results for less massive He stars are more perplexing since the predicted spectra are not seen in nature. They may be missed by current surveys or associated with Type Ibn SNe in which interaction power dominates over decay power.

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A year-long plateau in the late-time near-infrared light curves of type Ia supernovae

Cited by 22 publications

References 76 publications

A Rapid Ionization Change in the Nebular-Phase Spectra of the Type Ia SN 2011fe

A Rapid Ionization Change in the Nebular-Phase Spectra of the Type Ia SN 2011fe

The Whisper of a Whimper of a Bang: 2400 Days of the Type Ia SN 2011fe Reveals the Decay of $^{55}$Fe

Nebular phase properties of supernova Ibc from He-star explosions

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