[Astronomy seminar] Astronomy seminar Friday 15/3 10:30 FC61: Richard I. Anderson

[Astronomy seminar announcements]

(Apart from the seminar in the morning, Rubén Asensio Torres will defend 
his thesis in the afternoon.)

Astronomy seminar
============

Time & location: Friday 15/3, 10:30 in FC61

Speaker: Richard I. Anderson (ESO)

Title:
New Light on Standard Candles: Cepheids as sensitive stellar 
laboratories and accurate cosmic yardsticks

Abstract:
This talk presents the crucial role that type-I Cepheid variable stars 
play in improving the understanding of how stars and the cosmos evolve. 
Starting from the recently reported Hubble constant tension that may 
imply a need for new physics beyond standard cosmology, I will describe 
ongoing efforts to measure H0 with an accuracy of 1%. Specifically, I 
will present an ongoing large observing program operating on both 
hemispheres that has measured more than 15,000 high-precision radial 
velocities of Cepheids in support of accurate parallaxes and alternative 
distance estimates based on Baade-Wesselink-type methods. Highlighting 
the impact of binaries for accurate parallax determination, I will show 
that stars physically associated with Cepheids contribute a modest 
photometric bias of less than 0.23% to H0, which may be further reduced 
in the future. The second part of the talk presents how rotation is 
expected to impact the evolutionary paths of Cepheids and how this 
relates to their use as cosmic yardsticks. Time permitting, I will 
present the curious case of Polaris, our nearest Cepheid, whose 
Gaia-based luminosity estimate and multi-periodic variability seem to 
defy theory, thus underlining the urgent need for a more detailed 
astrophysical understanding of our most important standard candles.

Arjan Bik will serve as a host for the speaker.

Other Friday activities in March:

15/3 (Fri) @ 13:00 : PhD defence Ruben Asensio Torres (SU)
22/3 (Fri) : Open slot, NO SEMINAR scheduled (yet)
29/3 (Fri) @ 10:30 : Emilia Kilpua (Helsinki)

All welcome!
       Alexis Brandeker (Astronomy seminar organiser VT 2019)