We have completed an important step towards our long-term goal of performing cosmological distance measurements with type IIP supernovae (SNe IIP). This work is lead by Christian Vogl who has significantly extended the capabilities of our Monte Carlo-based radiative transfer code TARDIS ¹. It is now capable of accurately performing spectral synthesis for hydrogen-dominated supernovae. As a first demonstration, we have calculated a new set of dilution factors, which can be used in the expanding photosphere method (EPM) to determine distances to SNe IIP. We compare our results with the two previously published sets of dilution factors, discuss possible origins for their discrepancies and, for the first time, investigate the influence of metallicity. Our findings are summarized in a paper, which has been accepted for publication in Astronomy & Astrophysics. A preprint version can be found on the arxiv.

We are happy to announce that we have just released a new major version of the open-source Monte Carlo radiative transfer code TARDIS. Compared to version 1, this is a major step forwards and includes many changes and improvements, particularly:

Continuing the collaboration with Alexandra Kozyreva, we have studied the very bright Type II supernova OGLE073-14, investigating a possible pair-instability mechanism. Starting from realistic stellar evolution models for pair-instability supernovae (PISN), we explored the influence of a number of properties such as the total mass of radioactive nickel produced, its distribution in the ejecta and the mixing of hydrogen and identified two possible PISN models for OGLE073-14. The bolometric and broad-band light curves we calculated for these models match the observations very well. In addition, our collaborator Markus Kormer produced details spectral predictions for the models which we also compared to the observations. Hereby, we were able to successfully reproduce important observed spectral features. Most importantly, our models do not seem to suffer from a strong flux suppression in the short wavelength range which has been previously predicted for PISN. From our findings we conclude that a PISN origin of OGLE073-14 is possible and that it is actually one of the most promising candidates for this mechanism. Our results are summarized in a paper which has just been accepted for publication in MNRAS. A preprint may be found on the arxiv.

Upcoming high-cadence transient survey programs will produce a wealth of observational data for Type Ia supernovae. These data sets will contain numerous events detected very early in their evolution, shortly after explosion. We have calculated synthetic light curves with the radiation hydrodynamical approach STELLA for a number of different explosion models, specifically focussing on these first few days after explosion. Our research has been published in Monthly Notices of the Royal Astronomical Society and is highlighted on the webpage of MPA.