The HADES RV Programme with HARPS-N at TNG

Pinamonti, M.; Damasso, M.; Marzari, F.; Sozzetti, A.; Desidera, S.; Maldonado, J.; Scandariato, G.; Affer, L.; Lanza, A. F.; Bignamini, A.; Bonomo, A. S.; Borsa, F.; Claudi, R.; Cosentino, R.; Giacobbe, P.; González-Álvarez, E.; Hernández, J. I. González; Gratton, R.; Leto, G.; Malavolta, L.; Fiorenzano, A. Martinez; Micela, G.; Molinari, E.; Pagano, I.; Pedani, M.; Perger, M.; Piotto, G.; Rebolo, R.; Ribas, I.; Mascareño, A. Suárez; Toledo-Padrón, B.

doi:10.1051/0004-6361/201732535

Cited by 45 publications

(44 citation statements)

References 58 publications

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“…The super-Earth planet around GJ 338 B adds to the increasing list of planets orbiting one of the stars of stellar binary systems. We remark the similarity of the two stellar components of the GJ 338 binary and also provide various existing examples with very similar components such as: WASP-2 AB, XO-2N, XO-2S, HD 177830 AB, Kepler 296 AB, WASP-94 AB and Gliese 15 AB (Collier Cameron et al 2007;Torres et al 2008;Meschiari et al 2011;Desidera et al 2014;Rowe et al 2014;Neveu-VanMalle et al 2014;Pinamonti et al 2018).…”

Section: Discussionmentioning

confidence: 55%

The CARMENES search for exoplanets around M dwarfs

González-Álvarez

Osorio

Caballero

et al. 2020

A&A

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Aims. We report on radial velocity time series for two M0.0 V stars, GJ 338 B and GJ 338 A, using the CARMENES spectrograph, complemented by ground-telescope photometry from Las Cumbres and Sierra Nevada observatories. We aim to explore the presence of small planets in tight orbits using the spectroscopic radial velocity technique. Methods. We obtained 159 and 70 radial velocity measurements of GJ 338 B and A, respectively, with the CARMENES visible channel between 2016 January and 2018 October. We also compiled additional relative radial velocity measurements from the literature and a collection of astrometric data that cover 200 a of observations to solve for the binary orbit. Results. We found dynamical masses of 0.64 ± 0.07 M for GJ 338 B and 0.69 ± 0.07 M for GJ 338 A. The CARMENES radial velocity periodograms show significant peaks at 16.61 ± 0.04 d (GJ 338 B) and 16.3 +3.5 −1.3 d (GJ 338 A), which have counterparts at the same frequencies in CARMENES activity indicators and photometric light curves. We attribute these to stellar rotation. GJ 338 B shows two additional, significant signals at 8.27 ± 0.01 and 24.45 ± 0.02 d, with no obvious counterparts in the stellar activity indices. The former is likely the first harmonic of the star's rotation, while we ascribe the latter to the existence of a super-Earth planet with a minimum mass of 10.27 +1.47 −1.38 M ⊕ orbiting GJ 338 B. We have not detected signals of likely planetary origin around GJ 338 A. Conclusions. GJ 338 Bb lies inside the inner boundary of the habitable zone around its parent star. It is one of the least massive planets ever found around any member of stellar binaries. The masses, spectral types, brightnesses, and even the rotational periods are very similar for both stars, which are likely coeval and formed from the same molecular cloud, yet they differ in the architecture of their planetary systems.

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Section: Discussionmentioning

confidence: 55%

The CARMENES search for exoplanets around M dwarfs

González-Álvarez

Osorio

Caballero

et al. 2020

A&A

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“…To mitigate the stellar activity signal in the RV time series, and to test the statistical significance of a dynamical model including one planet over the "null hypothesis" case, where only an activity term is considered, we have defined a Bayesian framework based on a Monte Carlo (MC) sampling of the parameter space. The stellar activity term has been treated as a quasi-periodic signal through a Gaussian process (GP) regression, a technique commonly used to detect or characterize many exoplanetary systems (Haywood et al 2014), also within the HADES collaboration (Affer et al 2016;Perger et al 2017b;Pinamonti et al 2018).…”

Section: Monte Carlo Analysis Of the Rv Time Series Based On Gaussianmentioning

confidence: 99%

“…We present high-precision, high-resolution spectroscopic measurements of the bright M1 dwarf Gl 686, gathered with the HARPS-N spectrograph (Cosentino et al 2012) on the Telescopio Nazionale Galileo (TNG) as part of the HArps-n red Dwarf Exoplanet Survey (HADES) 1 , described in detail in Affer et al (2016). The HADES collaboration has already produced many valuable results, regarding the statistics, activity, and characterization of M stars (Perger et al 2017a;Maldonado et al 2015Maldonado et al , 2017Scandariato et al 2017;Suárez Mascareño et al 2018), and has led to the discovery of several planets (Affer et al 2016;Suárez Mascareño et al 2017;Perger et al 2017b;Pinamonti et al 2018).…”

Section: Introductionmentioning

confidence: 99%

HADES RV program with HARPS-N at the TNG

Affer

Damasso

Micela

et al. 2019

A&A

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Aims. The HArps-n red Dwarf Exoplanet Survey (HADES) is providing a major contribution to the widening of the current statistics of low-mass planets, through the in-depth analysis of precise radial-velocity (RV) measurements in a narrow range of spectral sub-types. Using the HARPS-N spectrograph we reach the precision needed to detect small planets with a few earth masses. Our survey is mainly focused on the M-dwarf population of the northern hemisphere. Methods. As part of that program, we obtained RV measurements of Gl 686, an M1 dwarf at d = 8.2 pc. These measurements show a dispersion much in excess of their internal errors. The analysis of data obtained within an intensive observing campaign demonstrates that the excess dispersion is due to a coherent signal with a period of 15.53 d. Almost simultaneous photometric observations were carried out within the APACHE and EXORAP programs to characterize the stellar activity and to distinguish periodic variations related to activity from signals due to the presence of planetary companions, complemented also with ASAS photometric data. We used a Bayesian framework to estimate the orbital parameters and the planet minimum mass, and to properly treat the activity noise. We took advantage of the available RV measurements for this target from other observing campaigns. The analysis of the RV composite time series from the HIRES, HARPS, and HARPS-N spectrographs, consisting of 198 measurements taken over 20 yr, enabled us to address the nature of periodic signals and also to characterize stellar physical parameters (mass, temperature, and rotation). Results. We report the discovery of a super-Earth orbiting at a distance of 0.092 AU from the host star Gl 686. The planet has a minimum mass of 7.1 ± 0.9 M⊕ and an orbital period of 15.532 ± 0.002 d. The analysis of the activity indexes, of the correlated noise through a Gaussian process framework, and of the photometry provides an estimate of the stellar rotation period at 37 d, and highlights the variability of the spot configuration during the long timespan covering 20 yr. The observed periodicities around 2000 d likely point to the existence of an activity cycle.

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“…The quasi-periodic GP model is often used to effectively correct (mitigate) the stellar activity term in RV time series that contain signals modulated on P rot (e.g. Affer et al 2016;Damasso & Del Sordo 2017;Pinamonti et al 2018), and the effective use of GP models in recovering small-amplitude planetary signals was demonstrated for the case of synthetic RV time series (e.g. Dumusque et al 2017).…”

Section: Stellar Activity Modelmentioning

confidence: 99%

“…For instance, several examples exist of RV datasets we have analysed using a quasi-periodic GP model for which estimates of τ AR have values close to P rot (e.g. Damasso et al 2018;Pinamonti et al 2018;Haywood et al 2018;Malavolta et al 2018). On the other hand, other studies cast doubts on this hypothesis, stating that much longer time scales solutions should be more physically valid, especially for M dwarfs (e.g.…”

Section: Stellar Activity Modelmentioning

confidence: 99%

Biases in retrieving planetary signals in the presence of quasi-periodic stellar activity

Damasso

Pinamonti

Scandariato

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Gaussian process regression is a widespread tool used to mitigate stellar correlated noise in radial velocity time series. It is particularly useful to search for and determine the properties of signals induced by small-size, low-mass planets (R < 4R ⊕ , m < 10M ⊕ ). By using extensive simulations based on a quasi-periodic representation of the stellar activity component, we investigate the ability in retrieving the planetary parameters in 16 different realistic scenarios. We analyse systems composed by one planet and host stars having different levels of activity, focusing on the challenging case represented by low-mass planets, with Doppler semi-amplitudes in the range 1-3 m s −1 ). We consider many different configurations for the quasi-periodic stellar activity component, as well as different combinations of the observing epochs. We use commonly-employed analysis tools to search for and characterize the planetary signals in the datasets. The goal of our injection-recovery statistical analysis is twofold. First, we focus on the problem of planet mass determination. Then, we analyse in a statistical way periodograms obtained with three different algorithms, in order to explore some of their general properties, as the completeness and reliability in retrieving the injected planetary and stellar activity signals with low false alarm probabilities. This work is intended to provide some understanding of the biases introduced in the planet parameters inferred from the analysis of radial velocity time series that contain correlated signals due to stellar activity. It also aims to motivate the use and encourage the improvement of extensive simulations for planning spectroscopic follow-up observations.

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The HADES RV Programme with HARPS-N at TNG

Cited by 45 publications

References 58 publications

The CARMENES search for exoplanets around M dwarfs

The CARMENES search for exoplanets around M dwarfs

HADES RV program with HARPS-N at the TNG

Biases in retrieving planetary signals in the presence of quasi-periodic stellar activity

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