The opacity of expanding media - The effect of spectral lines

Karp, Alan H.; Lasher, Gordon; Chan, Kalok; Salpeter, E. E.

doi:10.1086/155241

Cited by 160 publications

(129 citation statements)

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“…These are reasonable estimates at early times, although free-free absorption may contribute as well (Rogers & Iglesias 1992). At later times recombination reduces the electron scattering opacity but line blocking makes significant contributions (Karp et al 1977). …”

Section: A23 Physical Approximationssupporting

confidence: 53%

A comparative study of Type II-P and II-L supernova rise times as exemplified by the case of LSQ13cuw

Gáll

Polshaw

Kotak

et al. 2015

A&A

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We report on our findings based on the analysis of observations of the Type II-L supernova LSQ13cuw within the framework of currently accepted physical predictions of core-collapse supernova explosions. LSQ13cuw was discovered within a day of explosion, hitherto unprecedented for Type II-L supernovae. This motivated a comparative study of Type II-P and II-L supernovae with relatively well-constrained explosion epochs and rise times to maximum (optical) light. From our sample of twenty such events, we find evidence of a positive correlation between the duration of the rise and the peak brightness. On average, SNe II-L tend to have brighter peak magnitudes and longer rise times than SNe II-P. However, this difference is clearest only at the extreme ends of the rise time versus peak brightness relation. Using two different analytical models, we performed a parameter study to investigate the physical parameters that control the rise time behaviour. In general, the models qualitatively reproduce aspects of the observed trends. We find that the brightness of the optical peak increases for larger progenitor radii and explosion energies, and decreases for larger masses. The dependence of the rise time on mass and explosion energy is smaller than the dependence on the progenitor radius. We find no evidence that the progenitors of SNe II-L have significantly smaller radii than those of SNe II-P.

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Section: A23 Physical Approximationssupporting

confidence: 53%

A comparative study of Type II-P and II-L supernova rise times as exemplified by the case of LSQ13cuw

Gáll

Polshaw

Kotak

et al. 2015

A&A

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“…1 and 2 agrees qualitatively with that of the effective expansion opacity in Fig. 1 of Karp et al (1977) if it is taken into account that we plot the flux instead of the opacity and prefer a logarithmic wavelength scale instead of a frequency scale.…”

Section: Single Infinitely Narrow Linessupporting

confidence: 79%

“…In particular Poisson distributed δ-lines have the advantage that many formulae can be integrated analytically and hence lead to relatively simple expressions for the expectation values of the radiative flux (whereas the more general expressions of Paper III frequently require involved numerical integrations); (iii) the connection between the concept of the expansion opacity by Karp et al (1977) and our more Send offprint requests to: R. Wehrse, e-mail: wehrse@ita.uni-heidelberg.de general comoving-frame formalism which for stochastically distributed lines is expressed in terms of an effective opacity.…”

Section: Introductionmentioning

confidence: 99%

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The diffusion of radiation in moving media

Wehrsě

Baschek

Waldenfels

2003

A&A

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Abstract. For a given velocity and temperature field in a differentially moving 3D medium, the vector of the radiative flux is derived in the diffusion approximation. Due to the dependence of the velocity gradient on the direction, the associated effective opacity in general is a tensor. In the limit of small velocity gradients analytical expression are obtained which allow us to discuss the cases when the direction of the flux vector deviates from that of the temperature gradient. Furthermore the radiative flux is calculated for infinitely sharp, Poisson distributed spectral lines resulting in simple expressions that provide basic insight into the effect of the motions. In particular, it is shown how incomplete line lists affect the radiative flux as a function of the velocity gradient. Finally, the connection between our formalism and the concept of the expansion opacity introduced by Karp et al. (1977) is discussed.

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“…In SNe Ia, a pseudo-continuum is formed by blending of a large number of lines which are mostly responsible for thermalization (Karp 1977). The wavelength dependence of the pseudocontinuum is one of the keys to understand the wavelength dependence of P. The ratio R between true absorption κ and total extinction, κ + σ Thomson , determines the thermalization optical depth, τ ≈ √ 3/R and, more important, the ratio between polarizing, i.e.…”

Section: Continuum Polarizationmentioning

confidence: 99%

VLT Spectropolarimetry of the Type Ia SN 2005ke

Patat¹,

Hoêflich²,

Baade³

et al. 2012

A&A

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Aims. In this study we try to answer the question whether or not subluminous Type Ia supernovae have additional distinctive properties when examined from the point of view of the explosion geometry. Methods. We have performed optical spectropolarimetric observations of the Type Ia SN 2005ke at 3 epochs (days −8, −7, and +76). The explosion properties are derived by comparing the data to explosion and radiation transfer models. Results. The supernova shows polarimetric properties that are very similar to the only other subluminous event for which spectropolarimetry is available, i.e. SN 1999by. The data present a very marked dominant axis, which is shared by both the continuum and lines such as Si ii λ6355, suggesting that the relatively large, global asymmetry is common to the photosphere and the line-forming region. The maximum polarization degree observed in the Si ii λ6355 absorption reaches 0.39 ± 0.08%. At variance with what is seen in core-normal Type Ia, SN 2005ke displays significant continuum polarization, which grows from the blue to the red and peaks at about 7000 Å, reaching ∼0.7%. The properties of the polarization and flux spectra can be understood within the framework of a subluminous delayed-detonation (DD), or pulsating DD scenario, or white dwarf (WD) mergers. The difference in appearance with respect to core-normal SNe Ia is caused by low photospheric temperatures in combination with layers of unburned C, and more massive layers of the products of explosive C and O burning. The comparatively high level of continuum polarization is explained in terms of a significant global asymmetry (∼15%), which is well reproduced by an oblate ellipsoidal geometry within the general context of a DD explosion. Conclusions. Our results suggest that SN 2005ke arose either from a single-degenerate system in which the WD is especially rapidly rotating, close to the break-up velocity, or from a double-degenerate merger. Based on the current polarization data, we cannot distinguish between these two possibilities. Possible tests are discussed.

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The opacity of expanding media - The effect of spectral lines

Cited by 160 publications

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A comparative study of Type II-P and II-L supernova rise times as exemplified by the case of LSQ13cuw

A comparative study of Type II-P and II-L supernova rise times as exemplified by the case of LSQ13cuw

The diffusion of radiation in moving media

VLT Spectropolarimetry of the Type Ia SN 2005ke

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