J/A+A/627/A118 Optical activity indicators (Maldonado+, 2019)
Temporal evolution and correlations of optical activity indicators measured in
Sun-as-a-star observations.
Maldonado J., Phillips D.F., Dumusque X., Collier Cameron A., Haywood R.D.,
Lanza A.F., Micela G., Mortier A., Saar S.H., Sozzetti A., Rice K.,
Milbourne T., Cecconi M., Cegla H.M., Cosentino R., Costes J., Ghedina A.,
Gonzalez M., Guerra J., Hernandez N., Li C.-H., Lodi M., Malavolta L.,
Molinari E., Pepe F., Piotto G., Poretti E., Sasselov D., San Juan J.,
Thompson S., Udry S., Watson C.
<Astron. Astrophys. 627, A118 (2019)>
=2019A&A...627A.118M 2019A&A...627A.118M (SIMBAD/NED BibCode)
ADC_Keywords: Solar system ; Sun ; Spectroscopy ; Radial velocities
Keywords: Sun: activity - Sun: chromosphere - Sun: rotation -
techniques: spectroscopic
Abstract:
Understanding stellar activity in solar-type stars is crucial for the
physics of stellar atmospheres as well as for ongoing exoplanet
programmes.
We aim to test how well we understand stellar activity using our own
star, the Sun, as a test case.
We perform a detailed study of the main optical activity indicators
(CaII H & K, Balmer lines, NaI D1, D2, and HeI D3 measured for the Sun
using the data provided by the HARPS-N solar-telescope feed at the
Telescopio Nazionale Galileo. We make use of periodogram analyses to
study solar rotation, and we use the pool variance technique to study
the temporal evolution of active regions. The correlations between the
different activity indicators as well as the correlations between
activity indexes and the derived parameters from the cross-correlation
technique are analysed. We also study the temporal evolution of these
correlations and their possible relationship with indicators of
inhomogeneities in the solar photosphere like sunspot number or radio
flux values.
The value of the solar rotation period is found in all the activity
indicators, with the only exception being Hδ. The derived values
vary from 26.29 days (Hγ line) to 31.23 days (HeI). From an
analysis of sliding periodograms we find that in most of the activity
indicators the spectral power is split into several "bands" of periods
around 26 and 30 days, that might be explained by the migration of
active regions between the equator and a latitude of ∼30°, spot
evolution or a combination of both effects. In agreement with previous
works a typical lifetime of active regions of ∼ ten rotation periods
is inferred from the pooled variance diagrams. We find that Hα,
Hβ, Hγ, Hε, and HeI show a significant correlation
with the S index. Significant correlations between the contrast,
bisector span, and the heliocentric radial velocity with the activity
indexes are also found. We show that the full width at half maximum,
the bisector, and the disc-integrated magnetic field correlate with
the radial velocity variations. The correlation of the S index and
Hα changes with time, increasing with larger sun spot numbers and
solar irradiance. A similar tendency with the S index - radial
velocity correlation is also present in the data.
Our results are consistent with a scenario in which higher activity
favours the correlation between the S index and the Hα activity
indicators and between the S index and radial velocity variations.
Description:
File tableA.1.dat lists the daily median activity indexes and their
uncertainties as well as the daily median CCF parameters measured in
the Sun-as-a-star observations.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 266 821 Daily median activity indexes and CCF parameters
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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3- 14 F12.6 d BJD Barycentric Julain date (BJD-2400000)
18- 25 F8.6 km/s HRV Heliocentric radial velocity (1)
29- 34 E6.2 km/s e_HRV DRS Uncertainty on radial velocity
38- 45 F8.6 km/s FWHM Sidereal FWHM (2)
49- 57 F9.6 % Contrast DRS Contrast
61- 68 F8.5 km/s BIS DRS Bisector
72- 79 F8.6 --- S S index
84- 91 F8.6 --- Halpha Hα index
97-104 F8.6 --- Hbeta Hβ index
109-116 F8.6 --- Hgamma Hγ index
122-129 F8.6 --- Hdelta Hδ index
135-142 F8.6 --- Hepsilon Hε index
150-157 F8.6 --- He He 1 D3 index
165-172 F8.6 --- Na Na 1 D1, D2 index
181-188 E8.3 --- e_S Uncertainty on S index
194-200 E7.3 --- e_Halpha Uncertainty on Hα index
205-211 E7.3 --- e_Hbeta Uncertainty on Hβ index
216-222 E7.3 --- e_Hgamma Uncertainty on Hγ index
227-233 E7.3 --- e_Hdelta Uncertainty on Hδ index
238-244 E7.3 --- e_Hepsilon Uncertainty on Hε index
249-255 E7.3 --- e_He Uncertainty on He 1 D3 index
260-266 E7.3 --- e_Na Uncertainty on Na 1 D1, D2 index
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Note (1): Corrected from the motion of the Solar System's giant planets
(Jupiter and Saturn) by Cameron et al. (2019MNRAS.tmp.1180C).
Note (2): Corrected from the Earth orbital motion and solar ecliptic obliquity
by Cameron et al. (2019MNRAS.tmp.1180C)
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Acknowledgements:
Jesus Maldonado, jesus.maldonado(at)inaf.it
(End) Jesus Maldonado [INAF-OAPa, Italy, Patricia Vannier [CDS] 18-Jun-2019