August 11-15, 2014

Abstract

The very fast evolution of the VLTP object V4334 Sgr

Peter van Hoof (Royal Observatory of Belgium)

S. Kimeswenger (Universidad Catolica del Norte), A.A. Zijlstra (University of Manchester), M. Hajduk (Nicolaus Copernicus Astronomical Center), F. Herwig (University of Victoria), L. Decin (Catholic University of Leuven), M.A.T. Groenewegen (Royal Observatory of Belgium), L. Guzman-Ramirez (ESO-ALMA), S.. Ottl (University of Innsbruck), M. Pignatari (University of Basel), G.C. Van de Steene (Royal Observatory of Belgium)

It is well known that intermediate mass stars experience thermal pulses at the tip of the AGB. It is theorized that about 20% of all objects will experience one additional (very) late thermal pulse (VLTP) after they have left the AGB and have become the central star of a planetary nebula. Despite this high percentage, this process is only very rarely observed. The discovery of Sakurai's star (V4334 Sgr) in 1996 provided the first opportunity in modern times to observe a very late thermal pulse. This object has baffled the scientific community with its very fast evolution. To reproduce this evolution we have proposed a new theoretical model which suppresses convective mixing under the influence of flash burning after the ingestion of the remaining hydrogen envelope. A strong prediction of this model is that the star will evolve back to a temperature of 80,000K within a very short time. In an international collaboration we are monitoring this evolution using optical spectra (from the VLT) as well as radio observations (from the VLA and Merlin) to look for signs of ionization due to the reheating of the central star. In my talk I will give an overview of the recent results of this campaign. I will also briefly discuss our ALMA proposal that has been accepted for cycle 2 in which we aim to determine the isotope ratios of CNO which should help us determine the unique chemical signature produced by the hydrogen ingestion flash in this object.

Mode of presentation: oral