Search

Detections of molecules in the atmosphere of gas giant exoplanets allow us to investigate the physico-chemical properties of the atmospheres. Their inferred chemical composition is used as tracer of planet formation and evolution mechanisms. Currently, an increasing number of detections is showing a possible rich chemistry of the hotter gaseous planets, but whether this extends to cooler giants is still unknown. We observed four transits of WASP-80 b, a warm transiting giant planet orbiting a late-K dwarf star with the near-infrared GIANO-B spectrograph installed at the Telescopio Nazionale Galileo and performed high resolution transmission spectroscopy analysis. We report the detection of several molecular species in its atmosphere. Combining the four nights and comparing our transmission spectrum to planetary atmosphere models containing the signature of individual molecules within the cross-correlation framework, we find the presence of H2O, CH4, NH3 and HCN with high significance, tentative detection of CO2, and inconclusive results for C2H2 and CO. A qualitative interpretation of these results, using physically motivated models, suggests an atmosphere consistent with solar composition and the presence of disequilibrium chemistry and we therefore recommend the inclusion of the latter in future modelling of sub-1000K planets., Comment: 12 pages, 4 figures. AJ, Accepted July 11th, 2022

Ariel, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, was adopted as the fourth medium-class mission in ESA's Cosmic Vision programme to be launched in 2029. During its 4-year mission, Ariel will study what exoplanets are made of, how they formed and how they evolve, by surveying a diverse sample of about 1000 extrasolar planets, simultaneously in visible and infrared wavelengths. It is the first mission dedicated to measuring the chemical composition and thermal structures of hundreds of transiting exoplanets, enabling planetary science far beyond the boundaries of the Solar System. The payload consists of an off-axis Cassegrain telescope (primary mirror 1100 mm x 730 mm ellipse) and two separate instruments (FGS and AIRS) covering simultaneously 0.5-7.8 micron spectral range. The satellite is best placed into an L2 orbit to maximise the thermal stability and the field of regard. The payload module is passively cooled via a series of V-Groove radiators; the detectors for the AIRS are the only items that require active cooling via an active Ne JT cooler. The Ariel payload is developed by a consortium of more than 50 institutes from 16 ESA countries, which include the UK, France, Italy, Belgium, Poland, Spain, Austria, Denmark, Ireland, Portugal, Czech Republic, Hungary, the Netherlands, Sweden, Norway, Estonia, and a NASA contribution., Comment: Ariel Definition Study Report, 147 pages. Reviewed by ESA Science Advisory Structure in November 2020. Original document available at: https://www.cosmos.esa.int/documents/1783156/3267291/Ariel_RedBook_Nov2020.pdf/

The dispersal of protoplanetary disks sets the timescale available for planets to assemble, and thus it is one of the fundamental parameters in theories of planetary formation. Disk dispersal is determined by several properties of the central star, the disk itself, and the surrounding environment. In particular, the metallicity of disks may impact their evolution, even if to date controversial results exist: in low-metallicity clusters disks seem to rapidly disperse, while in the Magellanic Clouds some evidence supports the existence of accreting disks few tens of Myrs old. In this paper we study the dispersal timescale of disks in Dolidze~25, the young cluster in proximity of the Sun with lowest metallicity, with the aim of understanding whether disk evolution is impacted by the low-metallicity of the cluster. We have analyzed Chandra/ACIS-I observations of the cluster and combined the resulting source catalog with existing optical and infrared catalogs of the region. We selected the disk-bearing population and the disk-less population of Dolidze 25. We have derived stellar parameters from isochrones fitted to color-magnitude diagrams. We derived a disk fraction of about 34% and a median age of 1.2 Myrs. By comparing this estimate with existing estimates of the disk fraction of clusters younger than 10 Myrs, our study suggests that the disk fraction of Dolidze 25 is lower than what is expected from its age alone. Even if our results are not conclusive given the intrinsic uncertainty on stellar ages estimated from isochrones fitting to color-magnitude diagrams, we suggest that disk evolution in Dolidze 25 may be impacted by the environment. Given the poor O star population and low stellar density of the cluster, it is more likely that disks dispersal timescale is dictated more by the low metallicity of the cluster rather than external photoevaporation or dynamical encounters., Accepted for publication by Astronomy & Astrophysics

The evolution of young stars and disks is driven by the interplay of several processes, notably accretion and ejection of material. Critical to correctly describe the conditions of planet formation, these processes are best probed spectroscopically. About five-hundred orbits of the Hubble Space Telescope (HST) are being devoted in 2020-2022 to the ULLYSES public survey of about 70 low-mass (M, Comment: Accepted for publication on Astronomy & Astrophysics. 15 pages + appendix, language edited version

Since 2012 the GAPS (Global Architecture of Planetary Systems) project at the Telescopio Nazionale Galileo (TNG) involves a large part of the Italian community working on exoplanetary science. In the first five years, the project was based on radial velocity (RV) surveys with the HARPS-N@TNG spectrograph and was focused on the search and characterization of planetary systems around stars with different properties. In 2017, thanks to the integration of GIARPS (GIANO-B & HARPS-N) at the TNG, the GAPS2 project started to explore the origin and the diversity of planetary systems adopting a twofold approach: the observation of planetary atmospheres and the detection/study of planets around young stars. The current literature suggests that we should expect a large fraction of hot Jupiters around very young stars with respect to the old ones, but the available statistic is poor and based on claimed detections still not confirmed by independent investigations. The observation of planets around young objects is therefore important because it allows us to study the ongoing planet formation, helping to investigate the role played by the formation sites, the migration mechanisms, and the orbit evolution.

Context. The mass accretion rate (Ṁacc) is the fundamental parameter to understand the process of mass assembly that results in the formation of a low-mass star. This parameter has been largely studied in Classical T Tauri stars in star-forming regions with ages of ∼1 − 10 Myr. However, little is known about the accretion properties of young stellar objects (YSOs) in younger regions and early stages of star formation, such as in the Class 0/I phases. Aims. We present new near-infrared spectra of 17 Class I/Flat and 35 Class II sources located in the young (< 1 Myr) NGC 1333 cluster, acquired with the KMOS instrument at the Very Large Telescope. Our goal is to study whether the mass accretion rate evolves with age, as suggested by the widely adopted viscous evolution model, by comparing the properties of the NGC 1333 members with samples of older regions. Methods. For the Class II sources in our sample, we measured the stellar parameters (SpT, AV, and L⋆) through a comparison of the IR spectra with a grid of non-accreting Class III stellar templates. We then computed the accretion luminosity by using the known correlation between Lacc and the luminosity of HI lines (Paβ and Brγ). For the Class I sample, where the presence of a large IR excess makes it impossible to use the same spectral typing method, we applied a procedure that allowed us to measure the stellar and accretion luminosity in a self-consistent way. Mass accretion rates Ṁacc were then measured once masses and radii were estimated adopting suitable evolutionary tracks. Results. The NGC 1333 Class II sources of our sample have Lacc ∼ 10−4 − 1 L⊙ and Ṁacc ∼ 10−11 − 10−7 M⊙ yr−1. We find a correlation between accretion and stellar luminosity in the form of log Lacc = (1.5 ± 0.2)log L⋆ + ( − 1.0 ± 0.1), and a correlation between the mass accretion rate and stellar mass in the form of log Ṁacc = (2.6 ± 0.9) log M⋆ + (−7.3 ± 0.7). Both correlations are compatible within the errors with the older Lupus star-forming region, while only the latter is consistent with results from Chamaeleon I. The Class I sample shows larger accretion luminosities (∼10−2 − 102 L⊙) and mass accretion rates (∼10−9 − 10−6 M⊙ yr−1) with respect to the Class II stars of the same cloud. However, the derived mass accretion rates are not sufficiently high to build up the inferred stellar masses, assuming steady accretion during the Class I lifetime. This suggests that the sources are not in their main accretion phase and that most of their mass has already been accumulated during a previous stage and/or that the accretion is an episodic phenomenon. We show that some of the targets originally classified as Class I through Spitzer photometry are in fact evolved or low accreting objects. This evidence can have implications for the estimated protostellar phase lifetimes. Conclusions. The accretion rates of our sample are larger in more embedded and early stage YSOs. Further observations of larger samples in young star-forming regions are needed to determine if this is a general result. In addition, we highlight the importance of spectroscopic surveys of YSOs to confirm their classification and perform a more correct estimate of their lifetime.

Young open clusters (t, 26 pages, 14 figures, accepted for publication in A&A

The atmospheres of gaseous giant exoplanets orbiting close to their parent stars (hot Jupiters) have been probed for nearly two decades. They allow us to investigate the chemical and physical properties of planetary atmospheres under extreme irradiation conditions. Previous observations of hot Jupiters as they transit in front of their host stars have revealed the frequent presence of water vapour and carbon monoxide in their atmospheres; this has been studied in terms of scaled solar composition under the usual assumption of chemical equilibrium. Both molecules as well as hydrogen cyanide were found in the atmosphere of HD 209458b, a well studied hot Jupiter (with equilibrium temperature around 1,500 kelvin), whereas ammonia was tentatively detected there and subsequently refuted. Here we report observations of HD 209458b that indicate the presence of water (H2O), carbon monoxide (CO), hydrogen cyanide (HCN), methane (CH4), ammonia (NH3) and acetylene (C2H2), with statistical significance of 5.3 to 9.9 standard deviations per molecule. Atmospheric models in radiative and chemical equilibrium that account for the detected species indicate a carbon-rich chemistry with a carbon-to-oxygen ratio close to or greater than 1, higher than the solar value (0.55). According to existing models relating the atmospheric chemistry to planet formation and migration scenarios, this would suggest that HD 209458b formed far from its present location and subsequently migrated inwards. Other hot Jupiters may also show a richer chemistry than has been previously found, which would bring into question the frequently made assumption that they have solar-like and oxygen-rich compositions., Comment: As part of the Springer Nature Content Sharing Initiative, it is possible to access a view-only version of this paper by using the following SharedIt link: https://rdcu.be/cifrz

It has recently been suggested that all giant stars with mass below 2 $M_{\odot}$ suffer an episode of surface lithium enrichment between the tip of the red giant branch (RGB) and the red clump (RC). We test if the above result can be confirmed in a sample of RC and RGB stars that are members of open clusters. We discuss Li abundances in six open clusters with ages between 1.5 and 4.9 Gyr (turn-off masses between 1.1 and 1.7 $M_{\odot}$). These observations are compared with the predictions of different models that include rotation-induced mixing, thermohaline instability, mixing induced by the first He flash, and energy losses by neutrino magnetic moment. In six clusters, we find about 35\% RC stars with Li abundances that are similar or higher than those of upper RGB stars. This can be a sign of fresh Li production. Because of the extra-mixing episode connected to the luminosity bump, the expectation was for RC stars to have systematically lower surface Li abundances. However, we cannot confirm that the possible Li production is ubiquitous. For about 65\% RC giants we can only determine abundance upper limits that could be hiding very low Li abundances. Our results indicate a possible production of Li during the RC, at levels that would not classify the stars as Li rich. Determination of their carbon isotopic ratio would help to confirm that the RC giants have suffered extra mixing followed by Li enrichment. The Li abundances of the RC stars can be qualitatively explained by the models with an additional mixing episode close to the He flash., Comment: Accepted for publication in A&A, 8 pages, 5 figures, tables available online and under request

The mass-accretion rate, Ṁacc, is a crucial parameter for the study of the evolution of accretion disks around young low-mass stellar objects (YSOs) and for planet formation studies. The Taurus star forming region (SFR) is rich in pre-main sequence stars, most of them of the T Tauri class. A variety of methodologies have been used in the past to measure mass accretion in samples of YSOs in Taurus, but despite being a general benchmark for star formation studies, a comprehensive and systematic analysis of the Taurus T Tauri population, where the stellar and accretion properties are derived homogeneously and simultaneously, is still missing. As part of the GIARPS High-resolution Observations of T Tauri stars (GHOsT) project, here we present a pilot study of the stellar and accretion properties of seven YSOs in Taurus using the spectrograph GIARPS at the Telescopio Nazionale Galileo. Contemporaneous low-resolution spectroscopic and photometric ancillary observations allow us to perform an accurate flux calibration of the high-resolution spectra. The simultaneity of the high-resolution, wide-band spectroscopic observations, from the optical to the near-infrared (NIR), the veiling measurements in such wide spectral range, and many well-calibrated emission line diagnostics allows us to derive the stellar and accretion properties of the seven YSOs in a homogeneous and self-consistent way. The procedures and methodologies presented here will be adopted in future works for the analysis of the complete GHOsT data set. We discuss the accretion properties of the seven YSOs in comparison with the 90% complete sample of YSOs in the Lupus SFR and investigate possibilities for the origin of the continuum excess emission in the NIR. Based on observations made with the GIARPS instrument at the Telescopio Nazionale Galileo under program A36TAC_22 (PI: Antoniucci).

Ariel has been selected as the next ESA M4 science mission and it is expected to be launched in 2028. During its 4-year mission, Ariel will observe the atmospheres of a large and diversified population of transiting exoplanets. A key factor for the achievement of the scientific goal of Ariel is the selection strategy for the definition of the input target list. A meaningful choice of the targets requires an accurate knowledge of the planet hosting star properties and this is necessary to be obtained well before the launch. In this work, we present the results of a bench-marking analysis between three different spectroscopic techniques used to determine stellar parameters for a selected number of targets belonging to the Ariel reference sample. We aim to consolidate a method that will be used to homogeneously determine the stellar parameters of the complete Ariel reference sample. Homogeneous, accurate and precise derivation of stellar parameters is crucial for characterizing exoplanet-host stars and in turn is a key factor for the accuracy of the planet properties., Comment: 15 pages, 6 figures, accepted for publication in Experimental Astronomy

Transiting ultra-hot Jupiters are ideal candidates to study the exoplanet atmospheres and their dynamics, particularly by means of high-resolution, high signal-to-noise ratio spectra. One such object is KELT-20b, orbiting the fast rotating A2-type star KELT-20. Many atomic species have already been found in its atmosphere, with blueshifted signals that hints at the presence of a day-to-night side wind. We aimed to observe the atmospheric Rossiter-McLaughlin effect in the ultra-hot Jupiter KELT-20b, and to study any variation of the atmospheric signal during the transit. For this purpose, we analysed five nights of HARPS-N spectra covering five transits of KELT-20b. We computed the mean line profiles of the spectra with a least-squares deconvolution, and then we extracted the stellar radial velocities by fitting them with a rotational broadening profile in order to obtain the radial velocity time-series. We used the mean line profile residuals tomography to analyse the planetary atmospheric signal and its variations. We also used the cross-correlation method to study an already known double-peak feature in the FeI planetary signal. We observed both the classical and the atmospheric Rossiter-McLaughlin effect in the radial velocity time-series. The latter gave us an estimate of the radius of the planetary atmosphere that correlates with the stellar mask used in our work: R(p+atmo)/Rp = 1.13 +/- 0.02). We isolated the planetary atmospheric trace in the tomography, and we found radial velocity variations of the planetary atmospheric signal during transit with an overall blueshift of approximatively 10 km/s, along with small variations in the signal's depth and, less significant, in the full width at half maximum (FWHM). We also find a possible variation in the structure and position of FeI signal in different transits., Comment: 13 pages, 20 figures. Accepted for publication in A&A

In the framework of the GIARPS High-resolution Observations of T Tauri stars (GHOsT) project, we aim to characterize the atomic and molecular winds in a sample of classical T Tauri stars (CTTs) of the Taurus-Auriga region. We analyzed the flux calibrated [OI] 630 nm and $\rm H_2$ 2.12 $\rm ��m$ lines in a sample of 36 CTTs observed at the Telescopio Nazionale Galileo with the HARPS and GIANO spectrographs. We decomposed the line profiles into different kinematic Gaussian components and focused on the most frequently detected component, the narrow low-velocity (v$\rm_p < 20$ $\rm km$ $\rm s^{-1}$) component (NLVC). We found that the $\rm H_2$ line is detected in 17 sources ($\sim 50 \%$ detection rate), and [OI] is detected in all sources but one. The NLV components of the $\rm H_2$ and [OI] emission are kinematically linked, with a strong correlation between the peak velocities and the full widths at half maximum of the two lines. Assuming Keplerian broadening, we found that the [OI] NVLC originates from a disk region between 0.05 and 20 au and that of $\rm H_2$ in a region from 2 and 20 au. We did not find any clear correlation between v$\rm_p$ of the $\rm H_2$ and [OI] NVLC and the outer disk inclination. This result is in line with previous studies. Our results suggest that molecular and neutral atomic emission in disk winds originate from regions that might overlap, and that the survival of molecular winds in disks strongly depends on the gas exposure to the radiation from the central star. Our results demonstrate the potential of wide-band high-resolution spectroscopy in linking tracers of different manifestations of the same phenomenon., 22 pages, 10 figures, 6 tables, accepted for publication in A&A

Context. The existence of hot Jupiters is still not well understood. Two main channels are thought to be responsible for their current location: a smooth planet migration through the protoplanetary disk or the circularization of an initial highly eccentric orbit by tidal dissipation leading to a strong decrease in the semimajor axis. Different formation scenarios result in different observable effects, such as orbital parameters (obliquity and eccentricity) or frequency of planets at different stellar ages. Aims. In the context of the GAPS Young Objects project, we are carrying out a radial velocity survey with the aim of searching and characterizing young hot-Jupiter planets. Our purpose is to put constraints on evolutionary models and establish statistical properties, such as the frequency of these planets from a homogeneous sample. Methods. Since young stars are in general magnetically very active, we performed multi-band (visible and near-infrared) spectroscopy with simultaneous GIANO-B + HARPS-N (GIARPS) observing mode at TNG. This helps in dealing with stellar activity and distinguishing the nature of radial velocity variations: stellar activity will introduce a wavelength-dependent radial velocity amplitude, whereas a Keplerian signal is achromatic. As a pilot study, we present here the cases of two known hot Jupiters orbiting young stars: HD 285507 b and AD Leo b. Results. Our analysis of simultaneous high-precision GIARPS spectroscopic data confirms the Keplerian nature of the variation in the HD 285507 radial velocities and refines the orbital parameters of the hot Jupiter, obtaining an eccentricity consistent with a circular orbit. Instead, our analysis does not confirm the signal previously attributed to a planet orbiting AD Leo. This demonstrates the power of the multi-band spectroscopic technique when observing active stars., With funding from the Spanish government through the "María de Maeztu Unit of Excellence" accreditation (MDM-2017-0737)

Exoplanets orbiting very close to their host star are strongly irradiated. This can lead the upper atmospheric layers to expand and evaporate into space. The metastable helium (HeI) triplet at 1083.3nm has recently been shown to be a powerful diagnostic to probe extended and escaping exoplanetary atmosphere. We perform high-resolution transmission spectroscopy of the transiting hot Jupiter HD189733b with the GIARPS (GIANO-B + HARPS-N) observing mode of the Telescopio Nazionale Galileo, taking advantage of the simultaneous optical+near infrared spectral coverage to detect HeI in the planet's extended atmosphere and to gauge the impact of stellar magnetic activity on the planetary absorption signal. Observations were performed during five transit events of HD189733b. By comparison of the in- and out-of-transit GIANO-B observations we compute high-resolution transmission spectra, on which we perform equivalent width measurements and light-curves analyses to gauge the excess in-transit absorption in the HeI triplet. We detect an absorption signal during all five transits. The mean in-transit absorption depth amounts to 0.75+/-0.03%. We detect night-to-night variations in the HeI absorption signal likely due to the transit events occurring in presence of stellar surface inhomogeneities. We evaluate the impact of stellar-activity pseudo-signals on the true planetary absorption using a comparative analysis of the HeI and the H$\alpha$ lines. We interpret the time-series of the HeI absorption lines in the three nights not affected by stellar contamination -exhibiting a mean in-transit absorption depth of 0.77+/-0.04%- using a 3-d atmospheric code. Our simulations suggest that the helium layers only fill part of the Roche lobe. Observations can be explained with a thermosphere heated to $\sim$12000 K, expanding up to $\sim$1.2 planetary radii, and losing $\sim$1 g/s of metastable helium., Comment: 17 pages, 17 figures, accepted for publication in A&A

In the framework of the Global Architecture of Planetary Systems (GAPS) project we collected more than 300 spectra with HARPS-N at the TNG for the bright G9V star HD164922. This target is known to host one gas giant planet in a wide orbit (Pb~1200 days, semi-major axis ~2 au) and a Neptune-mass planet with a period Pc ~76 days. We searched for additional low-mass companions in the inner region of the system. We compared the radial velocities (RV) and the activity indices derived from the HARPS-N time series to measure the rotation period of the star and used a Gaussian process regression to describe the behaviour of the stellar activity. We exploited this information in a combined model of planetary and stellar activity signals in an RV time-series composed of almost 700 high-precision RVs, both from HARPS-N and literature data. We performed a dynamical analysis to evaluate the stability of the system and the allowed regions for additional potential companions. Thanks to the high sensitivity of the HARPS-N dataset, we detect an additional inner super-Earth with an RV semi-amplitude of 1.3+/-0.2 m/s, a minimum mass of ~4+/-1 M_E and a period of 12.458+/-0.003 days. We disentangle the planetary signal from activity and measure a stellar rotation period of ~42 days. The dynamical analysis shows the long term stability of the orbits of the three-planet system and allows us to identify the permitted regions for additional planets in the semi-major axis ranges 0.18-0.21 au and 0.6-1.4 au. The latter partially includes the habitable zone of the system. We did not detect any planet in these regions, down to minimum detectable masses of 5 and 18 M_E, respectively. A larger region of allowed planets is expected beyond the orbit of planet b, where our sampling rules-out bodies with minimum mass > 50 M_E., 23 pages, 16 Figures. Accepted for publication on A&A

We report on the discovery of periodic dips in the multiband lightcurve of ISO-ChaI 52, a young stellar object in the Chamaeleon I dark cloud. This is one among the peculiar objects that display very low or negligible accretion both in their UV continuum and spectral lines, although they present a remarkable infrared excess emission characteristic of optically-thick circumstellar disks. We have analyzed a VLT/X-Shooter spectrum with the tool ROTFIT to determine the stellar parameters. The latter, along with photometry from our campaign with the REM telescope and from the literature, have allowed us to model the spectral energy distribution and to estimate the size and temperature of the inner and outer disk. From the rotational period of the star/disk system of 3.45 days we estimate a disk inclination of 36$^\circ$. The depth of the dips in different bands has been used to gain information about the occulting material. A single extinction law is not able to fit the observed behavior, while a two-component model of a disk warp composed of a dense region with a gray extinction and an upper layer with an ISM-type extinction provides a better fit of the data., 11 pages, 11 figures; accepted for publication in Astronomy & Astrophysics

The detailed chemical composition of stars is important in many astrophysical fields, among which the characterisation of exoplanetary systems. Previous studies seem to indicate an anomalous chemical pattern of the youngest stellar population in the solar vicinity with a sub-solar metal content. This can influence various observational relations linking the properties of exoplanets to the characteristics of the host stars, for example the giant planet-metallicity relation. In this framework, we aim to expand our knowledge of the chemical composition of intermediate-age stars and understand whether these peculiarities are real or related to spectroscopic analysis techniques. We analysed high-resolution optical and near-infrared GIARPS spectra of intermediate-age stars (< 700Myr). To overcome issues related to the young ages of the stars, we applied a new spectroscopic method that uses titanium lines to derive the atmospheric parameters, in particular surface gravities and microturbulence velocity parameter. We also derived abundances of 14 different atomic species. The lack of systematic trends between elemental abundances and effective temperatures validates our method. However, we observed that the coolest (, 18 pages, 9 figures, accepted for publication in A&A

[Context] Most of our current knowledge on planet formation is still based on the analysis of main sequence, solar-type stars. Conversely, detailed chemical studies of large samples of M dwarfs hosting planets are still missing., [Aims] Correlations exist between the presence of different types of planets around FGK stars and metallicity, individual chemical abundance, and stellar mass. We aim to test whether or not these correlations still hold for the less-massive M dwarf stars. Methods to determine stellar abundances of M dwarfs from high-resolution optical spectra in a consistent way are still missing. The present work is a first attempt to fill this gap., [Methods] We analyse a large sample of M dwarfs with and without known planetary companions in a coherent and homogeneous way. We develop for the first time a methodology to determine stellar abundances of elements other than iron for M dwarf stars from high-resolution optical spectra. Our methodology is based on the use of a principal component analysis and sparse Bayesian methods. We made use of a set of M dwarfs orbiting around an FGK primary with known abundances to train our methods. We applied our methods to derive stellar metalliticies and abundances of a large sample of M dwarfs observed within the framework of current radial-velocity surveys. We then used a sample of nearby FGK stars to cross-validate our technique by comparing the derived abundance trends in the M dwarf sample with those found on the FGK stars., [Results] The metallicity distribution of the different subsamples reveals a correlation between the metallicities of M dwarfs and their probability of hosting giant planets. We also find a correlation between this latter probability and stellar mass. M dwarfs hosting low-mass planets do not seem to follow the so-called planet–metallicity correlation. We also find that the frequency of low-mass planets does not depend on the mass of the stellar host. These results appear to be in agreement with those of previous works. However, we note that for giant-planet hosts our metallicities predict a weaker planet–host metallicity correlation but a stronger mass-dependency than corresponding values derived from photometric results. We show for the first time that there seems to be no differences between M dwarfs with and without known planets in terms of their abundance distributions of elements different from iron., [Conclusions] Our data show that low-mass stars with planets follow the same metallicity, mass, and abundance trends as their FGK counterparts, which are usually explained within the framework of core-accretion models., This research was supported by the Italian Ministry of Education, University, and Research through the PREMIALE WOW 2013 research project under grant Ricerca di pianeti intorno a stelle di piccola massa. J.M. acknowledges support from the Accordo Attuativo ASI-INAF n. 2018.22.HH.O, Partecipazione alla fase B1 della missione Ariel (ref. G. Micela). M.P., I.R., J.C.M, and E.H acknowledge support from the Spanish Ministry of Science and Innovation and the European Regional Development Fund through grant PGC2018-098153-BC33, as well as the support of the Generalitat de Catalunya/CERCA programme. J.I.G.H. acknowledges financial support from Spanish Ministry of Science and Innovation (MICINN) under the 2013 Ramón y Cajal program RYC-2013-14875. A.S.M. acknowledges financial support from the Spanish MICINN under the 2019 Juan de la Cierva Programme. B.T.P. acknowledges Fundación La Caixa for the financial support received in the form of a Ph.D. contract. J.I.G.H., R.R., A.S.M., B.T.P. acknowledge financial support from the Spanish MICINN AYA2017-86389-P. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement.

Detecting and characterising exoworlds around very young stars (age$, Comment: Accepted for publication on Astronomy and Astrophysics. Abstract slightly modified to fulfill arxiv requirements

Open clusters exquisitely track the Galactic disc chemical properties and its time evolution; a substantial number of studies and large spectroscopic surveys focus mostly on the chemical content of relatively old clusters (age $\gtrsim$ 1 Gyr). Interestingly, the less studied young counterpart populating the solar surrounding has been found to be solar (at most), with a notable surprising lack of young metal-rich objects. While there is wide consensus about the moderately above-solar composition of the Hyades cluster, the metallicity of Praesepe is still controversial. Recent studies suggest that these two clusters share identical chemical composition and age, but this conclusion is disputed. With the aim of reassessing the metallicity of Praesepe, and its difference (if any) with the Hyades cluster, we present in this paper a spectroscopic investigation of ten solar-type dwarf members. We exploited $GIARPS$ at the TNG to acquire high-resolution, high-quality optical and near-IR spectra and derived stellar parameters, metallicity ([Fe/H]), light elements, $\alpha$- and iron-peak elements, by using a strictly differential (line-by-line) approach. We also analysed in the very same way the solar spectrum and the Hyades solar analogue HD 28099. Our findings suggest that Praesepe is more metal-rich than the Hyades, at the level of $\Delta$[Fe/H]=+0.05$\pm$0.01 dex, with a mean value of [Fe/H]=+0.21$\pm0.01$ dex. All the other elements scale with iron, as expected. This result seems to reject the hypothesis of a common origin for these two open clusters. Most importantly, Praesepe is currently the most metal-rich, young open cluster living in the solar neighbourhood., Comment: 13 pages, 5 figures. Accepted for publication in A&A

In the framework of the GAPS project, we observed the planet-hosting star KELT-9 (A-type star, VsinI$\sim$110 km/s) with the HARPS-N spectrograph at the TNG. In this work we analyse the spectra and the extracted radial velocities (RVs), to constrain the physical parameters of the system and to detect the planetary atmosphere of KELT-9b. We extracted from the high-resolution optical spectra the mean stellar line profiles with an analysis based on the Least Square Deconvolution technique. Then, we computed the stellar RVs with a method optimized for fast rotators, by fitting the mean stellar line profile with a purely rotational profile instead of using a Gaussian function. The new spectra and analysis led us to update the orbital and physical parameters of the system, improving in particular the value of the planetary mass to $M_{\rm p}=2.88\pm0.35\,M_{\rm Jup}$. We discovered an anomalous in-transit RV deviation from the theoretical Rossiter-McLaughlin effect solution, calculated from the projected spin-orbit angle $\lambda=-85.78\pm0.46$ degrees measured with Doppler tomography. We prove that this deviation is caused by the planetary atmosphere of KELT-9b, thus we name this effect Atmospheric Rossiter-McLaughlin effect. By analysing the magnitude of the RV anomaly, we obtained information on the extension of the planetary atmosphere as weighted by the model used to retrieve the stellar mean line profiles, which is up to $1.22\pm0.02\,R_{\rm p}$. The Atmospheric Rossiter-McLaughlin effect will be observable for other exoplanets whose atmosphere has non-negligible correlation with the stellar mask used to retrieve the RVs, in particular ultra-hot Jupiters with iron in their atmosphere. The duration and amplitude of the effect will depend not only on the extension of the atmosphere, but also on the in-transit planetary RVs and on the projected rotational velocity of the parent star., Comment: accepted for publication in A&A. Language edited version

We report on the accretion properties of low-mass stars in the LH95 association within the Large Magellanic Cloud (LMC). Using non-contemporaneous wide-band and narrow-band photometry obtained with the HST, we identify 245 low-mass pre-main sequence (PMS) candidates showing H$\alpha$ excess emission above the 4$\sigma$ level. We derive their physical parameters, i.e. effective temperatures, luminosities, masses ($M_\star$), ages, accretion luminosities, and mass accretion rates ($\dot M_{\rm acc}$). We identify two different stellar populations: younger than ~8Myr with median $\dot M_{\rm acc}$~5.4x10$^{-8}M_\odot$/yr (and $M_\star$~0.15-1.8$M_\odot$) and older than ~8Myr with median $\dot M_{\rm acc}$~4.8x10$^{-9}M_\odot$/yr (and $M_\star$~0.6-1.2$M_\odot$). We find that the younger PMS candidates are assembled in groups around Be stars, while older PMS candidates are uniformly distributed within the region without evidence of clustering. We find that $\dot M_{\rm acc}$ in LH95 decreases with time more slowly than what is observed in Galactic star-forming regions (SFRs). This agrees with the recent interpretation according to which higher metallicity limits the accretion process both in rate and duration due to higher radiation pressure. The $\dot M_{\rm acc}-M_\star$ relationship shows different behaviour at different ages, becoming progressively steeper at older ages, indicating that the effects of mass and age on $\dot M_{\rm acc}$ cannot be treated independently. With the aim to identify reliable correlations between mass, age, and $\dot M_{\rm acc}$, we used for our PMS candidates a multivariate linear regression fit between these parameters. The comparison between our results with those obtained in other SFRs of our Galaxy and the MCs confirms the importance of the metallicity for the study of the $\dot M_{\rm acc}$ evolution in clusters with different environmental conditions., Comment: Accepted for publication in ApJ; 26 pages, 12 pages, 3 tables; abstract shortened. Fixed a typo in the name of a co-author

The mechanism for jet formation in the disks of T Tauri stars is poorly understood. Observational benchmarks to launching models can be provided by tracing the physical properties of the kinematic components of the wind and jet in the inner 100 au of the disk surface. In the framework of the GHOsT (GIARPS High-resolution Observations of T Tauri stars) project, we aim to perform a multi-line analysis of the velocity components of the gas in the jet acceleration zone. We analyzed the GIARPS-TNG spectra of six objects in the Taurus-Auriga complex (RY Tau, DG Tau, DL Tau, HN Tau, DO Tau, RW Aur A). Thanks to the combined high-spectral resolution (R=50000-115000) and wide spectral coverage (~400-2400 nm) we observed several O, S+, N, N+, and Fe+ forbidden lines spanning a large range of excitation and ionization conditions. In four objects (DG Tau, HN Tau, DO Tau, RW Aur A), temperature (T_e), electron and total density (n_e, n_H), and fractional ionization (x_e) were derived as a function of velocity through an excitation and ionization model. The abundance of gaseous iron, X(Fe), a probe of the dust content in the jet, was derived in selected velocity channels. The physical parameters vary smoothly with velocity, suggesting a common origin for the different kinematic components. In DG Tau and HN Tau, T_e, x_e, and X(Fe) increase with velocity (roughly from 6000 K, 0.05, 10% X(Fe)_sun to 15000 K, 0.6, 90% X(Fe)_sun). This trend is in agreement with disk-wind models in which the jet is launched from regions of the disk at different radii. In DO Tau and RW Aur A, we infer x_e < 0.1, n_H ~10^6-7 cm^-3, and X(Fe), Comment: Accepted by A&A

We report the results of a survey on the [OI]6300A line emission in 131 T Tauri stars of the Lupus, Chamaeleon and σ Orionis star forming regions, observed with the X-shooter spectrograph at the Very Large Telescope (VLT). The line profile was deconvolved into a low velocity component (LVC, ∣Vr∣ 40 km s−1), originating from slow winds and high velocity jets, respectively. The LVC is by far the most frequent component, with a detection rate of 77%, while only 30% of sources have a HVC. The [OI]6300A luminosity of both the LVC and HVC, when detected, correlates with stellar and accretion parameters of the central sources with similar slopes for the two components. Mass ejection rates (\({\dot {M}_{jet}}\)) measured from the detected HVC [OI]6300A line luminosity span from ∼10−13 to ∼10−7 M⊙ yr−1 and the corresponding \({\dot {M}_{jet}}\)/\({\dot {M}_{acc}}\) ratio ranges from ∼0.01 to ∼0.5, with an average value of 0.07. However, considering the upper limits on the HVC, we infer a \({\dot {M}_{jet}}\)/\({\dot {M}_{acc}}\) ratio < 0.03 in more than 40% of sources. We argue that most of these sources might lack the physical conditions needed for an efficient magneto-centrifugal acceleration in the star-disc interaction region.

Statistical studies of exoplanets have shown that giant planets are more commonly hosted by metal-rich dwarf stars than low-metallicity ones, while such a correlation is not evident for lower-mass planets. The search for giant planets around metal-poor stars and the estimate of their occurrence $f_p$ is an important element in providing support to models of planet formation. We present results from the HARPS-N search for giant planets orbiting metal-poor ($-1.0\leq[Fe/H]\leq-0.5$ dex) stars in the northern hemisphere complementing a previous HARPS survey on southern stars in order to update the estimate of $f_p$. High-precision HARPS-N observations of 42 metal-poor stars are used to search for planetary signals to be fitted using differential evolution MCMC single-Keplerian models. We then join our detections to the results of the previous HARPS survey on 88 metal-poor stars to provide a preliminar estimate of the two-hemisphere $f_p$. We report the detection of two new giant planets around HD 220197 and HD 233832. The first companion has M$\sin{i}=0.20_{-0.04}^{+0.07}$ M$_{\rm Jup}$ and orbital period of $1728_{-80}^{+162}$ days, and for the second companion we find two solutions of equal statistical weight having periods $2058_{-40}^{+47}$ and $4047_{-117}^{+91}$ days and minimum masses of $1.78_{-0.06}^{+0.08}$ and $2.72_{-0.23}^{+0.23}$ M$_{\rm Jup}$, respectively. Joining our two detections with the three from the southern survey we obtain a preliminary and conservative estimate of global frequency of $f_p=3.84_{-1.06}^{+2.45}\%$ for giant planets around metal-poor stars. The two new giant planets orbit dwarf stars at the metal-rich end of the HARPS-N metal-poor sample, corroborating previous results suggesting that giant planet frequency still is a rising function of host star [Fe/H]. We also note that all detections in the overall sample are giant long-period planets., Comment: 15 pages, 8 figures, 5 tables, accepted for publication in A&A

The {\it Kepler} space mission and its {\it K2} extension provide photometric time series data with unprecedented accuracy. These data challenge our current understanding of the metallic-lined A stars (Am stars) for what concerns the onset of pulsations in their atmospheres. It turns out that the predictions of current diffusion models do not agree with observations. To understand this discrepancy, it is of crucial importance to obtain ground-based spectroscopic observations of Am stars in the {\it Kepler} and {\it K2} fields in order to determine the best estimates of the stellar parameters. In this paper, we present a detailed analysis of high-resolution spectroscopic data for seven stars previously classified as Am stars. We determine the effective temperatures, surface gravities, projected rotational velocities, microturbulent velocities and chemical abundances of these stars using spectral synthesis. These spectra were obtained with {\it CAOS}, a new instrument recently installed at the observing station of the Catania Astrophysical Observatory on Mt. Etna. Three stars have already been observed during quarters Q0-Q17, namely: HD\,180347, HD\,181206, and HD\,185658, while HD\,43509 was already observed during {\it K2} C0 campaign. We confirm that HD\,43509 and HD\,180347 are Am stars, while HD 52403, HD\,50766, HD\,58246, HD\,181206 and HD\,185658 are marginal Am stars. By means of non-LTE analysis, we derived oxygen abundances from O{\sc I}$\lambda$7771--5{\AA} triplet and we also discussed the results obtained with both non-LTE and LTE approaches., Comment: accepted in MNRAS main journal 13 pages, 11 figures, 3 tables. arXiv admin note: text overlap with arXiv:1404.0954

We have analysed the [OI]6300 A line in a sample of 131 young stars with discs in the Lupus, Chamaeleon and signa Orionis star forming regions, observed with the X-shooter spectrograph at VLT. The stars have mass accretion rates spanning from 10^{-12} to 10^{-7} Mo/yr. The line profile was deconvolved into a low velocity component (LVC, < 40 km/s) and a high velocity component (HVC, > 40 km/s ), originating from slow winds and high velocity jets, respectively. The LVC is by far the most frequent component, with a detection rate of 77%, while only 30% of sources have a HVC. The [OI]6300 luminosity of both the LVC and HVC, when detected, correlates with stellar and accretion parameters of the central sources (i.e. Lstar , Mstar , Lacc , Macc), with similar slopes for the two components. The line luminosity correlates better with the accretion luminosity than with the stellar luminosity or stellar mass. We suggest that accretion is the main drivers for the line excitation and that MHD disc-winds are at the origin of both components. In the sub-sample of Lupus sources observed with ALMA a relationship is found between the HVC peak velocity and the outer disc inclination angle, as expected if the HVC traces jets ejected perpendicularly to the disc plane. Mass loss rates measured from the HVC span from ~ 10^{-13} to ~10^{-7} Mo/yr. The corresponding Mloss/Macc ratio ranges from ~0.01 to ~0.5, with an average value of 0.07. However, considering the upper limits on the HVC, we infer a ratio < 0.03 in more than 40% of sources. We argue that most of these sources might lack the physical conditions needed for an efficient magneto-centrifugal acceleration in the star-disc interaction region. Systematic observations of populations of younger stars, that is, class 0/I, are needed to explore how the frequency and role of jets evolve during the pre-main sequence phase., 15 pages, 14 figures, Accepted for publication in A&A

We present the results of a study of the stellar and accretion properties of the (almost) complete sample of class II and transitional YSOs in the Lupus I, II, III and IV clouds, based on spectroscopic data acquired with the VLT/X-Shooter spectrograph. Our study combines the dataset from our previous work with new observations of 55 additional objects. We have investigated 92 YSO candidates in total, 11 of which have been definitely identified with giant stars unrelated to Lupus. The stellar and accretion properties of the 81 bona fide YSOs, which represent more than 90% of the whole class~II and transition disc YSO population in the aforementioned Lupus clouds, have been homogeneously and self-consistently derived, allowing for an unbiased study of accretion and its relationship with stellar parameters. The accretion luminosity, Lacc, increases with the stellar luminosity, Lstar, with an overall slope of ~1.6, similar but with a smaller scatter than in previous studies. There is a significant lack of strong accretors below Lstar~0.1Lsun, where Lacc is always lower than 0.01Lstar. We argue that the Lacc-Lstar slope is not due to observational biases, but is a true property of the Lupus YSOs. The logMacc-logMstar correlation shows a statistically significant evidence of a break, with a steeper relation for Mstar, 43 pages, 22 figures

Context. Identification of planetary companions of giant stars is made difficult because of the astrophysical noise, that may produce radial velocity (RV) variations similar to those induced by a companion. On the other hand any stellar signal is wavelength dependent, while signals due to a companion are achromatic. Aims. Our goal is to determine the origin of the Doppler periodic variations observed in the thick disk K giant star TYC 4282-605-1 by HARPS-N at the Telescopio Nazionale Galileo (TNG) and verify if they can be due to the presence of a substellar companion. Methods. Several methods have been used to exclude the stellar origin of the observed signal including detailed analysis of activity indicators and bisector and the analysis of the photometric light curve. Finally we have conducted an observational campaign to monitor the near infrared (NIR) RV with GIANO at the TNG in order to verify whether the NIR amplitude variations are comparable with those observed in the visible. Results. Both optical and NIR RVs show consistent variations with a period at 101 days and similar amplitude, pointing to the presence of a companion orbiting the target. The main orbital properties obtained for our giant star with a derived mass of M=0.97+-0.03M_sun are M_Psini=10.78+-0.12MJ;P=101.54+-0.05days;e=0.28+-0.01 and a=0.422+-0.009AU. The chemical analysis shows a significant enrichment in the abundance of Nai, Mgi, Ali and S i while the rest of analyzed elements are consistent with the solar value demonstrating that the chemical composition corresponds with an old K giant (age = 10.1 Gyr) belonging to local thick disk. Conclusions. We conclude that the substellar companion hypothesis for this K giant is the best explanation for the observed periodic RV variation. This study also shows the high potential of multi-wavelength RV observations for the validation of planet candidates., Comment: Accepted in Journal reference A&A 14/06/2017

We used the TNG/GIANO instrument to obtain near-IR high-resolution spectra (R~50000) of XZ Tau and DR Tau, two actively accreting T Tauri stars classified as EXors. The analysis of the observed features provides information on the properties of the inner disk, the accretion columns, and the winds. Both sources display composite HI line profiles, with contributions from both accreting gas and high-velocity winds. These lines become more symmetric and narrower with increasing upper energy, which may be interpreted in terms of two components with different decrements or imputed to self-absorption effects. XZ Tau shows a relatively high state of activity with respect to literature observations. The variation of the HeI 1.08um line blue-shifted absorption suggests that the inner wind has undergone a dramatic change in its velocity structure, connected with a recent accretion event. DR Tau has a more stable wind as its HeI 1.08um absorption is stable in time in spite of strong variability of the emission component. The IR veiling can be interpreted as due to blackbody emission at temperatures of 1600K for XZ Tau and 2300K DR Tau, with emitting areas ~30 times larger than the star. For XZ Tau these conditions are consistent with emission from the inner rim of the dusty disk, while for DR Tau the fairly high temperature may suggest an origin from a thick gaseous disk within the dust sublimation radius. Strong and broad metallic lines, mainly from CI and FeI, are detected in XZ Tau, similar to those observed in other EXor sources during burst phases. DR Tau shows weaker and narrower metallic lines, despite its larger accretion luminosity. This suggests that accretion is not the only driver of metallic line excitation. Our observations show the potential of wide-band, high-resolution near-IR spectroscopy to simultaneously probe the phenomena that occur in the star-disk interaction region., Comment: 15 pages, accepted by A&A

A homogeneous determination of basic stellar parameters of young stellar object (YSO) candidates is needed to confirm their evolutionary stage, membership to star forming regions (SFRs), and to get reliable values of the quantities related to chromospheric activity and accretion. We used the code ROTFIT and synthetic BT-Settl spectra for the determination of the atmospheric parameters (Teff and logg), the veiling, the radial (RV) and projected rotational velocity (vsini), from X-Shooter spectra of 102 YSO candidates in the Lupus SFR. We have shown that 13 candidates can be rejected as Lupus members based on their discrepant RV with respect to Lupus and/or the very low logg values. At least 11 of them are background giants. The spectral subtraction of inactive templates enabled us to measure the line fluxes for several diagnostics of both chromospheric activity and accretion. We found that all Class-III sources have H$\alpha$ fluxes compatible with a pure chromospheric activity, while objects with disks lie mostly above the boundary between chromospheres and accretion. YSOs with transitional disks displays both high and low H$\alpha$ fluxes. We found that the line fluxes per unit surface are tightly correlated with the accretion luminosity ($L_{\rm acc}$) derived from the Balmer continuum excess. This rules out that the relationships between $L_{\rm acc}$ and line luminosities found in previous works are simply due to calibration effects. We also found that the CaII-IRT flux ratio, $F_{8542}/F_{8498}$, is always small, indicating an optically thick emission source. The latter can be identified with the accretion shock near the stellar photosphere. The Balmer decrement reaches instead, for several accretors, high values typical of optically thin emission, suggesting that the Balmer emission originates in different parts of the accretion funnels with a smaller optical depth., Comment: 28 pages, 26 figures, accepted by A&A

Context. M dwarfs are prime targets for current and future planet search programs, particularly those focused on the detection and characterization of rocky planets in the habitable zone. In this context, understanding their magnetic activity is important for two main reasons: it affects our ability to detect small planets and it plays a key role in the characterization of the stellar environment. Aims: We analyze observations of the Ca II H&K and Hα lines as diagnostics of chromospheric activity for low-activity early-type M dwarfs. Methods: We analyze the time series of spectra of 71 early-type M dwarfs collected in the framework of the HADES project for planet search purposes. The HARPS-N spectra simultaneously provide the Ca II H&K doublet and the Hα line. We develop a reduction scheme able to correct the HARPS-N spectra for instrumental and atmospheric effects, and also to provide flux-calibrated spectra in units of flux at the stellar surface. The Ca II H&K and Hα fluxes are then compared with each other, and their time variability is analyzed. Results: We find that the Ca II H and K flux excesses are strongly correlated with each other, while the Hα flux excess is generally less correlated with the Ca II H&K doublet. We also find that Hα emission does not increase monotonically with the Ca II H&K line flux, showing some absorption before being filled in by chromospheric emission when Ca II H&K activity increases. Analyzing the time variability of the emission fluxes, we derive a tentative estimate of the rotation period (on the order of a few tens of days) for some of the program stars, and the typical lifetime of chromospheric active regions (on the order of a few stellar rotations). Conclusions: Our results are in good agreement with similar previous studies. In particular, we find evidence that the chromospheres of early-type M dwarfs could be characterized by different filament coverage, affecting the formation mechanism of the Hα line. We also show that chromospheric structure is likely related to spectral type.

With the purpose of performing a homogeneous determination of elemental abundances for members of the Lupus T association, we analyzed three chemical elements: lithium, iron, and barium. The aims were: to derive the Li abundance for ~90% of known class II stars in the Lupus I, II, III, IV clouds; to perform chemical tagging of a region where few Fe abundance measurements have been obtained in the past, and no determination of the Ba content has been done up to now. We also investigated possible Ba enhancement, as this element has become increasingly interesting in the last years following the evidence of Ba over-abundance in young clusters, the origin of which is still unknown. Using X-shooter@VLT, we analyzed the spectra of 89 cluster members, both class II and III stars. We measured the strength of the Li line and derived the abundance of this element through equivalent width measurements and curves of growth. For six class II stars we also measured the Fe and Ba abundances using the spectral synthesis and the code MOOG. The veiling contribution was taken into account for all three elements. We find a dispersion in the strength of the Li line at low Teff and identify three targets with severe Li depletion. The nuclear age inferred for these highly Li-depleted stars is around 15 Myr, which exceeds the isochronal one. As in other star-forming regions, no metal-rich members are found in Lupus, giving support to a recent hypothesis that the Fe abundance distribution of most of the nearby young regions could be the result of a common and widespread star formation episode involving the Galactic thin disk. We find that Ba is over-abundant by ~0.7 dex with respect to the Sun. Since current theoretical models cannot reproduce this Ba abundance pattern, we investigated whether this unusually large Ba content might be related to effects due to stellar parameters, stellar activity, and accretion., 15 pages, 14 figures, 3 tables; accepted for publication in A&A; abstract shortened

Characterization of the properties of young brown dwarfs are important to constraining the formation of objects at the extreme low-mass end of the initial mass function. While young brown dwarfs share many properties with solar-mass T Tauri stars, differences may be used as tests of how the physics of accretion/outflow and disk chemistry/dissipation depend on the mass of the central object. This article summarizes the presentations and discussions during the splinter session on “Disks, accretion and outflows of brown dwarfs” held at the CoolStars17 conference in Barcelona in June 2012. Recent results in the field of brown dwarf disks and outflows include the determination of brown dwarf disk masses and geometries based on Herschel far-IR photometry (70–160 µm), accretion properties based on X-Shooter spectra, and new outflow detections in the very low-mass regime. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

(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 present the results of our analysis on V1481 Ori (JW 239), a young SB2 in the Orion Nebula Cluster with a circumbinary disc accreting on the lower-mass component. The analysis is based on high-resolution spectroscopic data and high-quality photometric time series about 20-yr long. Thanks to the spectroscopy, we confirm the binary nature of this system consisting of M3 + M4 components and derive the mass ratio M_B/M_A = 0.54, a variable luminosity ratio L_B/L_A = 0.68--0.94, and an orbital period P_orb = 4.433d. The photometric data allowed us to measure the rotation periods of the two components P_phot = 4.4351d and they are found to be synchronized with the orbital period. The simultaneous modeling of V-, I-band, and radial velocity curves in the 2005 season suggests that the variability is dominated by one hot spot on the secondary component covering at least about 3.5% of the stellar surface and about 420K hotter than the unperturbed photosphere. Such a spot may originate from the material of the circumbinary disc accreting onto the secondary component. We also detect an apparent 6-yr periodic variation in the position of this hot spot, which is inferred from the phase migration of the light curve maximum, which we interpret as due to either the presence of surface differential rotation as large as 0.065%, a value compatible with the fully convective components, or to a periodic exchange of angular momentum between the disc and the star, which implies a minimum magnetic field strength of 650G at the stellar surface., Comment: 13 pages, 8 figures, 6 tables, 1 online table, Accepted by MNRAS

Recently, several studies have shown that young, open clusters are characterised by a considerable over-abundance in their barium content. In particular, D'Orazi et al. (2009) reported that in some younger clusters [Ba/Fe] can reach values as high as ~0.6 dex. The work also identified the presence of an anti-correlation between [Ba/Fe] and cluster age. For clusters in the age range ~4.5 Gyr-500 Myr, this is best explained by assuming a higher contribution from low-mass asymptotic giant branch stars to the Galactic chemical enrichment. The purpose of this work is to investigate the ubiquity of the barium over-abundance in young stellar clusters. We analysed high-resolution spectroscopic data, focusing on the s-process elemental abundance for three nearby young associations, i.e. AB Doradus, Carina-Near, and Ursa Major. The clusters have been chosen such that their age spread would complement the D'Orazi et al. (2009) study. We find that while the s-process elements Y, Zr, La, and Ce exhibit solar ratios in all three associations, Ba is over-abundant by ~0.2 dex. Current theoretical models can not reproduce this abundance pattern, thus we investigate whether this unusually large Ba content might be related to chromospheric effects. Although no correlation between [Ba/Fe] and several activity indicators seems to be present, we conclude that different effects could be at work which may (directly or indirectly) be related to the presence of hot stellar chromospheres.

During the study of a large set of late-type stellar X-ray sources, we discovered a large fraction of multiple systems. In this paper we investigate the orbital elements and kinematic properties of three new spectroscopic triple systems as well as spectral types and astrophysical parameters (T_eff, log g, vsin i, log N(Li)) of their components. We conducted follow-up optical observations, both photometric and spectroscopic at high resolution, of these systems. We used a synthetic approach and the cross-correlation method to derive most of the stellar parameters. We estimated reliable radial velocities and deduced the orbital elements of the inner binaries. The comparison of the observed spectra with synthetic composite ones, obtained as the weighted sum of three spectra of non-active reference stars, allowed us to determine the stellar parameters for each component of these systems. We found all are only composed of main sequence stars. These three systems are certainly stable hierarchical triples composed of short-period inner binaries plus a tertiary component in a long-period orbit. From their kinematics and/or Lithium content, these systems result to be fairly young., Comment: Accepted for publication in A&A (on July 22, 2008)

Aims.We present the results of a contemporaneous photometric and spectroscopic monitoring of two RS CVn binaries, namely And and II Peg. The aim of this work is to investigate the behavior of surface inhomogeneities in the atmospheres of the active components of these systems that have nearly the same temperatures but different gravities.Methods.The light curves and the modulation of the surface temperature, as recovered from line-depth ratios (LDRs), were used to map the photospheric spots, while the H emission was used as an indicator of chromospheric inhomogeneities. The spot temperatures and sizes were derived from a spot model applied to the contemporaneous light and temperature curves.Results.We find larger and cooler spots on II Peg (T sp ? 3600K); than on And (T sp ? 3900K); this could be the result of both the difference in gravity and the higher activity level of the former. Moreover, we find a clear anti-correlation between the H? emission and the photospheric diagnostics (temperature and light curves). We have detected a modulation in the intensity of the He I D3 line with the star rotation, suggesting surface features also in the upper chromosphere of these stars. A rough reconstruction of the 3D structure of their atmospheres was also performed by applying a spot/plage model to the light and temperature curves and to the H flux modulation. In addition, a strong flare affecting the H?, the He I D3, and the cores of Na I D1,2 lines has been observed on II Peg.Conclusions.The spot/plage configuration has been reconstructed in the visible component of ? And and II Peg, which have nearly the same temperature but very different gravities and rotation periods. A close spatial association of photospheric and chromospheric active regions, at the time of our observations, was found in both stars. Larger and cooler spots were found on II Peg, the system with the active component of higher gravity and a higher activity level. The area ratio of plages to spots seems to decrease when the spots get bigger. Moreover, with both this and literature data, a correlation between the temperature difference ? = T ph - Tspand the surface gravity is also suggested. © 2008 ESO.

We present a photometric and spectroscopic study of four G-K dwarfs, namely HD 166, epsilon Eri, chi1 Ori and kappa1 Cet. In three cases, we find a clear spatial association between photospheric and chromospheric active regions. For chi1 Ori we do not find appreciable variations of photospheric temperature, and chromospheric Halpha emission. We applied a spot/plage model to the observed rotational modulation of temperature and flux to derive spot/plage parameters and to reconstruct a rough three-dimensional map of the outer atmosphere of kappa1 Cet, HD 166 and epsilon Eri.

We determine the true and the projected obliquity of HAT-P-36 and WASP-11/HAT-P-10 systems, respectively, which are both composed of a relatively cool star and a hot-Jupiter planet. Thanks to the high-resolution spectrograph HARPS-N, we observed the Rossiter-McLaughlin effect for both the systems by acquiring precise radial-velocity measurements during planetary transit events. We also present photometric observations comprising six light curves covering five transit events, obtained using three medium-class telescopes and the telescope-defocussing technique. One transit of WASP-11/HAT-P-10 was followed simultaneously from two observatories. The three transit light curves of HAT-P-36b show anomalies that are attributable to starspot complexes on the surface of the parent star, in agreement with the analysis of its spectra that indicate a moderate activity. By analysing the complete HATNet data set of HAT-P-36, we estimated the stellar rotation period by detecting a periodic photometric modulation in the light curve caused by star spots, obtaining Prot=15.3 days, which implies that the inclination of the stellar rotational axis with respect to the line of sight is 65 degree. We used the new spectroscopic and photometric data to revise the main physical parameters and measure the sky-projected misalignment angle of the two systems. We found \lambda=-14 degree for HAT-P-36 and \lambda=7 degree for WASP-11/HAT-P-10, indicating in both cases a good spin-orbit alignment. In the case of HAT-P-36, we also measured its real obliquity, which turned out to be 25 degrees., Comment: 18 pages, 14 figures

XO-2 is the first confirmed wide stellar binary system where the almost twin components XO-2N and XO-2S have planets. This stimulated a detailed characterization study of the stellar and planetary components based on new observations. We collected high-resolution spectra with the HARPS-N spectrograph and multi-band light curves. Spectral analysis led to an accurate determination of the stellar atmospheric parameters and characterization of the stellar activity. We collected 14 transit light curves of XO-2Nb used to improve the transit parameters. Photometry provided accurate magnitude differences between the stars and a measure of their rotation periods. The iron abundance of XO-2N was found to be +0.054 dex greater, within more than 3-sigma, than that of XO-2S. We confirm a long-term variation in the radial velocities of XO-2N, and we detected a turn-over with respect to previous measurements. We suggest the presence of a second massive companion in an outer orbit or the stellar activity cycle as possible causes of the observed acceleration. The latter explanation seems more plausible with the present dataset. We obtained an accurate value of the projected spin-orbit angle for the XO-2N system (lambda=7+/-11 degrees), and estimated the real 3-D spin-orbit angle (psi=27 +12/-27 degrees). We measured the XO-2 rotation periods, and found a value of P=41.6 days in the case of XO-2N, in excellent agreement with the predictions. The period of XO-2S appears shorter, with an ambiguity between 26 and 34.5 days that we cannot solve with the present dataset alone. XO-2N appears to be more active than the companion, and this could be due to the fact that we sampled different phases of their activity cycle, or to an interaction between XO-2N and its hot Jupiter that we could not confirm., 26 pages, 25 figures, accepted for publication in Astronomy and Astrophysics

Aims. For more than 1.5 years we monitored spectroscopically the star KELT-6 (BD+312447), known to host the transiting hot Saturn KELT-6b, because a previously observed long-term trend in radial velocity time series suggested the existence of an outer companion. Methods. We collected a total of 93 new spectra with the HARPS-N and TRES spectrographs. A spectroscopic transit of KELT-6b was observed with HARPS-N, and simultaneous photometry was obtained with the IAC-80 telescope. Results. We proved the existence of an outer planet with a mininum mass M$_{\rm p}$sini=3.71$\pm$0.21 M$_{\rm Jup}$ and a moderately eccentric orbit ($e=0.21_{-0.036}^{+0.039}$) of period P$\sim$3.5 years. We improved the orbital solution of KELT-6b and obtained the first measurement of the Rossiter-McLaughlin effect, showing that the planet has a likely circular, prograde, and slightly misaligned orbit, with a projected spin-orbit angle $\lambda$=$-$36$\pm$11 degrees. We improved the KELT-6b transit ephemeris from photometry, and we provided new measurements of the stellar parameters. KELT-6 appears as an interesting case to study the formation and evolution of multi-planet systems., Comment: Letter, 4 figures, accepted for publication in A&A. Some language editing and numbering of the paper series changed (from X to IX)

Binary stars hosting exoplanets are a unique laboratory where chemical tagging can be performed to measure with high accuracy the elemental abundances of both stellar components, with the aim to investigate the formation of planets and their subsequent evolution. Here, we present a high-precision differential abundance analysis of the XO-2 wide stellar binary based on high resolution HARPS-N@TNG spectra. Both components are very similar K-dwarfs and host planets. Since they formed presumably within the same molecular cloud, we expect they should possess the same initial elemental abundances. We investigate if the presence of planets can cause some chemical imprints in the stellar atmospheric abundances. We measure abundances of 25 elements for both stars with a range of condensation temperature $T_{\rm C}=40-1741$ K, achieving typical precisions of $\sim 0.07$ dex. The North component shows abundances in all elements higher by $+0.067 \pm 0.032$ dex on average, with a mean difference of +0.078 dex for elements with $T_{\rm C} > 800$ K. The significance of the XO-2N abundance difference relative to XO-2S is at the $2\sigma$ level for almost all elements. We discuss the possibility that this result could be interpreted as the signature of the ingestion of material by XO-2N or depletion in XO-2S due to locking of heavy elements by the planetary companions. We estimate a mass of several tens of $M_{\oplus}$ in heavy elements. The difference in abundances between XO-2N and XO-2S shows a positive correlation with the condensation temperatures of the elements, with a slope of $(4.7 \pm 0.9) \times 10^{-5}$ dex K$^{-1}$, which could mean that both components have not formed terrestrial planets, but that first experienced the accretion of rocky core interior to the subsequent giant planets., Comment: 10 pages, 5 figures, accepted by Astronomy & Astrophysics. Numbering of the series changed

Aims. We observed the $\tau$ Boo system with the HARPS-N spectrograph to test a new observational strategy aimed at jointly studying asteroseismology, the planetary orbit, and star-planet magnetic interaction. Methods. We collected high-cadence observations on 11 nearly consecutive nights and for each night averaged the raw FITS files using a dedicated software. In this way we obtained spectra with a high signal-to-noise ratio, used to study the variation of the CaII H&K lines and to have radial velocity values free from stellar oscillations, without losing the oscillations information. We developed a dedicated software to build a new custom mask that we used to refine the radial velocity determination with the HARPS-N pipeline and perform the spectroscopic analysis. Results. We updated the planetary ephemeris and showed the acceleration caused by the stellar binary companion. Our results on the stellar activity variation suggest the presence of a high-latitude plage during the time span of our observations. The correlation between the chromospheric activity and the planetary orbital phase remains unclear. Solar-like oscillations are detected in the radial velocity time series: we estimated asteroseismic quantities and found that they agree well with theoretical predictions. Our stellar model yields an age of $0.9\pm0.5$ Gyr for $\tau$ Boo and further constrains the value of the stellar mass to $1.38\pm0.05$ M$_\odot$., Comment: 14 pages, accepted for publication in Astronomy and Astrophysics

Young, nearby stars are ideal targets to search for planets using the direct imaging technique. The determination of stellar parameters is crucial for the interpretation of imaging survey results particularly since the luminosity of substellar objects has a strong dependence on system age. We have conducted a large program with NaCo at the VLT in order to search for planets and brown dwarfs in wide orbits around 86 stars. A large fraction of the targets observed with NaCo were poorly investigated in the literature. We performed a study to characterize the fundamental properties (age, distance, mass) of the stars in our sample. To improve target age determinations, we compiled and analyzed a complete set of age diagnostics. We measured spectroscopic parameters and age diagnostics using dedicated observations acquired with FEROS and CORALIE spectrographs at La Silla Observatory. We also made extensive use of archival spectroscopic data and results available in the literature. Additionally, we exploited photometric time-series, available in ASAS and Super-WASP archives, to derive rotation period for a large fraction of our program stars. We provided updated characterization of all the targets observed in the VLT NaCo Large program, a survey designed to probe the occurrence of exoplanets and brown dwarfs in wide orbits. The median distance and age of our program stars are 64 pc and 100 Myr, respectively. Nearly all the stars have masses between 0.70 and 1.50sun, with a median value of 1.01 Msun. The typical metallicity is close to solar, with a dispersion that is smaller than that of samples usually observed in radial velocity surveys. Several stars are confirmed or proposed here to be members of nearby young moving groups. Eight spectroscopic binaries are identified., Comment: 64 pages with Appendix, 15 figures, accepted to A&A