The APACHE Project

Sozzetti, A.; Bernagozzi, A.; Bertolini, E.; Calcidese, P.; Carbognani, A.; Cenadelli, Davide; Christille, J. M.; Damasso, M.; Giacobbe, P.; Lanteri, L.; Lattanzi, M. G.; Smart, R. L.

doi:10.1051/epjconf/20134703006

Cited by 35 publications

(29 citation statements)

References 33 publications

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“…Furthermore, M dwarfs have become the most promising ground for the hunt for low-mass, rocky planets (e.g. Dressing & Charbonneau 2013;Sozzetti et al 2013;Astudillo-Defru et al 2017b), due to their more advantageous mass and radius ratios compared to solar-type stars. There is a solid evidence, arising both from HARPS and Kepler observations, that super Earths and Neptunes are commonly found in multiple systems (e.g.…”

Section: Introductionmentioning

confidence: 99%

The HADES RV Programme with HARPS-N at TNG

Pinamonti

Damasso

Marzari

et al. 2018

A&A

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We present 20 yr of radial velocity (RV) measurements of the M1 dwarf Gl15A, combining five years of intensive RV monitoring with the HARPS-N spectrograph with 15 yr of archival HIRES/Keck RV data. We have carried out an MCMC-based analysis of the RV time series, inclusive of Gaussian Process (GP) approach to the description of stellar activity induced RV variations. Our analysis confirms the Keplerian nature and refines the orbital solution for the 11.44-day period super Earth, Gl15A b, reducing its amplitude to 1.68, and successfully models a long-term trend in the combined RV dataset in terms of a Keplerian orbit with a period around 7600 days and an amplitude of 2.5, corresponding to a super-Neptune mass (M sin i = 36 +25 −18 M ⊕ ) planetary companion. We also discuss the present orbital configuration of Gl15A planetary system in terms of the possible outcomes of Lidov-Kozai interactions with the wide-separation companion Gl15B in a suite of detailed numerical simulations. In order to improve the results of the dynamical analysis, we have derived a new orbital solution for the binary system, combining our RV measurements with astrometric data from the WDS catalogue. The eccentric Lidov-Kozai analysis shows the strong influence of Gl15B on the Gl15A planetary system, which can produce orbits compatible with the observed configuration for initial inclinations of the planetary system between 75• and 90• , and can also enhance the eccentricity of the outer planet well above the observed value, even resulting in orbital instability, for inclinations around 0• and 15• −30• . The Gl15A system is the multi-planet system closest to Earth, at 3.56 pc, and hosts the longest period RV sub-Jovian mass planet discovered so far. Its orbital architecture constitutes a very important laboratory for the investigation of formation and orbital evolution scenarios for planetary systems in binary stellar systems.

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Section: Introductionmentioning

confidence: 99%

The HADES RV Programme with HARPS-N at TNG

Pinamonti

Damasso

Marzari

et al. 2018

A&A

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“…Exoplanet transit surveys like MEarth (Nutzman & Charbonneau 2008;Irwin et al 2015), TRAPPIST (Gillon et al 2011), and APACHE (Sozzetti et al 2014) are currently targeting individual, nearby stars. In the near future, additional surveys like ExTrA (Bonfils et al 2015) will come online and also target the nearby M dwarfs.…”

Section: Introductionmentioning

confidence: 99%

A Search for Additional Bodies in the GJ 1132 Planetary System from 21 Ground-based Transits and a 100-hr Spitzer Campaign

Dittmann

Irwin

Charbonneau

et al. 2017

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We present the results of a search for additional bodies in the GJ 1132 system through two methods: photometric transits and transit timing variations of GJ 1132b. We collected 21 transit observations of GJ 1132b with the MEarth-South array. We obtained 100 near-continuous hours of observations with the Spitzer Space Telescope, including two transits of GJ 1132b and spanning 60% of the orbital phase of the maximum (6.9-day) period at which bodies coplanar with GJ 1132b would transit. We exclude transits of additional Mars-sized bodies, such as a second planet or a moon, with a confidence of 99.7%. We find that the planet-to-star radius ratio inferred from the MEarth and Spitzer light curves are discrepant at the 3.7s level, which we ascribe to the effects of starspots and faculae. When we combine the mass estimate of the star (obtained from its parallax and apparent K s band magnitude) with the stellar density inferred from our high-cadence Spitzer light curve (assuming zero eccentricity), we measure the stellar radius of GJ 1132 to be R 0.2105 0.0085 0.0102 -+  , and we refine the radius measurement of GJ 1132b to R 1.130 0.056  Å . Combined with HARPS RV measurements, we determine the density of GJ 1132b to be 6.2±2.0 g cm −3 . We refine the ephemeris of the system (improving the period determination by an order of magnitude) and find no evidence for transit timing variations, which would be expected if there was a second planet near an orbital resonance with GJ 1132b.

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“…Dressing & Charbonneau 2013;Sozzetti et al 2013). In particular, the radial velocity searches currently ongoing with HARPS at La Silla and in the framework of the Global Architecture of Planetary Systems project 1 (GAPS; Covino et al 2013) at the Telescopio Nazionale Galileo (TNG) with HARPS-N produce a large quantity of spectra with high resolution and a high signalto-noise ratio.…”

Section: Introductionmentioning

confidence: 99%

Stellar parameters of early-M dwarfs from ratios of spectral features at optical wavelengths

Maldonado

Affer

Micela

et al. 2015

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Context. Low-mass stars have been recognised as promising targets in the search for rocky, small planets with the potential of supporting life. As a consequence, Doppler search programmes using high-resolution spectrographs like HARPS or HARPS-N are providing huge quantities of optical spectra of M dwarfs. However, determining the stellar parameters of M dwarfs using optical spectra has proven to be challenging. Aims. We aim to calibrate empirical relationships to determine accurate stellar parameters for early-M dwarfs (spectral types M0-M4.5) using the same spectra as those that are used for radial velocity determinations, without the necessity of acquiring IR spectra or relying on atmospheric models and/or photometric calibrations. Methods. Our methodology consists of using ratios of pseudo-equivalent widths of spectral features as a temperature diagnostic, a technique frequently used in solar-type stars. Stars with effective temperatures obtained from interferometric estimates of their radii are used as calibrators. Empirical calibrations for the spectral type are also provided. Combinations of features and ratios of features are used to derive calibrations for the stellar metallicity. Our methods are then applied to a large sample of M dwarfs that are currently being observed in the framework of the HARPS GTO search for extrasolar planets. The derived temperatures and metallicities are used together with photometric estimates of mass, radius, and surface gravity to calibrate empirical relationships for these parameters. Results. A long list of spectral features in the optical spectra of early-M dwarfs was identified. This list shows that the pseudoequivalent width of roughly 43% of the features is strongly anticorrelated with the effective temperature. The correlation with the stellar metallicity is weaker. A total of 112 temperature sensitive ratios were identified and calibrated over the range 3100−3950 K, providing effective temperatures with typical uncertainties of about 70 K. Eighty-two ratios of pseudo-equivalent widths of features were calibrated to derive spectral types within 0.5 subtypes for stars with spectral types between K7V and M4.5V. We calibrated 696 combinations of the pseudo-equivalent widths of individual features and temperature-sensitive ratios for the stellar metallicity over a metallicity range from −0.54 to +0.24 dex, with estimated uncertainties in the range of 0.07−0.10 dex. We provide our own empirical calibrations for stellar mass, radius, and surface gravity. These parameters depend on the stellar metallicity. For a given effective temperature, lower metallicities predict lower masses and radii as well as higher gravities.

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The APACHE Project

Cited by 35 publications

References 33 publications

The HADES RV Programme with HARPS-N at TNG

The HADES RV Programme with HARPS-N at TNG

A Search for Additional Bodies in the GJ 1132 Planetary System from 21 Ground-based Transits and a 100-hr Spitzer Campaign

Stellar parameters of early-M dwarfs from ratios of spectral features at optical wavelengths

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