J/A+A/619/A73 Solar Twins age-chromospheric activity (Lorenzo-Oliveira+, 2018)
The Solar Twin Planet Search. VI. The age-chromospheric activity relation.
Lorenzo-Oliveira D., Freitas F., Melendez J., Bedell M., Ramirez I.,
Bean J., Asplund M., Spina L., Dreizler S., Alves-Brito A., Casagrande L.
<Astron. Astrophys. 619, A73 (2018)>
=2018A&A...619A..73L 2018A&A...619A..73L (SIMBAD/NED BibCode)
ADC_Keywords: Stars, G-type ; Magnetic fields ; Effective temperatures ;
Abundances, [Fe/H]; Stars, ages
Keywords: stars: solar-type - stars: evolution - stars: fundamental parameters -
magnetic fields
Abstract:
It is well known that the magnetic activity of solar-type stars
decreases with age, but it is widely debated in the literature whether
there is a smooth decline or if there is an early sharp drop until
1-2Gyr that is followed by a relatively inactive constant phase.
We revisited the activity-age relation using time-series observations
of a large sample of solar twins whose precise isochronal ages and
other important physical parameters have been determined.
We measured the CaII H and K activity indices using 9000 HARPS
spectra of 82 solar twins. In addition, the average solar activity was
calculated through asteroids and Moon reflection spectra using the
same instrumentation. Thus, we transformed our activity indices into
the S Mount Wilson scale (SMW), recalibrated the Mount Wilson
absolute flux and photospheric correction equations as a function of
Te, and then computed an improved bolometric flux normalized activity
index logR'HK(Teff) for the entire sample.
New relations between activity and the age of solar twins were derived
by assessing the chromospheric age-dating limits using logR'HK(Teff).
We measured an average solar activity of SMW=0.1712±0.0017 during
solar magnetic cycles 23-24 covered by HARPS observations, and we
also inferred an average of SMW=0.1694±0.0025 for cycles 10-24,
anchored on a sunspot number correlation of S index versus. We also
found a simple relation between the average and the dispersion of the
activity levels of solar twins. This enabled us to predict the stellar
variability effects on the age-activity diagram, and consequently, to
estimate the chromospheric age uncertainties that are due to the same
phenomena. The age-activity relation is still statistically
significant up to ages around 6-7Gyr, in agreement with previous works
using open clusters and field stars with precise ages.
Our research confirms that CaII H& K lines remain a useful
chromospheric evolution tracer until stars reach ages of at least
6-7Gyr. We found evidence that for the most homogenous set of old
stars, the chromospheric activity indices seem to continue to decrease
after the solar age toward the end of the main sequence. Our results
indicate that a significant part of the scatter observed in the
age-activity relation of solar twins can be attributed to stellar
cycle modulations eects. The Sun seems to have a normal activity level
and variability for its age.
Description:
Our sample was selected from the 88 solar twins presented in Ramirez
et al. (2014A&A...572A..48R 2014A&A...572A..48R). From this sample, we obtained data for
70 stars with the HARPS instrument (Mayor et al., 2003Msngr.114...20M 2003Msngr.114...20M)
at the 3.6 m telescope at the La Silla observatory, to search for
planets around solar twins (program 188.C-0265, Bedell et al.,
2015A&A...581A..34B 2015A&A...581A..34B; Melendez et al., 2015Msngr.161...28M 2015Msngr.161...28M,
2017A&A...597A..34M 2017A&A...597A..34M). Additional data for 12 stars were found in the
ESO archive.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 136 82 All the solar twins observed by HARPS, their
respective programs and S values compiled from
the literature
table2.dat 111 82 Parameters of all sample solar twins
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See also:
III/159 : Ca II H and K Measurements Made at MWO (Duncan+ 1991)
J/AJ/111/439 : Chromospheric emission in late-type stars. (Henry+ 1996)
J/ApJS/152/261 : Chromospheric Ca II emission in nearby stars (Wright+, 2004)
J/MNRAS/372/163 : Activity indices for southern stars (Jenkins+, 2006)
J/A+A/531/A8 : Activity indices & velocities for 890 stars (Jenkins+, 2011)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 6 I6 --- HIP HIP number
7 A1 --- n_HIP [*] Note on HIP (G1)
9-114 A106 --- ESO ESO programs
116-120 F5.3 --- S ? CaII H and K activity S-index
122-126 F5.3 --- e_S ? rms uncertainty on S
128-136 A9 --- r_S Reference for S value (1)
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Note (1): References as follows:
1 = Ramirez et al. (2014A&A...572A..48R 2014A&A...572A..48R)
2 = Jenkins et al. (2011, Cat. J/A+A/531/A8)
3 = Jenkins et al. (2006, Cat. J/MNRAS/372/163)
4 = Wright et al. (2004, Cat. J/ApJS/152/261)
5 = Henry et al. (1996, Cat. J/AJ/111/439)
6 = Duncan et al. (1991ApJS...76..383D 1991ApJS...76..383D, Cat. III/159)
7 = Melendez et al. (2009ApJ...704L..66M 2009ApJ...704L..66M)
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 I6 --- HIP HIP number
7 A1 --- n_HIP [*] Note on HIP (G1)
9- 13 F5.3 mag Vmag V magnitude
15- 19 F5.3 mag e_Vmag ? rms uncertainty on Vmag
21- 25 F5.3 mag B-V ? B-V colour index
27- 31 F5.3 mag e_B-V ? rms uncertainty on B-V
33- 36 I4 K Teff Effective temperature
38- 39 I2 K e_Teff ? rms uncertainty on Teff
41- 45 F5.3 [cm/s2] logg ? Surface gravity
47- 51 F5.3 [cm/s2] e_logg ? rms uncertainty on logg
53- 58 F6.3 [-] [Fe/H] ? Metallicity
60- 64 F5.3 [-] e_[Fe/H] ? rms uncertainty on [Fe/H]
66- 70 F5.3 --- SMW Mount Wildson CaII H and K activity
S-index, SMW
72- 76 F5.3 --- e_SMW rms uncertainty on SMW
78- 83 F6.3 --- logR'HK(Teff) logR'HK activity index (from Teff)
85- 89 F5.3 --- e_logR'HK(Teff) rms uncertainty on logR'HK(Teff)
91- 93 F3.1 Gyr Age ? Age
95- 97 F3.1 Gyr E_Age ? Error on Age (upper limit)
99-101 F3.1 Gyr e_Age ? Error on Age (lower limit)
103-106 I4 --- NObs Number of observations
108-111 F4.1 yr Time Time-span
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Global notes:
Note (G1): *: Spectroscopic binary
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History:
From electronic version of the journal
References:
Ramirez et al., Paper I 2014A&A...572A..48R 2014A&A...572A..48R
Bedell et al., Paper II 2015A&A...581A..34B 2015A&A...581A..34B
Tucci Maia et al., Paper III 2016A&A...590A..32T 2016A&A...590A..32T
dos Santos et al., Paper IV 2016A&A...592A.156D 2016A&A...592A.156D
Melendez et al., Paper V 2017A&A...597A..34M 2017A&A...597A..34M
(End) Patricia Vannier [CDS] 06-Nov-2018