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Séminaire du Jeudi 11 février 2016

The evolution of surface magnetic fields in young solar-type stars

Colin Folsom (IPAG)
Thursday February 11th - 11am
IPAG Seminar Room - IPAG

The surface rotation rates of young solar-type stars vary rapidly with age from the end of the pre-main sequence through the early main sequence. Important changes in the dynamos operating in these stars may result from this evolution, which should be observable in their surface magnetic fields. Here we present a study aimed at observing the evolution of these magnetic fields through this critical time period. We observed stars in open clusters and stellar associations of known ages, and used Zeeman Doppler Imaging to characterize their complex large-scale magnetic fields. Presented here are results for a sample of stars, from 7 associations, with ages from 20 to 625 Myr, masses from 0.7 to 1.2 times the sun, and rotation periods from 0.4 to 11 days. We find complex large-scale magnetic field geometries, with global average strengths from 10 to 140 G. There is a clear trend towards decreasing average large-scale magnetic field strength with age, and a tight correlation ! between magnetic field strength and Rossby number. Comparing the magnetic properties of our zero-age main sequence sample to those of both younger and older stars, it appears that the magnetic evolution of solar-type stars during the pre-main sequence is primarily driven by structural changes, while it closely follows the stars’ rotational evolution on the main sequence.

PDF - 5.2 Mo

Sous la tutelle de:

tutelles

Sous la tutelle de:

CNRS Université Grenoble Alpes