[Astronomy seminar] Reminder: Astronomy seminar Today at 10:30 FC61: Richard I. Anderson

[Astronomy seminar announcements]

Hi everyone,
welcome to today seminar. Richard will talk about stellar variability, tension in the measurement of the Hubble constant, and use GAIA measurement to better understand these stellar standard candles.

Angela


On 11 Mar 2019, at 11:38, Alexis Brandeker <alexis at astro.su.se<mailto:alexis at astro.su.se>> wrote:

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

Astronomy seminar
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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)



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Angela Adamo

Assistant professor
Department of Astronomy,
Stockholm University and Oskar Klein Centre
SE-10691 Stockholm - Sweden
tel: +46 (0)8 5537 8556
email: angela.adamo at astro.su.se<mailto:angela.adamo at astro.su.se>
http://ttt.astro.su.se/~adamo
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