An extensive set of optical and NIR photometry and low-resolution spectra the Type Ia supernova (SN Ia) 2003du was obtained using a number of facilities. The observations started 13 days before ...B-band maximum light and continued for 480 days with exceptionally good time sampling. The optical photometry was calibrated through the S-correction technique. The UBVRIJHK light curves and the color indices of SN 2003du closely resemble those of normal SNe Ia. SN 2003du reached a B-band maximum of 13.49 (+/-0.02) mag on JD2452766.38 (+/-0.5). We derive a B-band stretch parameter of 0.988 (+/-0.003), which corresponds to dM15=1.02 (+/-0.05), indicative of a SN Ia of standard luminosity. The reddening in the host galaxy was estimated by three methods, and was consistently found to be negligible. We estimate a distance modulus of 32.79 (+/-0.15) mag to the host galaxy, UGC 9391. The peak UVOIR bolometric luminosity of 1.35(+/-0.20) 10^43 erg/s and Arnett's rule implies that M(Ni56)=0.68 (+/-0.14)M_sun of Ni56 was synthesized during the explosion. Modeling of the UVOIR bolometric light curve also indicates M(Ni56) in the range 0.6-0.8 M_sun. The spectral evolution of SN 2003du at both optical and NIR wavelengths also closely resembles normal SNe Ia. In particular, the Si II ratio at maximum R(Si II)=0.22 (+/-0.02) and the time evolution of the blueshift velocities of the absorption line minima are typical. The pre-maximum spectra of SN 2003du showed conspicuous high-velocity features in the Ca II H&K doublet and infrared triplet, and possibly in Si II 6355, lines. We compare the time evolution of the profiles of these lines with other well-observed SNe Ia and we suggest that the peculiar pre-maximum evolution of Si II 6355 line in many SNe Ia is due to the presence of two blended absorption components.
First results of numerical simulations are presented which compute the dynamical evolution of a neutron star with a mass slightly below the minimum stable mass by means of a new implicit (general ...relativistic) hydrodynamic code. We show that such a star first undergoes a phase of quasi-static expansion, caused by slow nuclear \(\beta\)-decays, lasting for about 20 seconds, but then explodes violently. The kinetic energy of the explosion is around \(10^{49} erg\), the peak luminosity in electron anti-neutrinos is of order \(10^{52} erg/s\), and the thermodynamic conditions of the expanding matter are favorable for r-process nucleosynthesis. These results are obtained for the Harrison-Wheeler equation of state and a simple and, possibly, unrealistic treatment of \(\beta\)-decay rates and nuclear fission, which were adopted for comparison with previous works. However, we do not expect that the outcome will change qualitatively if more recent nuclear input physics used. Although our study does not rely on a specific scenario ofhow a neutron star starting from a bigger (and stable) masscan reach the dynamical phase, we assume that the final mass-loss event happens on a very short time scale, i.e., on a time scale shorter than a sound-crossing time, by removing a certain amount of mass as an initial perturbation. This assumption implies that the star has no time to adjust its nuclear composition to the new mass mass through a sequence of quasi-equilibria. In the latter case, however, there exists no stable configuration below the minimum mass, because the equation of state of fully catalyzed matter is too soft. Therefore, the dynamics of the explosion will not be too different from what have obtained if different initial perturbations are assumed.
Mon.Not.Roy.Astron.Soc.348:261,2004 We present optical/near-infrared photometry and spectra of the type Ia SN
2002bo spanning epochs from -13 days before maximum B-band light to +102 days
after. The ...pre-maximum optical coverage is particularly complete. In some
respects, SN 2002bo behaves as a typical "Branch normal" type Ia supernova (SN
Ia) at optical and IR wavelengths. We find a B-band risetime of 17.9+-0.5 days,
a Dm_{15}(B) of 1.13+-0.05, and a M_B=-19.41+-0.42. However, comparison with
other type Ia supernovae having similar Delta m_{15}(B) values indicates that
in other respects SN 2002bo is unusual. While the optical spectra of SN 2002bo
are very similar to those of SN 1984A, lower velocities and a generally more
structured appearance are found in SNe 1990N, 1994D and 1998bu. For supernovae
having Dm_(15)(B) > 1.2, we confirm the variation of R(SiII) (Nugent et al.
1995) with Dm_(15)(B). However, for supernovae such as SN2002bo, with lower
values of Dm_(15)(B) the relation breaks down. Moreover, the evolution of
R(SiII) for SN 2002bo is strikingly different from that shown by other type Ia
supernovae. The velocities of SN 2002bo and 1984A derived from SII 5640A, SiII
6355A and CaII H&K lines are either much higher and/or evolve differently from
those seen in other normal SNe Ia events. We suggest that the unusually low
temperature, the presence of high-velocity intermediate-mass elements and the
low abundance of carbon at early times indicates that burning to Si penetrated
to much higher layers than in more normal type Ia supernovae. This may be
indicative of a delayed-detonation explosion.
A series of two dimensional numerical simulations of explosive nuclear burning is presented for white dwarfs near the Chandraskhar mass. We assume that the burning begins as a slow deflagration front ...at or near the center of the star, and continues until the density in the burning regions has declined to about 10\(^7\) g cm\(^{-3}\), where the flame is essentially extinguished. We employ a novel numerical representation of the turbulent flame brush based upon ideas previously developed for modelling laboratory combustion and explore in some detail the sensitivity of the outcome to the manner in which burning is initiated. In particular, we simulate 1) a centrally ignited deflagration, 2) off-center ignition at a single ``point", and 3) simultaneous off-center ignition at five ``points". We find that the amount of \(^{56}\)Ni that is produced and other observable properties depend sensitively upon how the fuel is ignited.
Astrophys.J.623:L37-L40,2005 Evidence of high-velocity features such as those seen in the near-maximum
spectra of some Type Ia Supernovae (eg SN 2000cx) has been searched for in the
available SNIa ...spectra observed earlier than one week before B maximum. Recent
observational efforts have doubled the number of SNeIa with very early spectra.
Remarkably, all SNeIa with early data (7 in our RTN sample and 10 from other
programmes) show signs of such features, to a greater or lesser degree, in CaII
IR, and some also in SiII 6255A line. High-velocity features may be interpreted
as abundance or density enhancements. Abundance enhancements would imply an
outer region dominated by Si and Ca. Density enhancements may result from the
sweeping up of circumstellar material by the highest velocity SN ejecta. In
this scenario, the high incidence of HVFs suggests that a thick disc and/or a
high-density companion wind surrounds the exploding white dwarf, as may be the
case in Single Degenerate systems. Large-scale angular fluctuations in the
radial density and abundance distribution may also be responsible: this could
originate in the explosion, and would suggest a deflagration as the more likely
explosion mechanism. CSM-interaction and surface fluctuations may coexist,
possibly leaving different signatures on the spectrum. In some SNe the HVFs are
narrowly confined in velocity, suggesting the ejection of blobs of burned
material.
The ESC-RTN optical spectroscopy data-set for SN 2005cf is presented and analyzed. The observations range from -11.6 and +77.3 days with respect to B-band maximum light. The evolution of the spectral ...energy distribution of SN 2005cf is characterized by the presence of high velocity SiII and CaII features. SYNOW synthetic spectra are used to investigate the ejecta geometry of silicon. Based on the synthetic spectra the SiII high velocity feature appears detached at 19500 km/s. We also securely establish the presence of such feature in SN 1990N, SN 1994D, SN 2002er and SN 2003du. On a morphological study both the CaII IR Triplet and H&K absorption lines of SN 2005cf show high velocity features centered around 24000 km/s. When compared with other Type Ia SNe based on the scheme presented in Benetti et al. 2005 SN 2005cf definitely belongs to the LVG group.
Extensive light and colour curves for the Type Ia supernova SN 2002er are
presented as part of the European Supernova Collaboration. We have collected
UBVRI photometry from ten different telescopes ...covering the phases from 7 days
before until 619 days after maximum light. Corrections for the different
instrumental systems and the non-thermal spectrum of the supernova
(S-corrections) have been applied. With the densely sampled light curves we can
make detailed comparisons to other well-observed objects. SN 2002er most
closely resembles SN 1996X after maximum, but clearly shows a different colour
evolution before peak light and a stronger shoulder in V and R bands compared
to other well-observed SNe Ia. In particular, the rise time appears to be
longer than what is expected from rise-time vs.decline-rate relation. We use
several methods to determine the reddening towards SN 2002er based on the
colour evolution at near peak and at late phases. The uvoir (bolometric) light
curve shows great similarity with SN 1996X, but also indications of a higher
luminosity, longer rise time and a more pronounced shoulder 25 days past
maximum. The interpretation of the light curves was done with two independent
light curve codes. Both find that given the luminosity of SN 2002er the 56Ni
mass exceeds 0.6 Msun with prefered values near 0.7 Msun. Uncertainties in the
exact distance to SN 2002er are the most serious limitation of this
measurement. The light curve modelling also indicates a high level of mixing of
the nickel in the explosion of SN 2002er.
Shell effects in nuclei close to the neutron-drip lines have been investigated. It has been demonstrated in the relativistic mean-field theory that nuclei very far from stability manifest the shell ...effects strongly. This behaviour is in accord with the predictions of nuclear masses in the finite-range droplet model including shell corrections. As a consequence we find a large neutron halo in nuclei near the neutron-drip line. The shell effects predicted in the existing Skyrme mean-field theory in comparison are significantly weaker than those of the other approaches.
We present optical and near-infrared photometry and spectroscopy of the Type Ia SN 2003cg, which exploded in the nearby galaxy NGC 3169. The observations cover a period between -8.5 and +414 days ...post-maximum. SN 2003cg is a normal but highly-reddened Type Ia event. Its B magnitude at maximum B_max = 15.94+/-0.04 and Delta m_15(B)_obs = 1.12+/-0.04 (Delta m_15(B)_intrinsic = 1.25+/-0.05). Allowing R_v to become a free parameter within the Cardelli et al. (1989) extinction law, simultaneous matches to a range of colour curves of normal SNe Ia yielded E(B-V) = 1.33+/-0.11, and R_v = 1.80+/-0.19. While the value obtained for R_v is small, such values have been invoked in the past, and may imply a grain size which is small compared with the average value for the local ISM.
We present a statistical model which shows the influence of turbulence on a thermonuclear flame propagating in C+O white dwarf matter. Based on a Monte Carlo description of turbulence, it provides a ...method for investigating the physics in the so-called distributed burning regime. Using this method we perform numerical simulations of turbulent flames and show that in this particular regime the flamelet model for the turbulent flame velocity loses its validity. In fact, at high turbulent intensities burning in the distributed regime can lead to a deceleration of the turbulent flame and thus induces a competing process to turbulent effects that cause a higher flame speed. It is also shown that in dense C+O matter turbulent heat transport is described adequately by the Peclet number, Pe, rather than by the Reynolds number, which means that flame propagation is decoupled from small-scale turbulence. Finally, at the onset of our results we argue that the available turbulent energy in an exploding C+O white dwarf is probably too low in order to make a deflagration to detonation transition possible.
