| 1. |
- Chugai, N. N., et al.
(författare)
-
Circumstellar interaction of the type Ia supernova 2002ic
- 2004
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 355, s. 627-637
-
Tidskriftsartikel (refereegranskat)abstract
- We propose a model to account for the bolometric light curve, the quasi-continuum and the CaII emission features of the peculiar type Ia supernova (SN) 2002ic, which exploded in a dense circumstellar envelope. The model suggests that the SN Ia had the maximum possible kinetic energy and that the ejecta expand in an approximately spherically symmetric (possibly clumpy) circumstellar environment. The CaII and the quasi-continuum are emitted by shocked SN ejecta that underwent deformation and fragmentation in the intershock layer. Modelling of the CaII triplet implies that the contribution of the OI 8446-Åline is about 25 per cent of the 8500-Åfeature on day 234, which permits us to recover the flux in the CaII 8579-Åtriplet from the flux of 8500-Åblend reported by Deng et al. We use the CaII doublet and triplet fluxes on day 234 to derive the electron temperature (~ 4400 K) in the CaII line-emitting zone and the ratio of the total area of dense fragments to the area of the shell, S/S0~ 102. We argue that CaII bands and the quasi-continuum originate from different zones of the shocked ejecta that reflect the abundance stratification of the supernova.
|
|
| 2. |
- Chugai, N. N., et al.
(författare)
-
Type II supernovae at high redshifts.
- 2000
-
Ingår i: Memorie della Società Astronomica Italiana. - 1824-016X. ; 71, s. 383-388
-
Tidskriftsartikel (refereegranskat)abstract
- A hydro code coupled with radiation transfer was applied to produce monochromatic light curves of two models of type II supernovae (SN II) simulating SN II-P and SN IIb (SN 1993J-like). The authors then used these template light curves to evaluate the possibility of detecting SNe II at different redshifts. With a 5 hour exposure at VLT/FORS the SN II-P model may be detected at z = 1. However, since the model of SN II-P is underluminous at early phase (t < 10 days) by ≍1.5 mag a detection at z = 2 is quiet plausible. SN IIb can be detected as far as at z = 4. For 100% detection efficiency up to z = 2 one expects to find roughly 1 SN II yr-1arcmin-2.
|
|
| 3. |
- Pozzo, M., et al.
(författare)
-
On the source of the late-time infrared luminosity of SN 1998S and other Type II supernovae
- 2004
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 352, s. 457-477
-
Tidskriftsartikel (refereegranskat)abstract
- We present late-time near-infrared (NIR) and optical observations of the Type IIn SN 1998S. The NIR photometry spans 333-1242 d after explosion, while the NIR and optical spectra cover 333-1191 and 305-1093 d, respectively. The NIR photometry extends to the M' band (4.7 μm), making SN 1998S only the second ever supernova for which such a long IR wavelength has been detected. The shape and evolution of the Hα and HeI 1.083-μm line profiles indicate a powerful interaction with a progenitor wind, as well as providing evidence of dust condensation within the ejecta. The latest optical spectrum suggests that the wind had been flowing for at least 430 yr. The intensity and rise of the HK continuum towards longer wavelengths together with the relatively bright L' and M' magnitudes show that the NIR emission was due to hot dust newly formed in the ejecta and/or pre-existing dust in the progenitor circumstellar medium (CSM). The NIR spectral energy distribution (SED) at about 1 yr is well described by a single-temperature blackbody spectrum at about 1200 K. The temperature declines over subsequent epochs. After ~2 yr, the blackbody matches are less successful, probably indicating an increasing range of temperatures in the emission regions. Fits to the SEDs achieved with blackbodies weighted with λ-1 or λ-2 emissivity are almost always less successful. Possible origins for the NIR emission are considered. Significant radioactive heating of ejecta dust is ruled out, as is shock/X-ray-precursor heating of CSM dust. More plausible sources are (a) an IR echo from CSM dust driven by the ultraviolet/optical peak luminosity, and (b) emission from newly-condensed dust which formed within a cool, dense shell produced by the ejecta shock/CSM interaction. We argue that the evidence favours the condensing dust hypothesis, although an IR echo is not ruled out. Within the condensing-dust scenario, the IR luminosity indicates the presence of at least 10-3 Msolar of dust in the ejecta, and probably considerably more. Finally, we show that the late-time (K-L')0 evolution of Type II supernovae may provide a useful tool for determining the presence or absence of a massive CSM around their progenitor stars.
|
|
| 4. |
- Chugai, Nikolai N., et al.
(författare)
-
The Type IIn supernova 1994W : evidence for the explosive ejection of a circumstellar envelope
- 2004
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 352, s. 1213-1231
-
Tidskriftsartikel (refereegranskat)abstract
- We present and analyse spectra of the Type IIn supernova (SN) 1994W obtained between 18 and 203d after explosion. During the luminous phase (first 100d) the line profiles are composed of three major components: (i) narrow P-Cygni lines with the absorption minima at -700kms-1 (ii) broad emission lines with blue velocity at zero intensity ~4000km s-1 and (iii) broad, smooth wings extending out to at least ~5000kms-1, most apparent in Hα. These components are identified with an expanding circumstellar (CS) envelope, shocked cool gas in the forward post-shock region, and multiple Thomson scattering in the CS envelope, respectively. The absence of broad P-Cygni lines from the SN is the result of the formation of an optically thick, cool, dense shell at the interface of the ejecta and the CS envelope. Models of the SN deceleration and Thomson scattering wings are used to recover the density (n~ 109cm-3), radial extent [~(4-5) × 1015cm] and Thomson optical depth (τT>~ 2.5) of the CS envelope during the first month. The plateau-like SN light curve is reproduced by a hydrodynamical model and is found to be powered by a combination of internal energy leakage after the explosion of an extended pre-SN (~1015cm) and subsequent luminosity from CS interaction. The pre-explosion kinematics of the CS envelope is recovered, and is close to homologous expansion with outer velocity ~1100kms-1 and a kinematic age of ~1.5yr. The high mass (~0.4Msolar) and kinetic energy (~2 × 1048erg) of the CS envelope, combined with low age, strongly suggest that the CS envelope was explosively ejected ~1.5yr prior to the SN explosion.
|
|
