Broad emission lines from the opaque electron-scattering environment of SN 1998S

(Fig. 1). The first BB temperature estimate was obtained via careful extrapolation of the UVOT UV M2 and P60 g + i light curves back to the first P48 (detection) point (see inset of Fig. 1 and text for details). The earlytime BB temperature estimates, within the first half day after explosion, are also in agreement with our temperature estimates from the modeling of the early Keck spectra (Fig. 4), showing the highly ionised emission lines at temperatures > ∼ 50 kK. The shaded region and the solid black line (a running mean of the region) denote bolometric luminosity estimates based on the multiband photometry ( Fig. 1) according to three methods used to calculate the total flux from the SED: interpolation, order-4 polynomial fit, and BB fits. The top end of the shaded region can be regarded as our best lower limit on the real bolometric luminosity, based on the photometric observations. The red triangles denote a (more conservative) lower limit on the bolometric luminosity obtained from our spectra (Fig. 2, Fig. 3), beginning with the early set of 4 Keck spectra at < ∼ 10 hr after explosion and ending with our latest spectrum at 57.2days. The blue triangles show the luminosity as obtained by our best BB temperature and radius estimates (Fig. 4), L = 4πR 2 σT 4 ; the luminosity in the first point, at ∼ 3.8 hr after explosion, exceeds 10 44 erg s −1 .

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“…6. We note the remarkable resemblance of this proposed CSM configuration to the density profile calculated by ref 29. (Fig.…”

supporting

confidence: 79%

Confined dense circumstellar material surrounding a regular type II supernova

et al. 2017

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“…This profile may be also interpreted as a narrow core with broad wings resulting from multiple scattering events with thermal electrons, an escape mechanism for line photons favoured by the small photospheric velocity observed for SN 2008S at all phases (Dessart et al 2009). The electron scattering in a dense (Thomson optical depth of ∼3–4) CS shell lying beyond the SN photosphere was suggested by Chugai (2001) as an explanation for the very broad wings of Hα in SN 1998S. We compare the Hα profiles of SN 1998S and SN 2008S in Fig.…”

Section: Spectroscopic Data Reduction and Analysismentioning

confidence: 90%

“…The high density of the CS shell in the case of SN 1998S implies that a CDS forms at the interface of SN ejecta and the CSM. The absence of broad P‐Cygni profiles was explained with obscuration by the CDS (Chugai 2001). Fassia et al (2001) showed that absorption troughs appeared in the spectra of SN 1998S after only 12 d, and suggested that the SN ejecta had over‐run the inner CS by that point.…”

Section: The Nature Of Sn 2008smentioning

confidence: 99%

“…SN 1998S and SN 1979C have been suggested to be the results of explosions of a red supergiant with an extended envelope, R ∼ (1–10) × 10 3 R ⊙ , and a moderate mass of ejecta ∼5 M ⊙ . Chugai (2001) suggested also that the origin of the CS shell around SN 1998S may be a violent mass loss during the Ne and O burning in cores of ∼11 M ⊙ . The mass‐loss rate of the progenitor by optical, radio and X‐ray estimates is about 1–5 × 10 −4 M ⊙ yr −1 .…”

Section: The Nature Of Sn 2008smentioning

confidence: 99%

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SN 2008S: an electron-capture SN from a super-AGB progenitor?

Botticella

Pastorello

Smartt

et al. 2009

Monthly Notices of the Royal Astronomical Society

164

185

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We present comprehensive photometric and spectroscopic observations of the faint transient SN 2008S discovered in the nearby galaxy NGC 6946. SN 2008S exhibited slow photometric evolution and almost no spectral variability during the first nine months, implying a long photon diffusion time and a high-density circumstellar medium. Its bolometric luminosity ( 10 41 erg s −1 at peak) is low with respect to most core-collapse supernovae but is comparable to the faintest Type II-P events. Our quasi-bolometric light curve extends to 300 d and shows a tail phase decay rate consistent with that of 56 Co. We propose that this is evidence for an explosion and formation of 56 Ni (0.0014 ± 0.0003 M ). Spectra of SN 2008S show intense emission lines of Hα, [Ca II] doublet and Ca II near-infrared (NIR) triplet, all without obvious P-Cygni absorption troughs. The large mid-infrared (MIR) flux detected shortly after explosion can be explained by a light echo from pre-existing dust. The late NIR flux excess is plausibly due to a combination of warm newly formed ejecta dust together with shock-heated dust in the circumstellar environment. We reassess the progenitor object detected previously in Spitzer archive images, supplementing this discussion with a model of the MIR spectral energy distribution. This supports the idea of a dusty, optically thick shell around SN 2008S with an inner radius of nearly 90 AU and outer radius of 450 AU, and an inferred heating source

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“…Dust formation in the ejecta can be ruled out for the early epochs (26- Alternatively, the photosphere is in front of the forward shock and the emission line velocities do not represent physical motion of the shock but are rather caused by Thompson electron scattering (13,40,52). As the photosphere recedes it will be located behind the forward shock Figure 4).…”

Section: Our High-resolution Data Set Clearly Shows That the Intermedmentioning

confidence: 99%

Rapid formation of large dust grains in the luminous supernova 2010jl

Gall

Hjorth

Watson

et al. 2014

Nature

219

311

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The origin of dust in galaxies is still a mystery (1, 2, 3, 4). The majority of the refractory elements are produced in supernova explosions but it is unclear how and where dust grains condense and grow, and how they avoid destruction in the harsh environments of star-forming 3 Figure 3 shows the resulting confidence interval for the two parameters a max and α around the best fit values of a min = 0.001 µm, a max = 4.2 µm and α = 3.6. It is evident that only size distributions extending to grain radii that are significantly larger than that of MW interstellar medium (21, 22) dust ( 0.25 µm) can reproduce the supernova extinction curve (Figure 2). The 2 σ lower limit on the maximum grain size is a max > 0.7 µm. We cannot perform a similar analysis of the late epoch because the intrinsic line profile at this epoch is unknown and likely highly affected by extinction (13). However, we note that the blueshift velocities change only marginally with wavelength (Extended Data Figure 6), suggestive of large grains also at this epoch. Figure 4 illustrates the continuous build-up of dust as a function of time. The increasing attenuation of the lines is accompanied by increasing emission in the near-infrared (NIR) spectra, from a slight excess over a supernova blackbody fit at early times to total dominance at the late epoch. We fitted the spectra with black bodies which for the NIR excess yield a constant blackbody radius of (1.0 ± 0.2) × 10 16 cm at the early epochs, and a temperature that declines from ∼ 2,300 K to ∼ 1,600 K from day 26 onwards. At the late epoch, we obtain a black-body radius of (5.7 ± 0.2) × 10 16 cm and a temperature of ∼ 1,100 K. The high temperatures detected at the early epochs suggest that the NIR excess is due to thermal emission from carbonaceous dust, rather than silicate dust, which has a lower condensation temperature of ∼ 1, 500 K (1). The high temperatures rule out suggestions that the NIR emission is due to pre-existing dust or a dust echo (11) (Figure 1), the accelerated dust formation occurring at later times ( Figure 4) and at larger radius is possibly facilitated by the bulk ejecta material, which travels on average at a velocity of ∼ 7, 500 km s −1 at early epochs (Extended Data Figure 4).Our detection of large grains soon after the supernova explosion suggests a remarkably rapid and efficient mechanism for dust nucleation and growth. The underlying physics is poorly understood but may involve a two-stage process governed by early dust formation in a cool, dense shell, 5 followed by accelerated dust formation involving ejecta material. For Type IIP supernovae, the growth of dust grains can be sustained up to 5 years past explosion (25). The dense CSM around Type IIn supernovae may provide conditions to facilitate dust growth beyond that. The process appears generic, in that other Type IIn supernovae like SN 1995N, SN 1998S, SN 2005ip, and SN 2006jd exhibited similar observed NIR properties (8, 10, 26, 27) and growing dust masses, consistent with the trend revealed here for SN 2010...

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Broad emission lines from the opaque electron-scattering environment of SN 1998S

Cited by 12 publications

References 20 publications

Confined dense circumstellar material surrounding a regular type II supernova

Confined dense circumstellar material surrounding a regular type II supernova

SN 2008S: an electron-capture SN from a super-AGB progenitor?

Rapid formation of large dust grains in the luminous supernova 2010jl

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