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