Supernova Atmosphere Research Articles

Ionization by high-energy particles and the electron scattering opacity in supernovae

Ionization equilibrium equations appropriate for supernova atmospheres are described. The solution of these equations indicate the high-energy particles associated with radioactive Ni-56 and Co-56 decay sustain a significant degree of ionization in the supernova plasma. Under certain physical conditions, the resulting electron scattering opacity can be many orders of magnitude greater than LTE estimates predict. A straightforward application of the present results to standard (diffusion approximation) hydrodynamic computations is proposed in which the non-LTE electron scattering opacity is expressed in terms of the local radioactive decay energy deposition rate and the mass density. Application to an analytic supernova dynamic evolution computation is presented to illustrate the results expected from more detailed calculations. 50 refs.

SN 1987A: Ultraviolet Observations and Mass Loss

AbstractMass loss from the B3 Ia progenitor star for SN 1987A is revealed by the recent emergence of narrow ultraviolet emission lines. The emitting gas is nitrogen-rich, has low velocity, and may be located a light-year from the supernova. This gives every sign of having been ejected from the SK −69 202 progenitor when it was a red supergiant, prior to its brief and ultimately violent life as a blue supergiant. Changes in the hydrogen line profiles during the early evolution provide a way to estimate the density distribution in the supernova atmosphere, and the mass of hydrogen it contains. A preliminary estimate is that the power-law index of density in the envelope goes as V−11 and the mass that lies above a velocity of 6, 000 km s−1 is between 1 and 6 solar masses.

A Simple Treatment of the Problem of Radiative Transfer in Supernova-Like Envelopes

Since the only direct information, on the physics of supernova explosions comes from spectrophotometry of their light curves, it is wortwhile to put considerable effort on understanding the properties of supernova atmospheres. Two problems appear, however, in doing so. First, the mean free path of a photon in the region where the Spectrum forms (the atmosphere) is an important fraction of the supernova size and the plane parallel approximation breaks down. Second, the roles of scattering and absorption in the formation of the continuum are not clearly determined.The complications introduced by spherical geometry arise from the angular derivative terms in the transfer equation and from the high degree of anisotropy introduced by the geometry. The complications introduced by scattering arise from the presence of the mean intensity in the source term of the transfer equation. As an outcome, its numerical solution is time consuming, and classical simplifications are not possible due to the strong anisotropy of the radiation field. In hydrodynamical calculations it is better to calculate the moments of the radiation field, but the success of this method depends on the possibility of replacing the infinite set of differential equations by the equations of low order moments plus a closure relationship that keeps all the properties of the higher moments.

Ultraviolet observations of SN 1987A

UV observations of the supernova in the LMC, SN 1987A, were carried out with the IUE satellite. The earliest data show that the UV flux from the supernova was already declining while the optical flux was still rising. The UV spectrum at these epochs consists of broad features associated with the supernova atmosphere punctuated by sharp interstellar absorptions. The rapid decline of the supernova in the short-wavelength ultraviolet allows a glimpse of the stars which remain. One of these is star 2, a neighbor of Sanduleak -69 deg 202, while the other appears to be star 3, a fainter close neighbor of the Sanduleak star. If this is correct, then the star which exploded is Sanduleak -69 deg 202.

The early spectral phase of type Ib supernovae - Evidence for helium

A near-infrared spectrum and several optical spectra of SN 1983N obtained over a period from 10 days before maximum light to about a week after maximum and of SN 1984L from about maximum light to about 60 days later are presented. On the basis of these spectra it is argued that the first definite identification of helium in supernova ejecta near maximum light has been made. The emergence of oxygen emission lines which presage the dramatic transition to the supernebular phase is identified. Supernova atmosphere models which are consistent with the observations are presented, and it is argued that a strong departure of helium level populations from LTE is necessary. The current status of SNe Ib, the arguments that they result from core collapse in moderately massive stars, and some of the immediate work necessary to further clarify the nature of these events are summarized.

SUPERNOVAE, SUPERNEBULAE, AND NUCLEOSYNTHESIS.

ABSTRACT Supernova atmosphere calculations continue to show that variants of previously calculated carbon-deflagration models provide a good representation of the maximum light spectra of classical type Ia supernovae including the ultraviolet deficit. Careful consideration of the conditions leading to central thermonuclear runaway of degenerate carbon shows that runaway can, however, lead to detonation and direct conflict with observations. As witnessed by the spectra of type Ib supernovae, massive stars are expected to be the primary source of oxygen. Estimates of the absolute production of oxygen in massive stars suggest that if all stars more massive than ≡12 Msun; explode as supernovae, oxygen would be overproduced in the solar neighborhood, an effect exacerbated by the recent increase in the reaction rate for 12C(α, γ)16O.

Supernova colors and systematic flux dilution

view Abstract Citations (2) References (16) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Supernova Colors and Systematic Flux Dilution Fu, A. J. ; Arnett, W. D. Abstract A straightforward investigation of the UBVRK colors of the type I supernova SN 1972e in NGC 5253 and SN 1981b in NGC 4536 over the period of about 20-50 days after maximum light provides strong evidence for significant, wavelength-dependent, continuum flux dilution. Over the times considered in the evolution of the event, the continuum spectrum is essentially a blackbody at infrared wavelengths and a diluted blackbody at visible and ultraviolet wavelengths, the dilution increasing with increasing photon energy. A quantitative attempt to describe this dilution, using only a monochromatic dilution factor due to electron scattering in the supernova atmosphere, suggests that other effects are probably present and may be dominant. A major consequence of the above picture is that type I supernovae are substantially dimmer, therefore closer in distance, than their infrared color temperature would indicate, and substantially brighter, therefore much further away, than the UBV color temperature would indicate. Publication: The Astrophysical Journal Pub Date: August 1986 DOI: 10.1086/164458 Bibcode: 1986ApJ...307..726F Keywords: Flux Quantization; Stellar Color; Stellar Spectrophotometry; Supernovae; Black Body Radiation; Dilution; Radiative Transfer; Radii; Stellar Temperature; Astrophysics; SPECTROPHOTOMETRY; STARS: SUPERNOVAE full text sources ADS | data products SIMBAD (1) NED (1)

A dynamical model of type I supernova atmosphere with the velocity gradient

A compact structure of a low-mass Type I presupernovae is assumed to be an essential feature of the hydrodynamical problem dealing with the supernova Type I (SNI) envelope outbursts. This structure is characterized by a degenerate carbon-oxygen core, which suffers a thermonuclear explosion of carbon fuel (M 0≃1.40M ⊙), and by a compact lowmass envelope (M e ≲0.1M ⊙) with external radiusR e≃109 cm. The parameters, of this hydrostatic envelope are specified and then, for a relatively small explosion energy, ofW 0≃(2–10)×1049 erg, hydrodynamic problem of the envelope ejection is solved numerically. This energy comes from neutrino-induced detonative carbon burning. The resulting structure of the SNI atmosphere expanding with the velocity gradient can be employed for an interpretation of the observed SNI spectra. In accordance with our previous papers, the SNI light curves are considered to occur due to an additional slow (with time-scale 106–107 s) release of the bulk of the SNI energy,W≃1051, erg. The slow energy release does not, however, affect the structure of the outermost expanding layers of the envelope which are responsible for the SNI spectra.

The type II supernova 1979c in M100 and the distance to the Virgo cluster

Optical spectra of supernova 1979c in M100 obtained between 1979 April 22 and 1979 November 24 are presented and discussed in detail. Interstellar lines originating from both our Galaxy and M100 are examined. Synthetic spectra computed using a blackbody photosphere and a pure scattering expanding atmosphere successfully model the continua and P Cygni profiles of the supernova spectra up to May 28. The H..cap alpha.. profile is not explained by pure resonance scattering, but collisional excitation may be responsible for the net emission in this line as well as the Mg II lambda2798 emission seen in IUE spectra. Velocities and temperatures derived from the spectra are combined with photometric data to determine the distance to the supernova by the Baade method. We find the distance to be 23 +- 3 (rms) Mpc, corresponding to a Hubble parameter of about 60 km s/sup -1/ Mpc/sup -1/. The precursor star seems to have had an extended circumstellar envelope, and the mass of the precursor is estimated to have been at least 9 M/sub sun/. The chemical composition of the supernova atmosphere is discussed both from the standpoint of H II region observations and the synthetic spectra.