Age-Activity-Rotation Age-Activity-Rotation Relationship in Relationship in Solar-Type StarsSolar-Type StarsGiancarlo Pace PHD studentGiancarlo Pace PHD student

European Southern ObservatoryEuropean Southern Observatory

Universita’ di TriesteUniversita’ di Trieste

In collaboration with Luca Pasquini (supervisor at ESO)

observedobserved

Chromospheric ageChromospheric age

for Field Starsfor Field Stars

Ages + metallicities Ages + metallicities Chemical evolutionChemical evolution

&&

Star Formation RateStar Formation Rate

During late-type stars MS lifetime chromospheric activity and rotation decay

Our Goal:Our Goal: Decaying LawDecaying Law

New-Generation TelescopesNew-Generation Telescopes

Good data also for old and Good data also for old and intermediate age Open Clustersintermediate age Open Clusters

Skumanich, 1972 Improved by Barry et al., 1987

Low resolution spectra

Indicator of Indicator of Chromospheric ActivityChromospheric Activity

Emission core of the Ca II K lineEmission core of the Ca II K line

1 A index1 A index FluxFlux

High resolution (R=60000), High resolution (R=60000), high S/N spectrahigh S/N spectraUVES at Kueyen VLT UVES at Kueyen VLT HIRES at KeckHIRES at Keck

vv rot rotfrom Cross Correlation Profilesfrom Cross Correlation Profiles

Targets: 3 coeval pairsTargets: 3 coeval pairs

HYADES & PRAESEPE, 0.6 GyrHYADES & PRAESEPE, 0.6 Gyr

15 and 7 stars respectively15 and 7 stars respectively IC 4651 & NGC 3680, ~1.5 GyrIC 4651 & NGC 3680, ~1.5 Gyr

5 and 2 stars5 and 2 stars M67 and the Sun, ~4.5 GyrM67 and the Sun, ~4.5 Gyr

7 stars in M677 stars in M67

Sun data from Sun data from White and Livingston, 1981White and Livingston, 1981

Data AnalysisData Analysis

Spectra normalization and rectificationSpectra normalization and rectification Subtraction of the IS absorptionSubtraction of the IS absorption Index measurementIndex measurement Subtraction of the photospheric Subtraction of the photospheric

contributioncontribution Calibration in fluxesCalibration in fluxes

Average spectra for eachCluster and for the Sun over the Solar-photosphere model

age

ICIC 4651 + NGC 3680 4651 + NGC 3680

==M67 + SunM67 + Sun

Abrupt decay within ~1.5 Gyr then no evolution NO POWER LAW

Vertical bars = peak to peak spread

Coeval pairs ~ same levels

Easy explanation of the

Vaughan Preston gap

Abrupt decay after 0.6 Gyr

CONCLUSIONSCONCLUSIONS High resolution, high S/N spectra of 36 stars in High resolution, high S/N spectra of 36 stars in

5 open clusters were taken to study 5 open clusters were taken to study rotationrotation and and chromospheric activity.chromospheric activity.

Abrupt decay before ~1.5 Gyr Abrupt decay before ~1.5 Gyr Natural explanation of the Vaughan Preston Natural explanation of the Vaughan Preston

gapgap Later on the activity remains constantLater on the activity remains constant The rotational velocity has a similar trendThe rotational velocity has a similar trend Chromospheric ages can be reliable up to ~1.5 Chromospheric ages can be reliable up to ~1.5

GyrGyr

Chromospheric Activity of 46 field starsChromospheric Activity of 46 field stars

34 inactive, 4 intermediate, 8 active stars34 inactive, 4 intermediate, 8 active stars

Active <tActive <t1 , 1 , tt22<intermediate<t<intermediate<t22,inactive>t,inactive>t22