Scientific case and motivation

Type Ia supernovae are bright stellar explosions, observed in old as well as young stellar

populations and are believed to be thermonuclear explosions of degenerate carbon-oxygen white

dwarfs, most likely triggered by the compression of the objects as they grow in mass towards the

Chandrasekhar limit. They are one of the main sites of nucleosynthesis in the Universe, being

responsible for most of the iron ever produced. Their tight peak luminosity – light curve shape

relation has enabled their use as distance indicators in cosmology, giving the first clues that the

expansion of the Universe is accelerating. Yet, the the configuration and trigger of the explosions

are unknown. Three years ago we had a very successful Lorentz center workshop on this topic and

the current one was to see where we stand now. There have been many new developments, both on

the observational as well as the theoretical side. In this Lorentz workshop we again brought together

a significant fraction of the researchers working on the different observable signatures of the



The workshop

A total of 55 participants from 9 countries participated in this second workshop in a series. Given

the fast developments in the field, the mornings were filled with short talks in which almost all

participants updated each other on the newest results. These include the non-detection of any signs

of progenitors, companions, interaction with progenitor winds etc. The 2011fe supernova in M101

provides particularly strong constraints. The progenitor models have been developed much further,

showing that there are many possibilities that still have to be explored further in order to interpret

them in the light of the observational signatures. The afternoons were structured around either

“round table” discussions, or moderated discussions. In these discussions the participants had the

opportunity to exchange ideas and sharpen their own future research plans. At several points in the

discussion participation of PhD students was stimulated (enforced) by allowing only them to talk.


Final remarks

The workshop was again a great success. Many participants were very excited about the topics, the

mix of participants and the set-up of the workshop and expressed the hope that there would be a

third one in the series in a few years time. The success was certainly also due to the excellent

facilities and support of the Lorentz center. We also gratefully acknowledge funding from the

Lorentz Center, NOVA and NWO.