Bibcode
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.; Molinari, E.; 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.
Bibliographical reference
Astronomy and Astrophysics, Volume 616, id.A155, 16 pp.
Advertised on:
9
2018
Journal
Citations
30
Refereed citations
27
Description
Aims: 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 log
R'HK in detecting RV variations induced by stellar
activity in 15 slowly rotating (υ sin i ≤ 5 km s-1),
weakly active (log R'HK ≤ -4.95) solar-like
stars observed with the high-resolution spectrograph High Accuracy
Radial velocity Planet Searcher for the Northern hemisphere (HARPS-N).
Methods: 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. Results: 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
υ sin i 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.
Based on observations made with the Italian Telescopio Nazionale Galileo
(TNG) operated on the island of La Palma by the Fundación Galileo
Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish
Observatorio del Roque de los Muchachos of the Instituto de
Astrofísica de Canarias.The IDL macro to compute the line profile
indicators is also available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr
(ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/616/A155