Seminars and Colloquia at ESO Garching and on the campus

Asteroseismology uses the natural oscillation modes of stars to study their interiors. The wonderfully precise measurements

by NASA's Kepler and TESS missions are ideal data sources for the technique. These space telescopes have been monitoring

the brightness of hundreds of thousands of stars, with the main goal of discovering extra-solar planets as they transit their parent

stars.  At the same time, observations of stellar oscillations have led to a revolution in asteroseismology. I will discuss some of the

key results, including the use of gravity modes to probe the cores of red giant stars, the characterization of stars found to host exoplanets,

and the measurement of ages for young stellar associations. I will also describe how the VLT is playing its part by detecting weak

oscillations in K dwarfs.

For nearly three decades, high-energy astrophysicists at the CfA have  been collaborating with statisticians around the world to develop

a wide range of astrostatistical methods. Our modus operandi is to pick out a pesky astronomical data analysis problem, and analyze it

rigorously  using modern statistical methods and make advances in both astronomical inference and statistical methods. I will illustrate this

method with  some recent examples, like using Hidden Markov Models to find persistent  quiescent coronal emission in active flaring stars,

discovering that  solar flare occurrences are not Poisson distributed (and consequences  thereof), and employing Minimum Descriptor Length

methods to find change points in space, time, and energy data cubes. I will also briefly touch  on ongoing projects that are dealing with issues

of pileup, fitting  power-laws, catalog cross-matching, deconvolution, and systematic errors.

White dwarf binaries are expected to be the most numerous sources in LISA. Models predict that about 10 000 sources will be

individually resolved and that millions of others will combine into an unresolved foreground.  The shape and amplitude of the background

as well as the orbital frequencies of the individual detections will be very informative on the evolution of low mass binary stars and also the

shape of the Milky Way. It was recently shown that extragalactic white dwarfs will also create a background. In thediscussion I will show what

we currently know about these signals and how their combined information can help us understand binary evolution.

Measuring the Hubble constant is difficult. In the local universe, the H0 determination is hampered by two impediments: the local disturbance of the expansion field and the rarity of luminous distance indicators with a reliable calibration. This led to the principle of the distance ladder, where distance indicators are calibrated at lower distances and then applied as calibrators of another distance indicator at larger distances. Several methods have been used in the past years to measure the local expansion rate, but they have not converged. In addition, some of the local H0 determinations disagree with the derived expansion rate from the Lambda CDM model as calibrated by the cosmic microwave background resulting in the ‘Hubble tension’. Recently, a Garching team has improved the Expanding Photosphere Method (EPM) for type II supernovae to derive H0 bypassing the distance ladder. This promises to become an independent and unique probe of the cosmic expansion rate.