SAC Seminar: Hans Kjeldsen on the SWIFT spacecraft and Rasmus Handberg on extraction of individual oscillation modes from the Kepler Red Giants data
Oplysninger om arrangementet
1. Hans Kjeldsen will talk 10 min about the SWIFT spacecraft with respect to the 1 million seconds of observing time open to the Danish community and the upcoming proposal deadline for the period 2014 July - 2015 June.
2. Rasmus Handberg will talk about extraction of individual oscillation modes from the Kepler Red Giants data.
In Kepler Red Giant stars, detailed peakbagging, meaning the extraction of individual oscillation modes and all their characteristics, have only been performed in a handful of stars. The discipline has proven itself extensively for main-sequence and sub-giant stars, but has not been applied to a large extent to evolved Red Giants. This has mainly been due to complications introduced by the many mixed dipole modes.
In this talk I will report on an extensive peakbagging effort on the evolved red giant stars of the open cluster NGC 6819. This consists of ~50 stars spanning all the way up the red giant branch (RGB) and down to and including the red clump (RC). These stars represent a unique sample, because of their common distance, metallicity, age and length of observation (Q0-Q17).
By employing sophisticated pre-processing of the time series and Markov Chain Monte Carlo (MCMC) techniques we have extracted individual frequencies, heights and linewidths for hundreds of oscillation modes in the sample of stars. For some of the stars, rotational splittings could also be obtained.
I will show that “average” asteroseismic parameters derived from these can be used to distinguish the stellar evolutionary state between RGB and RC stars, without having to measure the often difficult dipole modes. Furthermore, I will show how the fitting of some of these dipole modes can improve the detectability of acoustic glitches.