AgeActivityRotation Relationship in SolarType Stars

1
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)
2
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
3
Our Goal
Decaying Law
Skumanich, 1972
Improved by Barry et al., 1987
Low resolution spectra
New-Generation Telescopes
Good data also for old and intermediate age
Open Clusters
4
Indicator of Chromospheric Activity
Emission core of the Ca II K line
1 A index
Flux
High resolution (R60000), high S/N spectra UVES
at Kueyen VLT HIRES at Keck
v rot from Cross Correlation
Profiles
5
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

6
Data Analysis

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

7
0.6 Gyr
Average spectra for each Cluster and for the Sun
over the Solar-photosphere model
1.7 Gyr
age
4.5 Gyr
8
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
9
Abrupt decay after 0.6 Gyr
Easy explanation of the
Vaughan Preston gap
10
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

11
Chromospheric Activity of 46 field stars 34
inactive, 4 intermediate, 8 active stars Active
ltt1 , t2ltintermediateltt2,inactivegtt2
12
(No Transcript)
13
(No Transcript)
14
(No Transcript)
15
(No Transcript)
16
(No Transcript)
17
(No Transcript)