Age-Activity-Rotation Relationship in Solar-Type Stars Giancarlo Pace PHD student European Southern Observatory Universita’ di Trieste In collaboration with Luca Pasquini (supervisor at ESO)

Chr. Act. age & Star Formation Rate During late-type stars MS lifetime chromospheric activity and rotation decay Chr. Act. Chromospheric age observed for Field Stars age Ages + metallicities Chemical evolution & Star Formation Rate

Our Goal: Decaying Law New-Generation Telescopes Skumanich, 1972 Improved by Barry et al., 1987 Low resolution spectra New-Generation Telescopes Good data also for old and intermediate age Open Clusters

Indicator of Chromospheric Activity Emission core of the Ca II K line 1 A index Flux High resolution (R=60000), high S/N spectra UVES at Kueyen VLT HIRES at Keck v rot from Cross Correlation Profiles

Targets: 3 coeval pairs HYADES & PRAESEPE, 0.6 Gyr 15 and 7 stars respectively IC 4651 & NGC 3680, ~1.5 Gyr 5 and 2 stars M67 and the Sun, ~4.5 Gyr 7 stars in M67 Sun data from White and Livingston, 1981

Data Analysis Spectra normalization and rectification Subtraction of the IS absorption Index measurement Subtraction of the photospheric contribution Calibration in fluxes

age 0.6 Gyr 1.7 Gyr 4.5 Gyr Average spectra for each Cluster and for the Sun over the Solar-photosphere model 1.7 Gyr age 4.5 Gyr

IC 4651 + NGC 3680 = M67 + Sun Abrupt decay within ~1.5 Gyr Vertical bars = peak to peak spread IC 4651 + NGC 3680 = M67 + Sun Coeval pairs ~ same levels Abrupt decay within ~1.5 Gyr then no evolution NO POWER LAW

Abrupt decay after 0.6 Gyr Easy explanation of the Vaughan Preston gap

CONCLUSIONS High resolution, high S/N spectra of 36 stars in 5 open clusters were taken to study rotation and chromospheric activity. Abrupt decay before ~1.5 Gyr Natural explanation of the Vaughan Preston gap Later on the activity remains constant The rotational velocity has a similar trend Chromospheric ages can be reliable up to ~1.5 Gyr

Chromospheric Activity of 46 field stars 34 inactive, 4 intermediate, 8 active stars Active <t1 , t2<intermediate<t2,inactive>t2