Search

We report the discovery of a super-Earth orbiting at the inner edge of the habitable zone of the star GJ 625 based on the analysis of the radial-velocity (RV) time series from the HARPS-N spectrograph, consisting in 151 HARPS-N measurements taken over 3.5 yr. GJ 625 b is a planet with a minimum mass M sin $i$ of 2.82 $\pm$ 0.51 M$_{\oplus}$ with an orbital period of 14.628 $\pm$ 0.013 days at a distance of 0.078 AU of its parent star. The host star is the quiet M2 V star GJ 625, located at 6.5 pc from the Sun. We find the presence of a second radial velocity signal in the range 74-85 days that we relate to stellar rotation after analysing the time series of Ca II H\&K and H${\alpha}$ spectroscopic indicators, the variations of the FWHM of the CCF and and the APT2 photometric light curves. We find no evidence linking the short period radial velocity signal to any activity proxy., Comment: 22 pages, 21 figures, 10 tables -- Metadata corrected

One of the main scientific drivers for ESPRESSO,\'Echelle SPectrograph, is the detection and characterization of Earth-class exoplanets. With this goal in mind, the ESPRESSO Guaranteed Time Observations (GTO) Catalog identifies the best target stars for a blind search for the radial velocity (RV) signals caused by Earth-class exoplanets. Using the most complete stellar catalogs available, we screened for the most suitable G, K, and M dwarf stars for the detection of Earth-class exoplanets with ESPRESSO. For most of the stars, we then gathered high-resolution spectra from new observations or from archival data. We used these spectra to spectroscopically investigate the existence of any stellar binaries, both bound or background stars. We derived the activity level using chromospheric activity indexes using $log(R'_{HK})$, as well as the projected rotational velocity $\textit{v sin i}$. For the cases where planet companions are already known, we also looked at the possibility that additional planets may exist in the host's habitable zone using dynamical arguments. We estimated the spectroscopic contamination level, $\textit{v sin i}$, activity, stellar parameters and chemical abundances for 249 of the most promising targets. Using these data, we selected 45 stars that match our criteria for detectability of a planet like Earth. The stars presented and discussed in this paper constitute the ESPRESSO GTO catalog for the RV blind search for Earth-class planets. They can also be used for any other work requiring a detailed spectroscopic characterization of stars in the solar neighborhood., Comment: Corrected a typo in references. Corrected typo in table B.2

International audience; Context. Since 1998, a planet-search around main sequence stars within 50 pc in the southern hemisphere has been underway with the CORALIE spectrograph at La Silla Observatory. Aims: With an observing time span of more than 20 yr, the CORALIE survey is able to detect long-term trends in data with masses and separations large enough to select ideal targets for direct imaging. Detecting these giant companion candidates will allow us to start bridging the gap between radial-velocity-detected exoplanets and directly imaged planets and brown dwarfs. Methods: Long-term precise Doppler measurements with the CORALIE spectrograph reveal radial-velocity signatures of massive planetary companions and brown dwarfs on long-period orbits. Results: In this paper, we report the discovery of new companions orbiting HD 181234, HD 13724, HD 25015, HD 92987 and HD 50499. We also report updated orbital parameters for HD 50499b, HD 92788b and HD 98649b. In addition, we confirm the recent detection of HD 92788c. The newly reported companions span a period range of 15.6-40.4 yr and a mass domain of 2.93-26.77 MJup, the latter of which straddles the nominal boundary between planets and brown dwarfs. Conclusions: We report the detection of five new companions and updated parameters of four known extrasolar planets. We identify at least some of these companions to be promising candidates for imaging and further characterisation. The radial velocity measurements and additional data products discussed in this paper are available on the DACE web platform at https://dace.unige.ch/radialVelocities. See the appendix for a direct link to the individual target data products. A copy of the data 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/625/A71Based on observations collected with the CORALIE spectrograph mounted on the 1.2 m Swiss telescope at La Silla Observatory and with the HARPS spectrograph on the ESO 3.6 m telescope at La Silla (ESO, Chile).

Aims. We extend the relationship between X-ray luminosity (Lx) and rotation period (Prot) found for main-sequence FGK stars, and test whether it also holds for early M dwarfs, especially in the non-saturated regime (Lx ∝ Prot−2) which corresponds to slow rotators. Methods. We use the luminosity coronal activity indicator (Lx) of a sample of 78 early M dwarfs with masses in the range from 0.3 to 0.75 M⊙ from the HArps-N red Dwarf Exoplanet Survey (HADES) radial velocity (RV) programme collected from ROSAT and XMM-Newton. The determination of the rotation periods (Prot) was done by analysing time series of high-resolution spectroscopy of the Ca II H & K and Hα activity indicators. Our sample principally covers the slow rotation regime with rotation periods from 15 to 60 days. Results. Our work extends to the low mass regime the observed trend for more massive stars showing a continuous shift of the Lx∕Lbol versus Prot power law towards longer rotation period values, and includes a more accurate way to determine the value of the rotation period at which the saturation occurs (Psat) for M dwarf stars. Conclusions. We conclude that the relations between coronal activity and stellar rotation for FGK stars also hold for early M dwarfs in the non-saturated regime, indicating that the rotation period is sufficient to determine the ratio Lx∕Lbol.

(Abridged) Understanding stellar activity in M dwarfs is crucial for the physics of stellar atmospheres as well as 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. We aim to test whether the relations between activity, rotation, and stellar parameters and flux-flux relationships also hold for early-M dwarfs on the main-sequence. We analyse in an 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 Halpha up to Hepsilon are obtained by using the spectral subtraction technique. The relationships between the emission excesses and the stellar parameters are studied. Relations between pairs of fluxes of different chromospheric lines are also studied. 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. 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. 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. 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., Accepted for publication by Astronomy & Astrophysics, This version: some typos corrected

We report on the installation of a laser frequency comb (LFC) at the HARPS spectrograph, which we characterize relative to a second LFC that we had brought to HARPS for testing. This allowed us for the first time to probe the relative stability of two independent astronomical LFCs over an extended wavelength range. Both LFCs covered the spectral range of HARPS at least from 460 to 690 nm. After optimization of the fiber coupling to HARPS to suppress modal noise, a relative stability of the two LFCs in the low cm/s range was obtained. In combination with the results of our four earlier LFC test campaigns on HARPS, the available data now cover a time span of more than six years.

Aims: Several studies suggest that the activity level of a planet-host star can be influenced by the presence of a close-by orbiting planet. Moreover, the interaction mechanisms that have been proposed, magnetic interaction and tidal interaction, exhibit a very different dependence on orbital separation between the star and the planet. A detection of activity enhancement and characterization of its dependence on planetary orbital distance can, in principle, allow us to characterize the physical mechanism behind the activity enhancement. Methods: We used the HARPS-N spectrograph to measure the stellar activity level of HD 80606 during the planetary periastron passage and compared the activity measured to that close to apastron. Being characterized by an eccentricity of 0.93 and an orbital period of 111 days, the system's extreme variation in orbital separation makes it a perfect target to test our hypothesis. Results: We find no evidence for a variation in the activity level of the star as a function of planetary orbital distance, as measured by all activity indicators employed log($R'_{HK}$), H$_\alpha$, NaI, and HeI. None of the models employed, whether magnetic interaction or tidal interaction, provides a good description of the data. Conclusions: We find no evidence for star-planet interaction in HD\,80606 at the moment of the periastron passage of its very eccentric planet. The straightforward explanation for the non-detection is the absence of interaction as a result of a low magnetic field strength on either the planet or the star and of the low level of tidal interaction between the two. However, we cannot exclude two scenarios: i) the interaction can be instantaneous and of magnetic origin, being concentrated on the substellar point and its surrounding area, and ii) the interaction can lead to a delayed activity enhancement. (abridged), Comment: 9 pages, 4 figures, accepted for publication in Astronomy & Astrophysics

Context. M dwarfs are considered ideal targets for Doppler radial velocity searches. Nonetheless, the statistics of frequency of low-mass planets hosted by low mass stars remains poorly constrained. Aims. Our M-dwarf radial velocity monitoring with HARPS-N can provide a major contribution to the widening of the current statistics through the in-depth analysis of accurate radial velocity observations in a narrow range of spectral sub-types (79 stars, between dM0 to dM3). Spectral accuracy will enable us to reach the precision needed to detect small planets with a few earth masses. Our survey will bring a contribute to the surveys devoted to the search for planets around M-dwarfs, mainly focused on the M-dwarf population of the northern emisphere, for which we will provide an estimate of the planet occurence. Methods. We present here a long duration radial velocity monitoring of the M1 dwarf star GJ 3998 with HARPS-N to identify periodic signals in the data. Almost simultaneous photometric observations were carried out within the APACHE and EXORAP programs to characterize the stellar activity and to distinguish from the periodic signals those due to activity and to the presence of planetary companions. Results. The radial velocities have a dispersion in excess of their internal errors due to at least four superimposed signals, with periods of 30.7, 13.7, 42.5 and 2.65 days. The analysis of spectral indices based on Ca II H & K and Halpha lines demonstrates that the periods of 30.7 and 42.5 days are due to chromospheric inhomogeneities modulated by stellar rotation and differential rotation. The shorter periods of 13.74 +/- 0.02 d and 2.6498 +/- 0.0008 d are well explained with the presence of two planets, with minimum masses of 6.26 +/- 0.79 MEarth and 2.47 +/- 0.27 MEarth and distances of 0.089 AU and 0.029 AU from the host, respectively., 19 pages, 14 figures. Accepted for publication in Astronomy & Astrophysics

We investigate the photometric modulation induced by magnetic activity cycles and study the relationship between rotation period and activity cycle(s) in late-type (FGKM) stars. We analyse light-curves spanning up to 9 years of 125 nearby stars provided by the ASAS survey. The sample is mainly conformed by low-activity main sequence late A to mid M-type stars. A search is performed for short (days) and long-term (years) periodic variations in the photometry. We modelled with combinations of sinusoids the light-curves to measure the properties of these periodic signals. To provide a better statistical interpretation of our results we complement them with the results from previous similar works. We have been able to measure long-term photometric cycles of 47 stars. Rotational modulation was also detected and rotational periods measured in 36 stars. For 28 stars we have simultaneous measurements of both, activity cycles and rotational periods, being 17 of them M-type stars. From sinusoidal fits we measured both photometric amplitudes and periods. The measured cycle periods range from 2 up to 14 yr with photometric amplitudes in the range of 5-20 mmag. We have found that the distribution of cycle lengths for the different spectral types is similar. On the other hand the distribution of rotation periods is completely different, trending to longer periods for later type stars. The amplitudes induced by magnetic cycles and rotation show a clear correlation. A trend of photometric amplitudes with rotation period is also outlined in the data. For a given activity index the amplitudes of the photometric variability induced by activity cycles of main sequence GK stars are lower than those of early and mid-M dwarfs. Using spectroscopic data we also provide an update in the empirical relationship between the level of chromospheric activity as given by log(Rhk) and the rotation periods., 14 pages, 22 figures, 5 tables

Context. Many efforts are currently made to detect Earth-like planets around low-mass stars in almost every extra-solar planet search. M dwarfs are considered ideal targets for Doppler radial velocity searches because their low masses and luminosities make low-mass planets orbiting in these stars' habitable zones more easily detectable than those around higher mass stars. Nonetheless, the frequency statistics of low-mass planets hosted by low-mass stars remains poorly constrained. Aims: Our M-dwarf radial velocity monitoring with HARPS-N within the collaboration between the Global architectures of Planetary Systems (GAPS) project, the Institut de Ciències de l'Espai/CSIC-IEEC (ICE) and the Instituto de Astrofísica de Canarias (IAC) can provide a major contribution to the widening of the current statistics through the in-depth analysis of accurate radial velocity observations in a narrow range of spectral sub-types (79 stars, between dM0 to dM3). Spectral accuracy will enable us to reach the precision needed to detect small planets with a few Earth masses. Our survey will contribute to the surveys devoted to the search for planets around M-dwarfs, mainly focused on the M-dwarf population of the northern emisphere, for which we will provide an estimate of the planet occurrence. Methods: We present here a long-duration radial velocity monitoring of the M1 dwarf star GJ 3998 with HARPS-N to identify periodic signals in the data. Almost simultaneous photometric observations were carried out within the APACHE and EXORAP programs to characterize the stellar activity and to distinguish those due to activity and to the presence of planetary companions from the periodic signals. We ran a Markov chain Monte Carlo simulation and used a Bayesian model selection to determine the number of planets in this system, to estimate their orbital parameters and minimum mass, and to properly treat the activity noise. Results: The radial velocities have a dispersion in excess of their internal errors due to at least four superimposed signals with periods of 30.7, 13.7, 42.5, and 2.65 days. Our data are well described by a two-planet Keplerian (13.7 d and 2.65 d) and a fit with two sinusoidal functions (stellar activity, 30.7 d and 42.5 d). The analysis of spectral indexes based on Ca II H & K and Hα lines demonstrates that the periods of 30.7 and 42.5 days are due to chromospheric inhomogeneities modulated by stellar rotation and differential rotation. This result is supported by photometry and is consistent with the results on differential rotation of M stars obtained with Kepler. The shorter periods of 13.74 ± 0.02 d and 2.6498 ± 0.0008 d are well explained with the presence of two planets, with masses of at least 6.26_(-0.76)^(+0.79) M⊕ and 2.47 ± 0.27 M⊕ and distances of 0.089 AU and 0.029 AU from the host, respectively. -- Based on: observations made with the Italian Telescopio Nazionale Galileo (TNG), operated on the island of La Palma by the INAF - Fundación Galileo Galilei at the Roche de Los Muchachos Observatory of the Instituto de Astrofísica de Canarias (IAC); photometric observations made with the APACHE array located at the Astronomical Observatory of the Aosta Valley; photometric observations made with the robotic telescope APT2 (within the EXORAP program) located at Serra La Nave on Mt. Etna. http://www.oact.inaf.it/exoit/EXO-IT/Projects/Entries/2011/12/27_GAPS.html

The search for exo-Earths using Doppler spectroscopy faces nowadays two main difficulties. The first is a technical limitation. The precision of the instruments limits the measurable amplitudes to signals produced by super-Earths orbiting close to their host stars. Terrestrial planets orbiting solar-type stars induce variations smaller than 1 m s−1 except when orbiting very close to the star. The arrival of ESPRESSO and the Laser Frequency Comb as calibration unit will palliate this limitation and move the measurement precision to the range of 5 cm s−1 . So far the search in solar-Type stars is limited to super-Earths. The alternative is to find terrestrial planets in the habitable zone is the search around M-type stars. Their lower mass makes the signals of terrestrial planets detectable by today’s instruments. The second issue is the presence of radial velocity variations induced by the homogeneities of the stellar surface. The changes in the stellar surface and the stellar rotation induce periodic signals that go from less than 1 m s−1 in the quietest stars to dozens of m s−1 in active stars and might be easily mistaken for signals induced by rocky planets. In the case of M-dwarfs the need of performing the analysis of the stellar induced signals is even more important. Signals produced by early M-dwarfs have periods compatible with the habitable zone of those stars and amplitudes similar to those of super-Earths. The rise in precision expected for the next years will make this kind of signals visible even in the quietest stars making even more important to understand and correctly model them. Using chromospheric indicators from high resolution spectroscopic and photometric time series we study both long term and short term variability (solarlike cycles and rotation) of a sample of 176 low magnetic activity stars with spectral types going from late F-type to mid M-type stars. We provide new measurements of magnetic cycles for 105 stars, and rotation periods for 123 stars. We study the distribution of rotation periods, finding that there is an evolution in the rotation period lengths, getting longer for later type stars, that saturates when reaching K-type stars and begins to increase again at types later than M2. We study the distribution of magnetic cycles, finding no clear difference among different spectral types. We study the relationships between the measured periods and the chromospheric activity level of the stars, measured as the log10(R0 HK). To do so we extend the log10(R0 HK) calibration to cover stars up to B-V ∼ 2.0. We find a strong correlation between the measured rotation period and the mean level of chromospheric activity that allows to predict the rotation periods of main sequence stars from G-type to mid M-type with an accuracy of the ∼ 20% of the period. We analyse the radial velocity time series of 133 stars searching both for activity induce signals and planetary signals. We detect rotation induced signals in 46 stars, with amplitudes going from 0.3 to 16.4 ms−1 . We study the relationship between the amplitude of the induced signals and the activity indicators, finding a correlation between the mean level of chromospheric activity log10(R0 HK) and the measured amplitude of the signal. This relationship shows that FGK stars show a similar behaviour, which is different for M-type stars. We find also a relationship between the amplitude of the modulation in the Mount Wilson S index and the amplitude of the induced radial velocity signal. This relationship behaves differently for two populations of stars, with a breaking point around mid-K stars. After cleaning the radial velocity series form stellar activity induced signals we performed a search for dynamical signals in the same sample of stars. We recovered most of the previously published planet candidates, except for a few cases where we attribute a stellar origin to the previously assumed planetary companion. We present the discovery of six new planets around the stars HD 1581, HD 161098, HD 176986, GJ 536 and GJ 3998, with minimum masses in M⊕ units of 5.87 ± 0.99, 26.60 ± 4.39, 4.86 ± 0.66 and 5.47 ± 0.84, 2.35 ± 0.42 and 6.12 ± 1.11 respectively located at 0.321, 2.503, 0.061, 0.066, 0.029 and 0.089 au from their parent stars. The latter two have been reported by Affer et al. (2016). Five of them are presumably rocky planets. We suggest the presence of a seventh one in the star HD 161098 with a minimum mass of 5.30 ± 1.22 M⊕ located at 0.317 au of the star, which could be habitable given the appropriate atmospheric conditions. We suggest also the presence of five additional candidates that still require further analysis and observations. La búsqueda de exotierras por medio de espectroscopía doppler se enfrenta hoy en día a dos grandes dificultades. La primera es de carácter técnico. En estrellas de tipo solar la precisión de los instrumentos existentes limita la amplitud de las señales que se pueden medir a aquellas producidas por supertierras a separaciones orbitales cercanas a sus estrellas. Los planetas de tipo terrestre orbitando alrededor de estrellas de tipo solar producen variaciones muy inferiores a 1 m/s excepto a distancias muy cercanas a la estrella. La llegada de ESPRESSO y el Laser Frequency Comb como unidad de calibración paliarán esta limitación al llevar la precisión de las medidas hasta el rango de los 5 cm/s. Hasta ese momento la búsqueda en estrellas de tipo solar queda limitada a supertierras. La alternativa en estos momentos está en la búsqueda alrededor de estrellas de tipo M, ya que su baja masa hace que las señales de los planetas de tipo terrestre sean detectables con los instrumentos actuales. La segunda dificultad está en las variaciones en velocidad radial producidas por las inhomogeneidades de la superficie de las estrellas. Los cambios en las regiones activas de la superficie en las estrellas y su rotación provocan variaciones periódicas en la velocidad radial que pueden ir desde menos de 1 m/s en estrellas tranquilas hasta varias decenas de m/s en las más activas y pueden ser fácilmente confundidas con la variación provocada por planetas rocosos. En el caso de las estrellas M la necesidad de realizar este análisis de las señales originadas por la actividad estelar resulta aun más importante. Las señales inducidas por las estrellas M tempranas tienen periodos compatibles con los de las órbitas de los planetas en la zona habitable de estas estrellas, y amplitudes compatibles con las de las supertierras. Con el aumento de precisión previsto para el futuro estas señales aparecerán hasta en las estrellas menos activas conocidas, resultando cada vez más importante entenderlas y modelarlas correctamente. Usando series temporales de indicadores cromosféricos de espectros de alta resolución y curvas fotométricas estudiamos la variabilidad de 176 estrellas de baja actividad magnética de tipos espectrales desde F tardío hasta M intermedio, buscando tanto actividad a largo plazo (ciclos similares al ciclo solar) como a corto plazo (rotación). Presentamos nuevas medidas de ciclos magnéticos para 105 estrellas, y periodos de rotación para 123 estrellas. Estudiamos la distribución de periodos de rotación, donde encontramos una evolución hacia mayores valores en la duración del periodo en los tipos espectrales más tardíos. Esa evolución se detiene al llegar a las estrellas de tipo K temprano, y se reanuda al cruzar la frontera de las estrellas M2. Estudiamos así mismo la distribución de ciclos magnéticos, sin encontrar diferencias evidentes entre las estrellas de diferentes tipos espectrales. Estudiamos la relación entre el periodo de rotación medido y el nivel medio de actividad cromosférica, medido como el log(Rhk). Para ello extendemos la calibración del log(Rhk) para cubrir estrellas de B-V hasta ~2.0. Encontramos una fuerte correlación entre el periodo de rotación medido y el nivel de actividad cromosférica, que permite predecir el periodo de rotación de estrellas desde estrellas de tipo G hasta estrellas de tipo M intermedio de secuencia principal con una precisión del ~23\%. Analizamos las curvas de velocidad radial de 133 estrellas buscando tanto señales de velocidad radial inducidas por actividad como señales inducidas por planetas. Detectamos la señal inducida por rotación en 46 estrellas, con amplitudes desde 0.3 hasta 16.4 m/s. Estudiamos la relación entre la amplitud de las señales inducidas y los indicadores de actividad cromosférica, encontrando una vez más una correlación entre el nivel medio de actividad log(Rhk) y la amplitud de la señal inducida. Esta relación nos enseña que las estrellas FGK siguen un comportamiento similar, mientras que para las estrellas M las amplitudes inducidas son mayores. Encontramos también una relación entre la amplitud de la modulación rotacional del índice Smw y la amplitud de la señal en velocidad radial inducida por la rotación. En este caso encontramos dos poblaciones bien diferenciadas, divididas por las estrellas de tipo K intermedio. Tras limpiar las curvas de velocidad radial de señales inducidas por actividad llevamos a cabo una búsqueda de señales dinámicas en la misma muestra de estrellas. Recuperamos la mayor parte de los candidatos a planetas previamente publicados, salvo unos pocos casos donde atribuimos a la señal un origen intrínseco a la estrella. Presentamos el descubrimiento de seis nuevos planetas alrededor de las estrellas HD 1581, HD 161098, HD 176986, GJ 536 y GJ 3998, con masas mínimas de 5.87 +- 0.99, 26.60 +- 4.39, 4.86 +- 0.66 y 5.47 +- 0.84 Me, 2.35 +- 0.42 Me y 6.12 +- 1.11 Me respectivamente, situados a 0.321, 2.503, 0.061, 0.066, 0.029 y 0.089 au de sus estrellas. Los dos últimos publicados ya por Affer et al. 2016. Cinco de ellos probablemente sean planetas rocosos. Sugerimos también la presencia de un séptimo en la estrella HD 161098 con una masa mínima de 5.30 +-1.22 Me orbitando a una distancia de 0.317 au, que podría ser habitable si se diesen las condiciones atmosféricas apropiadas. Sugerimos por último la presencia de otros cinco candidatos que aún requieren observaciones adicionales y un análisis detallado.

We aim to investigate the presence of signatures of magnetic cycles and rotation on a sample of 71 early M-dwarfs from the HADES RV programme using high-resolution time-series spectroscopy of the Ca II H & K and Halpha chromospheric activity indicators, the radial velocity series, the parameters of the cross correlation function and the V-band photometry. We used mainly HARPS-N spectra, acquired over four years, and add HARPS spectra from the public ESO database and ASAS photometry light-curves as support data, extending the baseline of the observations of some stars up to 12 years. We provide log(R'hk) measurements for all the stars in the sample, cycle length measurements for 13 stars, rotation periods for 33 stars and we are able to measure the semi-amplitude of the radial velocity signal induced by rotation in 16 stars. We complement our work with previous results and confirm and refine the previously reported relationships between the mean level of chromospheric emission, measured by the log(R'hk), with the rotation period, and with the measured semi-amplitude of the activity induced radial velocity signal for early M-dwarfs. We searched for a possible relation between the measured rotation periods and the lengths of the magnetic cycle, finding a weak correlation between both quantities. Using previous v sin i measurements we estimated the inclinations of the star's poles to the line of sight for all the stars in the sample, and estimate the range of masses of the planets GJ 3998 b and c (2.5 - 4.9 Mearth and 6.3 - 12.5 Mearth), GJ 625 b (2.82 Mearth), GJ 3942 b (7.1 - 10.0 Mearth) and GJ 15A b (3.1 - 3.3 Mearth), assuming their orbits are coplanar with the stellar rotation., 19 pages, 16 figures, 10 tables

We determine rotation periods of a sample of 48 late F-type to mid-M dwarf stars using time-series high-resolution spectroscopy of the Ca II H&K and H-alpha chromospheric activity indicators. We find good agreement between the rotation periods obtained from each of these two indicators. An empirical relationship between the level of chromospheric emission measured by log (R'HK) and the spectroscopic rotation periods is reported. This relation is largely independent of the spectral type and the metallicity of the stars and can be used to make a reliable prediction of rotation periods for late K to mid-M dwarfs with low levels of activity. For some stars in the sample, the measured spectroscopic rotation periods coincide, or are very close, to the orbital periods of postulated planets. In such cases, further studies are needed to clarify whether the associated periodic radial velocity signals reveal the existence of planets or are due to magnetic activity., 13 pages, 13 figures, 5 tables

We report the discovery of a super-Earth orbiting the star GJ 536 based on the analysis of the radial-velocity time series from the HARPS and HARPS-N spectrographs. GJ 536 b is a planet with a minimum mass M sin $i$ of 5.36 +- 0.69 Me with an orbital period of 8.7076 +- 0.0025 days at a distance of 0.066610(13) AU, and an orbit that is consistent with circular. The host star is the moderately quiet M1 V star GJ 536, located at 10 pc from the Sun. We find the presence of a second signal at 43 days that we relate to stellar rotation after analysing the time series of Ca II H&K and H alpha spectroscopic indicators and photometric data from the ASAS archive. We find no evidence linking the short period signal to any activity proxy. We also tentatively derived a stellar magnetic cycle of less than 3 years., 14 pages, 14 figures, 5 tables, Accepted in A&A

We aim at constraining evolutionary models at low mass and young ages by identifying interesting transiting system members of the nearest OB association to the Sun, Upper Scorpius, targeted by the Kepler mission. We produced light curves for M dwarf members of the USco region surveyed during the second campaign of the Kepler K2 mission. We identified 'by eye' a transiting system, UScoJ161630.68-251220.1 (=EPIC203710387) with a combined spectral type of M5.25 whose photometric, astrometric, and spectroscopic properties makes it a member of USco. We conducted an extensive photometric and spectroscopic follow-up of this transiting system with a suite of telescopes and instruments to characterise the properties of each component of the system. We calculated a transit duration of about 2.42 hours occuring every 2.88 days with a slight difference in transit depth and phase between the two components. We estimated a mass ratio of 0.922+/-0.015 from the semi-amplitudes of the radial velocity curves for each component. We derived masses of 0.091+/-0.005 Msun and 0.084+/-0.004 Msun,radii of 0.388+/-0.008 Rsun and 0.380+/-0.008 Rsun, luminosities of log(L/Lsun)=-2.020 (-0.121+0.099) dex and -2.032 (-0.121+0.099) dex, and effective temperatures of 2901 (-172+199) K and 2908 (-172+199) K for the primary and secondary, respectively. We present a complete photometric and radial velocity characterisation of the least massive double-line eclipsing binary system in the young USco association with two components close to the stellar/substellar limit. This system fills in a gap between the least massive eclipsing binaries in the low-mass and substellar regimes at young ages and represents an important addition to constrain evolutionary models at young ages., 15 pages, 12 figures, 5 tables, accepted for publication to A&A

(Abridged) Low-mass stars have been recognised as promising targets in the search for rocky, small planets with the potential of supporting life. Doppler search programmes using high-resolution spectrographs like HARPS or HARPS-N are providing huge quantities of optical spectra of M dwarfs. We aim to calibrate empirical relationships to determine stellar parameters for early M dwarfs (spectral types M0-M4.5) using the same spectra that are used for the radial velocity determinations. Our methodology consists in the use of ratios of pseudo equivalent widths of spectral features as a temperature diagnostic. 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 being observed in the framework of the HARPS 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. A total of 112 temperature sensitive ratios have been calibrated over the range 3100-3950 K, providing Teff values with typical uncertainties of the order of 70 K. Eighty-two ratios of pseudo equivalent widths of features were calibrated to derive spectral types. Regarding stellar metallicity, 696 combinations of pseudo equivalent widths of individual features and temperature-sensitive ratios have been calibrated, over the 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., Accepted for publication by Astronomy and Astrophysics

Ehrenreich, D.et al., Ultrahot giant exoplanets receive thousands of times Earth’s insolation. Their high-temperature atmospheres (greater than 2,000 kelvin) are ideal laboratories for studying extreme planetary climates and chemistry. Daysides are predicted to be cloud-free, dominated by atomic species and much hotter than nightsides. Atoms are expected to recombine into molecules over the nightside, resulting in different day and night chemistries. Although metallic elements and a large temperature contrast have been observed, no chemical gradient has been measured across the surface of such an exoplanet. Different atmospheric chemistry between the day-to-night (‘evening’) and night-to-day (‘morning’) terminators could, however, be revealed as an asymmetric absorption signature during transit. Here we report the detection of an asymmetric atmospheric signature in the ultrahot exoplanet WASP-76b. We spectrally and temporally resolve this signature using a combination of high-dispersion spectroscopy with a large photon-collecting area. The absorption signal, attributed to neutral iron, is blueshifted by −11 ± 0.7 kilometres per second on the trailing limb, which can be explained by a combination of planetary rotation and wind blowing from the hot dayside. In contrast, no signal arises from the nightside close to the morning terminator, showing that atomic iron is not absorbing starlight there. We conclude that iron must therefore condense during its journey across the nightside., With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737)

This paper reports on the detailed characterisation of the K2-111 planetary system with K2, WASP, and ASAS-SN photometry as well as high-resolution spectroscopic data from HARPS-N and ESPRESSO. The host, K2-111, is confirmed to be a mildly evolved (logg=4.17), iron-poor ([Fe/H]=−0.46), but alpha-enhanced ([α/Fe]=0.27), chromospherically quiet, very old thick disc G2 star. A global fit, performed by using PyORBIT shows that the transiting planet, K2-111b, orbits with a period Pb=5.3518±0.0004 d, and has a planet radius of 1.82+0.11−0.09 R⊕ and a mass of 5.29+0.76−0.77 M⊕, resulting in a bulk density slightly lower than that of the Earth. The stellar chemical composition and the planet properties are consistent with K2-111b being a terrestrial planet with an iron core mass fraction lower than the Earth. We announce the existence of a second signal in the radial velocity data that we attribute to a non-transiting planet, K2-111c, with an orbital period of 15.6785±0.0064 days, orbiting in near-3:1 mean-motion resonance with the transiting planet, and a minimum planet mass of 11.3±1.1 M⊕. Both planet signals are independently detected in the HARPS-N and ESPRESSO data when fitted separately. There are potentially more planets in this resonant system, but more well-sampled data are required to confirm their presence and physical parameters.

The bright star π Men was chosen as the first target for a radial velocity follow-up to test the performance of ESPRESSO, the new high-resolution spectrograph at the ESO's Very-Large Telescope (VLT). The star hosts a multi-planet system (a transiting 4 M⊕ planet at ∼0.07 au, and a sub-stellar companion on a ∼2100-day eccentric orbit) which is particularly appealing for a precise multi-technique characterization. With the new ESPRESSO observations, that cover a time span of 200 days, we aim to improve the precision and accuracy of the planet parameters and search for additional low-mass companions. We also take advantage of new photometric transits of π Men c observed by TESS over a time span that overlaps with that of the ESPRESSO follow-up campaign. We analyse the enlarged spectroscopic and photometric datasets and compare the results to those in the literature. We further characterize the system by means of absolute astrometry with Hipparcos and Gaia. We used the spectra of ESPRESSO for an independent determination of the stellar fundamental parameters. We present a precise characterization of the planetary system around π Men. The ESPRESSO radial velocities alone (with typical uncertainty of 10 cm/s) allow for a precise retrieval of the Doppler signal induced by π Men c. The residuals show an RMS of 1.2 m/s, and we can exclude companions with a minimum mass less than ∼2 M⊕ within the orbit of π Men c). We improve the ephemeris of π Men c using 18 additional TESS transits, and in combination with the astrometric measurements, we determine the inclination of the orbital plane of π Men b with high precision (ib=45.8+1.4−1.1 deg). This leads to the precise measurement of its absolute mass mb=14.1+0.5−0.4 MJup, and shows that the planetary orbital planes are highly misaligned.

The detection and characterization of exoplanet atmospheres is currently one of the main drivers pushing the development of new observing facilities. In this context, high-resolution spectrographs are {proving} their potential and showing that high-resolution spectroscopy will be paramount in this field. We aim to make use of ESPRESSO high-resolution spectra, which cover two transits of HD209458b, to probe the broadband transmission optical spectrum of the planet. We applied the chromatic Rossiter-McLaughin method to derive the transmission spectrum of HD209458b. We compared the results with previous HST observations and with synthetic spectra. We recover a transmission spectrum of HD209458b similar to the one obtained with HST data. The models suggest that the observed signal can be explained by only Na, only TiO, or both Na and TiO, even though none is fully capable of explaining our observed transmission spectrum. Extra absorbers may be needed to explain the full dataset, though modeling approximations and observational errors can also be responsible for the observed mismatch. Using the chromatic Rossiter-McLaughlin technique, ESPRESSO is able to provide broadband transmission spectra of exoplanets from the ground, in conjunction with space-based facilities, opening good perspectives for similar studies of other planets.

This paper reports on the detailed characterisation of the K2-111 planetary system with K2, WASP, and ASAS-SN photometry as well as high-resolution spectroscopic data from HARPS-N and ESPRESSO. The host, K2-111, is confirmed to be a mildly evolved ($\log g=4.17$), iron-poor ([Fe/H]$=-0.46$), but alpha-enhanced ([$\alpha$/Fe]$=0.27$), chromospherically quiet, very old thick disc G2 star. A global fit, performed by using PyORBIT shows that the transiting planet, K2-111b, orbits with a period $P_b=5.3518\pm0.0004$ d, and has a planet radius of $1.82^{+0.11}_{-0.09}$ R$_\oplus$ and a mass of $5.29^{+0.76}_{-0.77}$ M$_\oplus$, resulting in a bulk density slightly lower than that of the Earth. The stellar chemical composition and the planet properties are consistent with K2-111b being a terrestrial planet with an iron core mass fraction lower than the Earth. We announce the existence of a second signal in the radial velocity data that we attribute to a non-transiting planet, K2-111c, with an orbital period of $15.6785\pm 0.0064$ days, orbiting in near-3:1 mean-motion resonance with the transiting planet, and a minimum planet mass of $11.3\pm1.1$ M$_\oplus$. Both planet signals are independently detected in the HARPS-N and ESPRESSO data when fitted separately. There are potentially more planets in this resonant system, but more well-sampled data are required to confirm their presence and physical parameters.

Esta disertación se centra en investigar la transformación que ha sufrido la narrativa de los videojuegos en los últimos treinta años y su relación con el entorno de juego y la experiencia del jugador. Tomando como objeto de estudio la saga Final Fantasy que ha cumplido treinta años el 18 de diciembre de 2017. Aquesta dissertació se centra en investigar la transformació que ha sofert la narrativa dels videojocs en els últims trenta anys i la seva relació amb l'entorn de joc i l'experiència del jugador. Prenent com a objecte d'estudi la saga Final Fantasy que ha complert trenta anys el 18 de desembre de 2017. The dissertation focuses on the investigation about the changes in the narrative of video games during the last thirty years, regarding the game environment and the player's experience. We will take Final Fantasy as a case study as it has reached thirty years of age as of December 18th 2017.

We report the discovery of a system of two super-Earths orbiting the moderately active K-dwarf HD 176986. This work is part of the RoPES RV program of G- and K-type stars, which combines radial velocities (RVs) from the HARPS and HARPS-N spectrographs to search for short-period terrestrial planets. HD 176986 b and c are super-Earth planets with masses of 5.74 and 9.18 M$_{\oplus}$, orbital periods of 6.49 and 16.82 days, and distances of 0.063 and 0.119 AU in orbits that are consistent with circular. The host star is a K2.5 dwarf, and despite its modest level of chromospheric activity (log(R'hk) = - 4.90 +- 0.04), it shows a complex activity pattern. Along with the discovery of the planets, we study the magnetic cycle and rotation of the star. HD 176986 proves to be suitable for testing the available RV analysis technique and further our understanding of stellar activity., Comment: 21 pages, 24 figures, 7 tables

The study of exoplanet atmospheres is essential to understand the formation, evolution and composition of exoplanets. The transmission spectroscopy technique is playing a significant role in this domain. In particular, the combination of state-of-the-art spectrographs at low- and high-spectral resolution is key to our understanding of atmospheric structure and composition. Two transits of the close-in sub Saturn-mass planet,WASP-127b, have been observed with ESPRESSO in the frame of the Guaranteed Time Observations Consortium. Transit observations allow us to study simultaneously the system architecture and the exoplanet atmosphere. We found that this planet is orbiting its slowly rotating host star (veq sin(i)=0.53+/-0.07 km/s) on a retrograde misaligned orbit (lambda=-128.41+/-5.60 deg). We detected the sodium line core at the 9-sigma confidence level with an excess absorption of 0.3+/-0.04%, a blueshift of 2.7+/-0.79 km/s and a FWHM of 15.18+/-1.75 km/s. However, we did not detect the presence of other atomic species but set upper-limits of only few scale heights. Finally, we put a 3-sigma upper limit, to the average depth of the 1600 strongest water lines at equilibrium temperature in the visible band, of 38 ppm. This constrains the cloud-deck pressure between 0.3 and 0.5 mbar by combining our data with low-resolution data in the near-infrared and models computed for this planet. To conclude, WASP-127b, with an age of about 10 Gyr, is an unexpected exoplanet by its orbital architecture but also by the small extension of its sodium atmosphere (~7 scale heights). ESPRESSO allows us to take a step forward in the detection of weak signals, thus bringing strong constraints on the presence of clouds in exoplanet atmospheres. The framework proposed in this work can be applied to search for molecular species and study cloud-decks in other exoplanets.