1) Ulrich Nöbauer will talk about:
"Type Ia supernovae within dense carbon-oxygen rich envelopes: a model
for 'Super-Chandrasekhar' explosions?"
We investigate the consequences of fairly normal Type Ia supernovae
being embedded in compact and dense envelopes of carbon and oxygen
rich circumstellar material by means of detailed radiation
hydrodynamic simulations. Our main focus rests on exploring the
effects of the interaction between ejecta and circumstellar material
on the ejecta evolution and the broad-band light curve. In our
calculations, we find that a strong reverse shock efficiently
decelerates and compresses the ejecta material. This leads to a
significant broadening of the optical light curve, a longer rise to
maximum and a slower decline in the tail phase. During the
interaction, substantial radiative energy is generated, which mostly
emerges in the extreme ultraviolet and X-ray regime. Only if
reprocessing due to radiation--matter interactions is very efficient,
a significant boost in the optical light curve is observed. We discuss
these findings in particular in the context of the super-luminous
event SN 2009dc. As our calculations are able to reproduce a number of
its peculiar properties, we conclude that the flavour of the
interaction scenario investigated in this work constitutes a promising
candidate to explain such 'Super-Chandrasekhar' supernovae.
2) Suhail Dhawan will present:
"Near Infrared and bolometric properties of fast-declining SN Ia
indicate sub-Chandra progenitors"
Dedicated searches for Type Ia supernovae (SN~Ia) have discovered
several classes exhibiting photometric and spectroscopic
peculiarities. In this study, we characterise the diversity in the
near infrared (NIR) and bolometric properties of the class of SN~Ia
with fast optical decline rates ($\Delta m_{15}$ \textgreater 1.6) and
compare them to normal ($\Delta m_{15}$ $\leq$ 1.6) SN~Ia.
Fast-declining show a large range of peak bolometric luminosities
($L_{max}$ differing by upto a factor of $\sim$ 8). The SNe appear to
be split into two groups based on their $L_{max}$. All fast-declining
SN~Ia with $L_{max}$ \textless 0.3$10^{43}ergs^{-1}$ are
spectroscopically classified as 91bg-like and show only a single NIR
peak. SNe with $L_{max}$ \textgreater 0.5 $10^{43}ergs^{-1}$ appear to
smoothly connect to normal SN~Ia. The total ejecta mass ($M_{ej}$)
values for SNe with enough late time data are $\lesssim$ 1
$M_{\odot}$, indicating a sub-Chandrasekhar mass progenitor for these
SNe.
