HADES RV Programme with HARPS-N at TNG

Scandariato, G.; Maldonado, J.; Affer, L.; Biazzo, K.; Leto, G.; Stelzer, B.; Sánchez, R. Zanmar; Claudi, R.; Cosentino, R.; Damasso, M.; Desidera, S.; Álvarez, E. González; Hernández, J. I. González; Gratton, R.; Lanza, A. F.; Maggio, A.; Messina, S.; Micela, G.; Pagano, I.; Perger, M.; Piotto, G.; Rebolo, R.; Ribas, I.; Rosich, A.; Sozzetti, A.; Mascareño, A. Suárez

doi:10.1051/0004-6361/201629382

Cited by 38 publications

(46 citation statements)

References 47 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In order to study the temporal evolution of active regions we made use of the pooled variance technique (Donahue et al 1997a,b;Lanza et al 2004;Scandariato et al 2017). In brief, for a given time interval, t, the data are binned into segments of length t, and the average variance of the set of these segments is computed.…”

Section: Temporal Evolution Of Active Regionsmentioning

confidence: 99%

Temporal evolution and correlations of optical activity indicators measured in Sun-as-a-star observations

Maldonado

Phillips

Dumusque

et al. 2019

A&A

Self Cite

View full text Add to dashboard Cite

Context. Understanding stellar activity in solar-type stars is crucial for the physics of stellar atmospheres as well as for ongoing exoplanet programmes. Aims. We aim to test how well we understand stellar activity using our own star, the Sun, as a test case. Methods. We perform a detailed study of the main optical activity indicators (Ca ii H & K, Balmer lines, Na i D 1 D 2 , and He i D 3 ) 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. Results. 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 (He i). 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, H , and He i 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. Conclusions. 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.

show abstract

Section: Temporal Evolution Of Active Regionsmentioning

confidence: 99%

Temporal evolution and correlations of optical activity indicators measured in Sun-as-a-star observations

Maldonado

Phillips

Dumusque

et al. 2019

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…For stars with more than one observation, spectra were combined into one single spectrum following the procedure described in Scandariato et al (2017). In the following we refer to the combined spectra unless otherwise noted.…”

Section: Stellar Samplementioning

confidence: 99%

“…An extensive description of the procedure adopted to compute the excess fluxes is provided by Scandariato et al (2017). Here we give a summary of the reduction steps that lead to the measurement of the flux excess.…”

Section: Emission Excess Fluxesmentioning

confidence: 99%

“…This might be related to the complex mechanisms involved in the Hα emission. We considered emission excesses in the subtracted spectrum, and it was shown that at relatively low-activity levels (such as the ones in our sample) the flux radiated in the Hα line seems to initially decrease with increasing calcium flux, resulting in an Hα extra-absorption (Robinson et al 1990;Walkowicz & Hawley 2009;Scandariato et al 2017). …”

Section: Emission Excess Fluxesmentioning

confidence: 99%

“…In this paper we focus on average trends, while the short-term chromospheric variability of the sample is studied in a companion paper (Scandariato et al 2017). This paper is organised as follows.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

HADES RV Programme with HARPS-N at TNG

Maldonado

Scandariato

Stelzer

et al. 2017

A&A

Self Cite

View full text Add to dashboard Cite

Context. Understanding stellar activity in M dwarfs is crucial for the physics of stellar atmospheres and for ongoing radial velocity exoplanet programmes. Despite the increasing interest in M dwarfs, our knowledge of the chromospheres of these stars is far from being complete. Aims. We test whether the relations between activity, rotation, and stellar parameters and flux-flux relationships previously investigated for main-sequence FGK stars and for pre-main-sequence M stars also hold for early-M dwarfs on the main-sequence. Although several attempts have been made so far, here we analyse a large sample of stars undergoing relatively low activity. Methods. We analyse in a homogeneous and coherent way a well-defined sample of 71 late-K/early-M dwarfs that are currently being observed in the framework of the HArps-N red Dwarf Exoplanet Survey (HADES). Rotational velocities are derived using the cross-correlation technique, while emission flux excesses in the Ca ii H & K and Balmer lines from Hα up to H are obtained by using the spectral subtraction technique. The relationships between the emission excesses and the stellar parameters (projected rotational velocity, effective temperature, kinematics, and age) are studied. Relations between pairs of fluxes of different chromospheric lines (flux-flux relationships) are also studied and compared with the literature results for other samples of stars.Results. We find that the strength of the chromospheric emission in the Ca ii H & K and Balmer lines is roughly constant for stars in the M0-M3 spectral range. Although our sample is likely to be biased towards inactive stars, our data suggest that a moderate but significant correlation between activity and rotation might be present, as well as a hint of kinematically selected young stars showing higher levels of emission in the calcium line and in most of the Balmer lines. We find our sample of M dwarfs to be complementary in terms of chromospheric and X-ray fluxes with those of the literature, extending the analysis of the flux-flux relationships to the very low flux domain. Conclusions. Our results agree with previous works suggesting that the activity-rotation-age relationship known to hold for solar-type stars also applies to early-M dwarfs. We also confirm previous findings that the field stars which deviate from the bulk of the empirical flux-flux relationships show evidence of youth.

show abstract