Spectra of Supernovae in the Nebular Phase

Jerkstrand, A.

doi:10.1007/978-3-319-21846-5_29

Cited by 65 publications

(34 citation statements)

References 70 publications

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“…To estimate the length of time that the photosphere of SN 2018zd would remain optically thick, we use eq. 58 in Jerkstrand (2017). For a 6 M ejecta mass and a 1 foe explosion energy (reasonable for a low mass RSG exploding as a Fe core-collapse SN), we expect the ejecta to start to become optically thin at ≈ 200 d, consistent with when we begin to see a faster decay.…”

Section: Bolometric Luminosity and Nickel Masssupporting

confidence: 72%

How low can you go? SN 2018zd as a low-mass Fe core-collapse supernova

Callis¹,

Fraser²,

Pastorello³

et al. 2021

Preprint

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We present spectroscopy and photometry of SN 2018zd, a Type IIP core-collapse supernova with signatures of interaction with circumstantial material in its earliest spectra. High ionization lines, the earmark of shock breakout, are not seen in the earliest spectral epoch, and are only seen in a single spectrum at 4.9 d after explosion. The strength and brevity of these features imply a confined circumstellar material shell in the immediate vicinity of the progenitor. Once the narrow emission lines disappear, SN 2018zd evolves similarly to a Type IIP SN, although the blue colour and enhanced plateau magnitude of SN 2018zd suggests an additional source of luminosity throughout the plateau phase. While SN 2018zd has previously been proposed as an electron-capture SN, we suggest that it is an Fe core-collapse from a low mass red supergiant progenitor. Differences in interpretation for SN 2018zd arise in part due to the large uncertainty on the distance to the host-galaxy NGC 2146, which we re-derive here to be 15.6 +6.1 −3.0 Mpc. We find the ejected 56 Ni mass for SN 2018zd to be 0.017 M , significantly higher than models of ECSNe predict. We also find the Ni/Fe ratio in SN 2018zd to be much lower that would be expected for an ECSN.

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Section: Bolometric Luminosity and Nickel Masssupporting

confidence: 72%

How low can you go? SN 2018zd as a low-mass Fe core-collapse supernova

Callis¹,

Fraser²,

Pastorello³

et al. 2021

Preprint

View full text Add to dashboard Cite

show abstract

“…Although the uncertainties associated with the ejecta opacity become smaller as it dilutes, these are replaced by even larger uncertainties in calculating the nebular spectrum, due to the increasing importance of deviations from local thermodynamical equilibrium (see Ref. [21] for a review in the supernova context). Nevertheless, if one could measure the bolometric nebular emission, it should faithfully track the radioactive decay energy input.…”

mentioning

confidence: 99%

Fingerprints of Heavy-Element Nucleosynthesis in the Late-Time Lightcurves of Kilonovae

et al. 2019

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The kilonova emission observed following the binary neutron star merger event GW170817 provided the first direct evidence for the synthesis of heavy nuclei through the rapid neutron capture process (r-process). The late-time transition in the spectral energy distribution to near-infrared wavelengths was interpreted as indicating the production of lanthanide nuclei, with atomic mass number A > ∼ 140. However, compelling evidence for the presence of even heavier third-peak (A ≈ 195) rprocess elements (e.g., gold, platinum) or translead nuclei remains elusive. At early times (∼ days) most of the r-process heating arises from a large statistical ensemble of β-decays, which thermalize efficiently while the ejecta is still dense, generating a heating rate that is reasonably approximated by a single power-law. However, at later times of weeks to months, the decay energy input can also possibly be dominated by a discrete number of α-decays, 223 Ra (half-life t 1/2 = 11.43 d), 225 Ac (t 1/2 = 10.0 d, following the β-decay of 225 Ra with t 1/2 = 14.9 d), and the fissioning isotope 254 Cf (t 1/2 = 60.5 d), which liberate more energy per decay and thermalize with greater efficiency than beta-decay products. Late-time nebular observations of kilonovae which constrain the radioactive power provide the potential to identify signatures of these individual isotopes, thus confirming the production of heavy nuclei. In order to constrain the bolometric light to the required accuracy, multi-epoch and wide-band observations are required with sensitive instruments like the James Webb Space Telescope. In addition, by comparing the nuclear heating rate obtained with an abundance distribution that follows the Solar r abundance pattern, to the bolometric lightcurve of AT 2017gfo, we find that the yet-uncertain r abundance of 72 Ge plays a decisive role in powering the lightcurve, if one assumes that GW170817 has produced a full range of the Solar r abundances down to mass number A ∼ 70.

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“…However, if we consider the ratio after 200-300 days, the result implies a more massive helium core. Valenti et al (2014) and Terreran et al (2019), using a large sample of CC-SNe, found that this line ratio generally evolves with time, and Jerkstrand (2017) show that stripped-envelope models typically predict a declining ratio with time. Using their figure 13, the observed ratio of ∼1 at 300d most closely matches 3-4 M He core models, which would correspond to a M Z AM S 15 M progenitor (if its a IIb SN).…”

Section: [Ca Ii]/[o I] Ratiomentioning

confidence: 90%

“…where M( 56 Ni) is the mass of 56 Ni synthesised during the explosion. As the light curve tail does not follow the 56 Co decay, the gamma escapes needs to be considered (Clocchiatti & Wheeler 1997;Jerkstrand 2017) as follows:…”

Section: Bolometric Luminositymentioning

confidence: 99%

SN 2017ivv: two years of evolution of a transitional Type II supernova

Gutiérrez,

Pastorello,

Jerkstrand

et al. 2020

Preprint

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We present the photometric and spectroscopic evolution of the type II supernova (SN II) SN 2017ivv (also known as ASASSN-17qp). Located in an extremely faint galaxy (M r = −10.3 mag), SN 2017ivv shows an unprecedented evolution during the two years of observations. At early times, the light curve shows a fast rise (∼ 6 − 8 days) to a peak of M max g = −17.84 mag, followed by a very rapid decline of 7.94 ± 0.48 mag per 100 days in the V−band. The extensive photometric coverage at late phases shows that the radioactive tail has two slopes, one steeper than that expected from the decay of 56 Co (between 100 and 350 days), and another slower (after 450 days), probably produced by an additional energy source. From the bolometric light curve, we estimated that the amount of ejected 56 Ni is ∼ 0.059 ± 0.003 M . The nebular spectra of SN 2017ivv show a remarkable transformation that allows the evolution to be split into three phases: (1) Hα strong phase (< 200 days); (2) Hα weak phase (between 200 and 350 days); and (3) Hα broad phase (> 500 days). We find that the nebular analysis favours a binary progenitor and an asymmetric explosion. Finally, comparing the nebular spectra of SN 2017ivv to models suggests a progenitor with a zero-age main-sequence mass of 15 -17 M .

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Spectra of Supernovae in the Nebular Phase

Cited by 65 publications

References 70 publications

How low can you go? SN 2018zd as a low-mass Fe core-collapse supernova

How low can you go? SN 2018zd as a low-mass Fe core-collapse supernova

Fingerprints of Heavy-Element Nucleosynthesis in the Late-Time Lightcurves of Kilonovae

SN 2017ivv: two years of evolution of a transitional Type II supernova

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