J/A+A/616/A155 Code to compute spectral line profile indicators (Lanza+, 2018)
The GAPS Programme with HARPS-N at TNG:
XVII. Line profile indicators and kernel regression as diagnostics of
radial-velocity variations due to stellar activity in solar-like stars.
Lanza A.F., Malavolta L., Benatti S., Desidera S., Bignamini A.,
Bonomo A.S., Esposito M., Figueira P., Gratton R., Scandariato G.,
Damasso M., Sozzetti A., Biazzo K., Claudi R.U., Cosentino R., Covino E.,
Maggio A., Masiero S., Micela G., Pagano I., Piotto G., Poretti E.,
Smareglia R., Affer L., Boccato C., Borsa F., Boschin W., Giacobbe P.,
Knapic C., Leto G., Maldonado J., Mancini L., Martinez Fiorenzano A.,
Messina S., Nascimbeni V., Pedani M., Rainer M.
<Astron. Astrophys. 616, A155 (2018)>
=2018A&A...616A.155L 2018A&A...616A.155L (SIMBAD/NED BibCode)
ADC_Keywords: Models ; Line Profiles
Keywords: planetary systems - stars: activity - stars: late-type - starspots -
stars: atmospheres - techniques: radial velocities
Abstract:
Stellar activity is the ultimate source of radial-velocity
(hereinafter RV) noise in the search for Earth-mass planets orbiting
late-type main-sequence stars. We analyse the performance of four
different indicators and the chromospheric index logR'HK in
detecting RV variations induced by stellar activity in 15 slowly
rotating vsini≤5km/s), weakly active (logR'HK≤-4.95) solar-like
stars observed with the high-resolution spectrograph High Accuracy
Radial velocity Planet Searcher for the Northern hemisphere (HARPS-N).
We consider indicators of the asymmetry of the cross-correlation
function (CCF) between the stellar spectrum and the binary weighted
line mask used to compute the RV, that is the bisector inverse span
(BIS), ΔV, and a new indicator Vasy(mod) together with the
full width at half maximum (FWHM) of the CCF. We present methods to
evaluate the uncertainties of the CCF indicators and apply a kernel
regression (KR) between the RV, the time, and each of the indicators
to study their capability of reproducing the RV variations induced by
stellar activity. The considered indicators together with the KR prove
to be useful to detect activity-induced RV variations in
∼47±18 percent of the stars over a two-year time span when a
significance (two-sided p-value) threshold of one percent is adopted.
In those cases, KR reduces the standard deviation of the RV time
series by a factor of approximately two. The BIS, the FWHM, and the
newly introduced Vasy(mod) are the best indicators, being
useful in 27±13, 13±9, and 13±9 percent of the cases,
respectively. The relatively limited performances of the activity
indicators are related to the very low activity level and vsini
of the considered stars. For the application of our approach to
sun-like stars, a spectral resolution allowing
λ/Δλ≥105 and highly stabilized spectrographs
are recommended.
Description:
A computer code (procedure) written in Interactive Data Language (IDL)
to compute the spectral line profile indicators used in the above
research article starting from the fits files provided by the data
reduction software (DRS) of HARPS or HARPS-N. The procedure takes the
cross-correlation function (CCF) files provided by the DRS as an
input.
An example for the input files and the corresponding output file is
provided with the sole purpose of allowing to test the proper
compilation and running of the procedure. Details on an auxiliary
source file (mpfit.pro) required for compilation are provided in the
header of the procedure file and in Appendix A of the above mentioned
article. Interested users are warmly recommended to read them before
compiling and running the procedure.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
asym_ind.pro 242 1697 IDL procedure
input/* . 118 Directory containing example input FITS files
output.dat 470 56 Example output file
mpfit.pro 95 3737 *Auxiliary IDL procedure for compilation
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Note on mpfit.pro: The IDL procedure mpfit.pro was authored by Craig B.
Markwardt, NASA/GSFC Code 662, Greenbelt, MD 20770 and is accessible at the
URL http://cow.physics.wisc.edu/~craigm/idl/fitting.html
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Description of file: input/*
This directory contains the 116 FITS files used to produce the example
output file by running the IDL procedure asym_ind.pro. This procedure
reads the input files, the names of which are listed in the auxiliary
text files flistccf.lis and flistbis.lis, computes the line indicators
for their CCFs and print the results in the output file. These FITS
files were produced by the DRS running on HARPS-N observations of the
star HD 108874. Details on the observations, the spectrograph, and the
data reduction procedure are provided in Benatti et al.
(2017A&A...599A..90B 2017A&A...599A..90B).
Byte-by-byte Description of file: output.dat
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Bytes Format Units Label Explanations
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2- 21 F20.8 d Time Solar system barycentric JD (time) (1)
22- 41 F20.8 km/s RV Radial velocity (rv)
42- 61 F20.8 km/s e_RV Error on radial velocity (e_rv)
62- 70 I9 --- maxcpp Maximum number of counts per pixel (maxcpp)
71- 90 F20.8 km/s BIS Line bisector slope (bis)
91-110 F20.8 km/s e_BIS Error on line bisector slope (e_bis)
111-130 F20.8 km/s deltav deltav indicator (delta_v)
131-150 F20.8 km/s e_deltav Error on deltav indicator (edeltav)
151-170 F20.8 --- vasy Vasy indicator of Figuera et al.
(2013A&A...557A..93F 2013A&A...557A..93F) (vasy)
171-190 F20.8 --- e_vasy Error on the vasy of Figueira et al.
(2013A&A...557A..93F 2013A&A...557A..93F) (e_vasy)
191-210 F20.8 --- vasymod Modified vasy indicator (present work)
(vasymod)
211-230 F20.8 --- e_vasymod Error of vasymod (e_vasymod)
231-250 F20.8 km/s FWHMdrs FWHM as given by the DRS (fwhmdrs)
251-270 F20.8 km/s FWHMfit FWHM as given by a Gaussian fit to CCF
(fwhmfit)
271-290 F20.8 km/s e_FWHM Error on FWHM computed by mpfit.pro (e_fwhm)
291-310 F20.8 --- cont-drs CCF contrast given by the DRS (cont_drs)
311-330 F20.8 --- contrast CCF contrast computed by mpfit.pro (contrast)
331-350 F20.8 --- e_contr Error on the CCF contrast by mpfit.pro
(e_contr)
351-370 F20.8 km/s FWHMs Median FWHM of 200 CCF realizations (fwhm_s)
371-390 F20.8 km/s e_FWHMs Error of fwhms (efwhms)
391-410 F20.8 km/s deltavs Median delta_v of 200 CCF realizations
(delta_vs)
411-430 F20.8 km/s e_deltavs Error on deltavs (edeltavs)
431-450 F20.8 --- conts Median contrast of 200 CCF realizations
(cont_s)
451-470 F20.8 --- e_conts Error on conts (econts)
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Note (1): For a full explanation of the various fields of the output file, see
the header of the IDL procedure asym_ind.pro.
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Acknowledgements:
Antonino Francesco Lanza, nuccio.lanza(at)oact.inaf.it
References:
Covino et al., Paper I 2013A&A...554A..28C 2013A&A...554A..28C, Cat. J/A+A/554/A28
Desidera et al., Paper II 2013A&A...554A..29D 2013A&A...554A..29D
Esposito et al., Paper III 2014A&A...564L..13E 2014A&A...564L..13E
Desidera et al., Paper IV 2014A&A...567L...6D 2014A&A...567L...6D
Damasso et al., Paper V 2015A&A...575A.111D 2015A&A...575A.111D, Cat. J/A+A/575/A111
Sozzetti et al., Paper VI 2015A&A...575L..15S 2015A&A...575L..15S, Cat. J/A+A/575/L15
Borsa et al., Paper VII 2015A&A...578A..64B 2015A&A...578A..64B, Cat. J/A+A/578/A64
Mancini et al., Paper VIII 2015A&A...579A.136M 2015A&A...579A.136M, Cat. J/A+A/579/A136
Damasso et al., Paper IX 2015A&A...581L...6D 2015A&A...581L...6D,
Biazzo et al., Paper X 2015A&A...583A.135B 2015A&A...583A.135B, Cat. J/A+A/583/A135
Malavolta et al., Paper XI 2016A&A...588A.118M 2016A&A...588A.118M, Cat. J/A+A/588/A118
Benatti et al., Paper XII 2017A&A...599A..90B 2017A&A...599A..90B, Cat. J/A+A/599/A90
Esposito et al., Paper XIII 2017A&A...601A..53E 2017A&A...601A..53E
Bonomo et al., Paper XIV 2017A&A...602A.107B 2017A&A...602A.107B, Cat. J/A+A/602/A107
Gonzalez-Alvarez et al., Paper XV 2017A&A...606A..51G 2017A&A...606A..51G
(End) Antonino F. Lanza [INAF, Italy], Patricia Vannier [CDS] 18-Apr-2018