Search

© 2001 RAS. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. This research has made use the of the SIMBAD data base, operated at CDS, Strasbourg, France, and the ARI Database for Nearby Stars, Astronomisches Rechen-Institut, Heidelberg. We thank Dr D. Barrado y Navascués for providing us with some additional candidates to our initial sample of late-type stars. We also thank the anonymous referee for suggesting several improvements and helpful comments. This work was supported by the Universidad Complutense de Madrid and the Spanish Dirección General de Enseñanza Superior e Investigación Científica (DGESIC) under grant PB97-0259., This is the first paper of a series aimed at studying the properties of late-type members of young stellar kinematic groups. We concentrate our study on classical young moving groups such as the Local Association (Pleiades moving group, 20-150 Myr), IC 2391 supercluster (35 Myr), Ursa Major group (Sirius supercluster, 300 Myr), and Hyades supercluster (600 Myr), as well as on recently identified groups such as the Castor moving group (200 Myr). In this paper we compile a preliminary list of single late-type possible members of some of these young stellar kinematic groups. Stars are selected from previously established members of stellar kinematic groups based on photometric and kinematic properties as well as from candidates based on other criteria such as their level of chromospheric activity, rotation rate and lithium abundance. Precise measurements of proper motions and parallaxes taken from the Hipparcos Catalogue, as well as from the Tycho-2 Catalogue, and published radial velocity measurements are used to calculate the Galactic space motions (U, V W) and to apply Eggen's kinematic criteria in order to determine the membership of the selected stars to the different groups. Additional criteria using age-dating methods for late-type stars will be applied in forthcoming papers of this series. A further study of the list of stars compiled here could lead to a better understanding of the chromospheric activity and their age evolution, as well as of the star formation history in the solar neighbourhood. In addition, these stars are also potential search targets for direct imaging detection of substellar companions., Universidad Complutense de Madrid (UCM), Dirección General de Enseñanza Superior e Investigación Científica (DGESIC), España, Ministerio de Educación, Cultura y Deporte (MECD), España, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© ESO 2014. Artículo firmado por 36 autores. The authors are grateful to the referee for carefully reading the paper and for the useful remarks. This work was partly supported by the European Union FP7 program through ERC grant number 320360 and by the Leverhulme Trust through grant RPG-2012-541. We acknowledge the support from INAF and Ministero dell'Istruzione, dell' Universita e della Ricerca (MIUR) in the form of the grant "Premiale VLT 2012". The results presented here benefit from discussions held during the Gaia-ESO workshops and conferences supported by the ESF (European Science Foundation) through the GREAT Research Network Program. S.G.S. acknowledge the support from the Fundacao para a Ciencia e Tecnologia, FCT (Portugal) in the form of the fellowship SFRH/BPD/47611/2008. This research also made use of the SIMBAD database, operated at the CDS (Strasbourg, France) and of the Deep Near Infrared Survey of the Southern Sky (DENIS) database., One of the goals of the Gaia-ESO Survey (GES), which is conducted with FLAMES at the VLT, is the census and the characterization of the low-mass members of very young clusters and associations. We conduct a comparative study of the main properties of the sources belonging to gamma Velorum (gamma Vel) and Chamaeleon I (Cha I) young associations, focusing on their rotation, chromospheric radiative losses, and accretion. Methods. We used the fundamental parameters (effective temperature, surface gravity, lithium abundance, and radial velocity) delivered by the GES consortium in the first internal data release to select the members of gamma Vel and Cha I among the UVES and GIRAFFE spectroscopic observations. A total of 140 gamma Vel members and 74 Cha I members were studied. The procedure adopted by the GES to derive stellar fundamental parameters also provided measures of the projected rotational velocity (v sin i). We calculated stellar luminosities through spectral energy distributions, while stellar masses were derived by comparison with evolutionary tracks. The spectral subtraction of low-activity and slowly rotating templates, which are rotationally broadened to match the v sin i of the targets, enabled us to measure the equivalent widths (EWs) and the fluxes in the H alpha and H beta lines. The Ha line was also used for identifying accreting objects, on the basis of its EW and the width at the 10% of the line peak (10% W), and for evaluating the mass accretion rate ((M)over dot(acc)). Results. The distribution of v sin i for the members of. Vel displays a peak at about 10 km s(-1) with a tail toward faster rotators. There is also some indication of a different v sin i distribution for the members of its two kinematical populations. Most of these stars have Ha fluxes corresponding to a saturated activity regime. We find a similar distribution, but with a narrower peak, for Cha I. Only a handful of stars in gamma Vel display signatures of accretion, while many more, Unión Europea. FP7, Leverhulme Trust, INAF, Ministero dell'Istruzione, dell' Universita e della Ricerca (MIUR), ESF (European Science Foundation) through the GREAT Research Network Program, Fundacao para a Ciencia e Tecnologia, FCT (Portugal), Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© ESO 2010. Part of this work was co-supported by the Spanish MICINN, Ministerio de Ciencia e Innovación project numbers: AYA2008- 00695 and AYA2008-06423-C03-03. J. López Santiago is a postdoctoral fellow of the ASTROCAM (Red de Astrofísica en la CAM) with project number S-0505/ESP/000237 of the IV PRICIT Plan Regional de Investigación Científica e Innovación Tecnológica de la Comunidad de Madrid. The authors would like to thank the referee for useful comments and suggestions that allowed us to improve our work., Aims. We present a compilation of spectroscopic data from a survey of 144 chromospherically active young stars in the solar neighborhood, which may be used to investigate different aspects of its formation and evolution in terms of kinematics and stellar formation history. The data have already been used by us in several studies. With this paper, we make all these data accessible to the scientific community for future studies on different topics. Methods. We performed spectroscopic observations with echelle spectrographs to cover the entirety of the optical spectral range simultaneously. Standard data reduction was performed with the IRAF echelle package. We applied the spectral subtraction technique to reveal chromospheric emission in the stars of the sample. The equivalent width of chromospheric emission lines was measured in the subtracted spectra and then converted to fluxes using equivalent width-flux relationships. Radial and rotational velocities were determined by the cross-correlation technique. Kinematics, equivalent widths of the lithium line lambda 6707.8 angstrom and spectral types were also determined. Results. A catalog of spectroscopic data is compiled: radial and rotational velocities, space motion, equivalent widths of optical chromospheric activity indicators from Ca II H & K to the calcium infrared triplet and the lithium line in lambda 6708 angstrom. Fluxes in the chromospheric emission lines and R(HK)' are also determined for each observation of a star in the sample. We used these data to investigate the emission levels of our stars. The study of the Ha emission line revealed two different populations of chromospheric emitters in the sample, clearly separated in the log F(H alpha)/F(bol) - (V - J) diagram. The dichotomy may be associated with the age of the stars., Spanish MICINN, Ministerio de Ciencia e Innovación, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© ESO, 2010. Based on observations made with the 2.2 m telescope at the Centro Astronómico Hispano Alemán (CAHA) at Calar Alto (Spain) and the Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Istituto Nazionale de Astrofisica Italiano (INAF), in the Spanish Observatorio del Roque de los Muchachos. This research has been supported by the Programa de Acceso a Infraestructuras Científicas y Tecnológicas Singulares (ICTS). R. Martínez-Arnáiz acknowledges support from the Spanish Ministerio de Educación y Ciencia (currently the Ministerio de Ciencia e Innovación), under the grant FPI20061465-00592 (Programa Nacional Formación Personal Investigador) and projects AYA2008-00695 (Programa Nacional de Astronomía y Astrofísica), AYA2008-01727 (Programa Nacional de Astronomía y Astrofísica), AstroMadrid S2009/ESP-1496. This research has made use of the SIMBAD database and VizieR catalogue access tool, operated at CDS, Strasbourg, France. We also thank the anonymous referee for his/her valuable suggestions on how to improve the manuscript., Context. Chromospheric activity produces both photometric and spectroscopic variations that can be mistaken as planets. Large spots crossing the stellar disc can produce planet-like periodic variations in the light curve of a star. These spots clearly affect the spectral line profiles, and their perturbations alter the line centroids creating a radial velocity jitter that might “contaminate” the variations induced by a planet. Precise chromospheric activity measurements are needed to estimate the activity-induced noise that should be expected for a given star. Aims. We obtain precise chromospheric activity measurements and projected rotational velocities for nearby (d ≤ 25 pc) cool (spectral types F to K) stars, to estimate their expected activity-related jitter. As a complementary objective, we attempt to obtain relationships between fluxes in different activity indicator lines, that permit a transformation of traditional activity indicators, i.e., Ca II H & K lines, to others that hold noteworthy advantages. Methods. We used high resolution (~50 000) echelle optical spectra. Standard data reduction was performed using the IRAF ECHELLE package. To determine the chromospheric emission of the stars in the sample, we used the spectral subtraction technique. We measured the equivalent widths of the chromospheric emission lines in the subtracted spectrum and transformed them into fluxes by applying empirical equivalent width and flux relationships. Rotational velocities were determined using the cross-correlation technique. To infer activity-related radial velocity (RV) jitter, we used empirical relationships between this jitter and the R’_HK index. Results. We measured chromospheric activity, as given by different indicators throughout the optical spectra, and projected rotational velocities for 371 nearby cool stars. We have built empirical relationships among the most important chromospheric emission lines. Finally, we used the measured chromospheric activity to esti, Ministerio de Ciencia e Innovación (MICINN), Ministerio de Economía y Competitividad (MINECO), Comunidad de Madrid, Plan Nacional de I+D+i (MINECO), Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2015. The American Astronomical Society. All rights reserved. This research made use of SIMBAD, operated at Centre de Données astronomiques de Strasbourg, France, and NASA's Astrophysics Data System. Financial support was provided by the Spanish Ministerio de Ciencia e Innovación and Ministerio de Economía y Competitividad under grants AYA2010-17631, AYA2010-15081, AYA2010-21697-C05-04, AYA2011-30147-C03-03, AYA2012-39364-C02-01/02, and Severo Ochoa SEV-2011-0187, and by the Canary Islands Government under grant PID2010119. R.H.B. acknowledges support from FONDECYT Regular project 1140076. J.S.-B. acknowledges support by the JAE-PreDoc program of the Spanish Consejo Superior de Investigaciones Científicas (CSIC). A.S. acknowledges support by the Janos Bolyai Research Scholarship of the Hungarian Academy of Sciences. We acknowledge F. Najarro, J. Puls, A. Herrero, J. Casares, and H. Blau for interesting discussions during the development of this paper and their useful comments on one of the latest drafts before submission. We thank G. Schaefer for providing us some information about the results from the analysis of the interferometric observations prior to publication. Lastly, we thank the anonymous referee for a very professional report that helped us to improve the first version of the manuscript. Based on observations made with the Nordic Optical Telescope, operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofísica de Canarias. Based on observations made with the Mercator Telescope, operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. Based on observations obtained with the HERMES spectrograph, which is supported by the Fund for Scientific Research of Flanders (FWO), Belgium, the Research Council of K.U. Leuven, Belgium, the Fonds National de la Recherche, We provide a complete characterization of the astrophysical properties of the sigma Ori Aa, Ab, B hierarchical triple system and an improved set of orbital parameters for the highly eccentric sigma Ori Aa, Ab spectroscopic binary. We compiled a spectroscopic data set comprising 90 high-resolution spectra covering a total time span of 1963 days. We applied the Lehman-Filhes method for a detailed orbital analysis of the radial velocity curves and performed a combined quantitative spectroscopic analysis of the sigma Ori Aa, Ab, B system by means of the stellar atmosphere code FASTWIND. We used our own plus other available information on photometry and distance to the system for measuring the radii, luminosities, and spectroscopic masses of the three components. We also inferred evolutionary masses and stellar ages using the Bayesian code BONNSAI. The orbital analysis of the new radial velocity curves led to a very accurate orbital solution of the sigma Ori Aa, Ab pair. We provided indirect arguments indicating that sigma Ori B is a fast-rotating early B dwarf. The FASTWIND+BONNSAI analysis showed that the Aa, Ab pair contains the hottest and most massive components of the triple system while sigma Ori B is a bit cooler and less massive. The derived stellar ages of the inner pair are intriguingly younger than the one widely accepted for the sigma Orionis cluster, at 3 +/- 1 Ma. The outcome of this study will be of key importance for a precise determination of the distance to the s Orionis cluster, the interpretation of the strong X-ray emission detected for sigma Ori Aa, Ab, B, and the investigation of the formation and evolution of multiple massive stellar systems and substellar objects., Spanish Ministerio de Ciencia e Innovación, Ministerio de Economía y Competitividad, Severo Ochoa, Canary Islands Government, FONDECYT Regular project, JAE-PreDoc program of the Spanish Consejo Superior de Investigaciones Científicas (CSIC), Janos Bolyai Research Scholarship of the Hungarian Academy of Sciences, Fund for Scientific Research of Flanders (FWO), Belgium, Research Council of K.U. Leuven, Belgium, Fonds National de la Recherche Scientifique (F.R.S.-FNRS), Belgium, Royal Observatory of Belgium, Observatoire de Genève, Switzerland, Thringer Landessternwarte Tautenburg, Germany, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© 2015. The American Astronomical Society. All rights reserved. This research was partially supported by grant AYA2011-29754-C03-01 from the Government of Spain., In this work, we identify 63 bona fide new candidates to T Tauri stars (TTSs) in the Taurus-Auriga region, using its ultraviolet excess as our baseline. The initial data set was defined from the GALEX all sky survey (AIS). The GALEX satellite obtained images in the near-ultraviolet (NUV) and far-ultraviolet (FUV) bands where TTSs show a prominent excess compared with main-sequence or giants stars. GALEX AIS surveyed the Taurus-Auriga molecular complex, as well as a fraction of the California Nebula and the Perseus complex; bright sources and dark clouds were avoided. The properties of TTSs in the ultraviolet (GALEX), optical (UCAC4), and infrared (2MASS) have been defined using the TTSs observed with the International Ultraviolet Explorer reference sample. The candidates were identified by means of a mixed ultraviolet-optical-infrared excess set of colors; we found that the FUV-NUV versus J-K color-color diagram is ideally suited for this purpose. From an initial sample of 163,313 bona fide NUV sources, a final list of 63 new candidates to TTSs in the region was produced. The search procedure has been validated by its ability to detect all known TTSs in the area surveyed: 31 TTSs. Also, we show that the weak-lined TTSs are located in a well-defined stripe in the FUV-NUV versus J-K diagram. Moreover, in this work, we provide a list of TTSs photometric standards for future GALEX-based studies of the young stellar population in star forming regions., Government of Spain, Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

©ESO 2021. Artículo firmado por 20 autores. We thank an anonymous referee for helpful comments that improved the quality of this paper. CARMENES is an instrument for the Centro Astronómico Hispano-Alemán de Calar Alto (CAHA, Almeria, Spain). CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Científicas (CSIC), European Regional Development Fund (ERDF) through projects FICTS-201102, ICTS-2017-07-CAHA-4, and CAHA16-CE-3978, and the members of the CARMENES Consortium (Max-Planck-Institut fur Astronomie, Instituto de Astrofísica de Andalucía, Landessternwarte Konigstuhl, Institut de Ciencies de l'Espai, Insitut fur Astrophysik Gottingen, Universidad Complutense de Madrid, Thuringer Landessternwarte Tautenburg, Instituto de Astrofísica de Canarias, Hamburger Sternwarte, Centro de Astrobiología and Centro Astronómico Hispano-Alemán), with additional contributions by the Spanish Ministry of Economy, the German Science Foundation through the Major Research Instrumentation Programme and DFG Research Unit FOR2544 "Blue Planets around Red Stars", the Klaus Tschira Stiftung, the states of Baden-Wurttemberg and Niedersachsen, and by the Junta de Andalucía. E.D.M. and A.A.K. acknowledge the support by the Investigador FCT contract IF/00849/2015/CP1273/CT0003. We acknowledge financial support from NASA through grant NNX17AG24G, the Agencia Estatal de Investigación of the Ministerio de Ciencia through fellowship FPU15/01476, Innovación y Universidades and the ERDF through projects PID2019-109522GB-C51/2/3/4, AYA2016-79425-C3-1/2/3-P and AYA2018-84089, the Fundacao para a Ciencia e a Tecnologia through and ERDF through grants UID/FIS/04434/2019, UIDB/04434/2020 and UIDP/04434/2020, PTDC/FIS-AST/28953/2017, and PTDC/FIS-AST/32113/2017, and COMPETE2020 -Programa Operacional Competitividade e Internacionalizacao POCI-01-0145-FEDER-028953, and POCI01-0145-FEDER-032113. This research has been funded by the Spanish State Resear, Deriving metallicities for solar-like stars follows well-established methods, but for cooler stars such as M dwarfs, the determination is much more complicated due to forests of molecular lines that are present. Several methods have been developed in recent years to determine accurate stellar parameters for these cool stars (T-eff less than or similar to 4000 K). However, significant differences can be found at times when comparing metallicities for the same star derived using different methods. In this work, we determine the effective temperatures, surface gravities, and metallicities of 18 well-studied M dwarfs observed with the CARMENES high-resolution spectrograph following different approaches, including synthetic spectral fitting, analysis of pseudo-equivalent widths, and machine learning. We analyzed the discrepancies in the derived stellar parameters, including metallicity, in several analysis runs. Our goal is to minimize these discrepancies and find stellar parameters that are more consistent with the literature values. We attempted to achieve this consistency by standardizing the most commonly used components, such as wavelength ranges, synthetic model spectra, continuum normalization methods, and stellar parameters. We conclude that although such modifications work quite well for hotter main-sequence stars, they do not improve the consistency in stellar parameters for M dwarfs, leading to mean deviations of around 50-200 K in temperature and 0.1-0.3 dex in metallicity. In particular, M dwarfs are much more complex and a standardization of the aforementioned components cannot be considered as a straightforward recipe for bringing consistency to the derived parameters. Further in-depth investigations of the employed methods would be necessary in order to identify and correct for the discrepancies that remain., Ministerio de Ciencia e Innovación (MICINN)/FEDER, Unidad de Excelencia María de Maeztu, Ministerio de Ciencia e Innovación (MICINN), Max Planck Society, Consejo Superior de Investigaciones Científicas (CSIC), Investigador FCT contract, NASA National Aeronautics & Space Administration (NASA), Fundacao para a Ciencia e a Tecnologia Portuguese Foundation for Science and Technology European Commission, COMPETE2020 -Programa Operacional Competitividade e Internacionalizacao, Spanish State Research Agency (AEI) Spanish Government, Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

© ESO 2022. Artículo firmado por 27 autores. We thank E. Martín for his fruitful comments as referee of this paper. Based on data products from observations made with ESO Telescopes at the La Silla Paranal Observatory under programmes 188.B-3002, 193.B-0936, and 197.B-1074. These data products have been processed by the Cambridge Astronomy Survey Unit (CASU) at the Institute of Astronomy, University of Cambridge, and by the FLAMES/UVES reduction team at INAF/Osservatorio Astrofisico di Arcetri. These data have been obtained from the Gaia-ESO Survey Data Archive, prepared and hosted by the Wide Field Astronomy Unit, Institute for Astronomy, University of Edinburgh, which is funded by the UK Science and Technology Facilities Council. This work was partly supported by the European Union FP7 programme through ERC grant number 320360 and by the Leverhulme Trust through grant RPG-2012-541. We acknowledge the support from INAF and Ministero dell'Istruzione, dell'Universita e della Ricerca (MIUR) in the form of the grant "Premiale VLT 2012". The results presented here benefit from discussions held during the Gaia ESO workshops and conferences supported by the ESF (European Science Foundation) through the GREAT Research Network Programme. We acknowledge the support from INAF in the form of the grant for mainstream projects "Enhancing the legacy of the Gaia-ESO Survey for open clusters science". E.T. acknowledges Czech Science Foundation GAC. R (Project: 21-16583M) and the "visiting fellow program" of the University of Pisa. P.G.P.M. and S.D. acknowledge INFN (Iniziativa specifica TAsP). E.P. and N.S. acknowledge financial support from Progetto Main Stream INAF "Chemo-dynamics of globular clusters: the Gaia revolution". R.B. acknowledges financial support from the project PRININAF 2019 "Spectroscopically Tracing the Disk Dispersal Evolution". F.J.E. acknowledges financial support from the Spanish MINECO/FEDER through the grant AYA2017-84089 and MDM-2017-0737 at Centro de Astr, Context. It is now well-known that pre-main-sequence models with inflated radii should be taken into account to simultaneously reproduce the colour-magnitude diagram and the lithium depletion pattern observed in young open star clusters. Aims. We tested a new set of pre-main-sequence models that include radius inflation due to the presence of starspots or to magnetic inhibition of convection. We used five clusters observed by the Gaia-ESO Survey that span the age range similar to 10-100 Myr, in which these effects could be important. Methods. The Gaia-ESO Survey radial velocities were combined with astrometry from Gaia EDR3 to obtain clean lists of high-probability members for the five clusters. A Bayesian maximum likelihood method was adopted to fit the observed cluster sequences to theoretical predictions to derive the best model parameters and the cluster reddening and age. Models were calculated with different values of the mixing length parameter (alpha(ML) = 2.0, 1.5 and 1.0) for the cases without spots or with effective spot coverage beta(spot) = 0.2 and 0.4. The models were also compared with the observed lithium depletion patterns. Results. To reproduce the colour-magnitude diagram and the observed lithium depletion pattern in Gamma Vel A and B and in 25 Ori, both a reduced convection efficiency, with alpha(ML) = 1.0, and an effective surface spot coverage of about 20% are required. We obtained ages of 18(-4.0)(+1.5) - Myr and 21(-3.0)(+3.5)Myr for Gamma Vel A and B, respectively, and 19(-7.0)(+1.5) 19(-7.0+)(1.5) Myr for 25 Ori. However, a single isochrone is not sufficient to account for the lithium dispersion, and an increasing level of spot coverage as mass decreases seems to be required. On the other hand, the older clusters (NGC 2451 B at 30(-5.0)(3.0) Myr, NGC 2547 at 35(-4.0)(+4.0) Myr, and NGC 2516 at 138(-42)(+48) Myr) are consistent with standard models (i.e. alpha(ML) = 2.0 and no spots) except at low masses: a 20% sp, Unión Europea. Horizonte 2020, Unión Europea. FP7, Ministerio de Economía y Competitividad (MINECO)/FEDER, Unidad de Excelencia María de Maeztu, ESO Telescopes at the La Silla Paranal Observatory under programmes, UK Science and Technology Facilities Council UK Research & Innovation (UKRI) Science & Technology Facilities Council (STFC), Leverhulme TrustLeverhulme Trust, Istituto Nazionale Astrofisica (INAF), Ministero dell'Istruzione, dell'Universita e della Ricerca (MIUR) Ministry of Education, Universities and Research (MIUR), ESF (European Science Foundation) through the GREAT Research Network Programme, INAF in the form of the grant for mainstream projects "Enhancing the legacy of the Gaia-ESO Survey for open clusters science”, Czech Science Foundation GAC, University of Pisa, INFN (Iniziativa specifica TAsP), Progetto Main Stream INAF "Chemo-dynamics of globular clusters: the Gaia revolution", Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

We present the wide field slitless spectroscopy mode of the NIRISS instrument on the James Webb Space Telescope. This mode employs two orthogonal low-resolution (resolving power approximate to 150) grisms in combination with a set of six blocking filters in the wavelength range 0.8-2.3 mu m to provide a spectrum of almost every source across the field-of-view. When combined with the low background, high sensitivity and high spatial resolution afforded by the telescope, this mode will enable unprecedented studies of the structure and evolution of distant galaxies. We describe the performance of the as-built hardware relevant to this mode and expected imaging and spectroscopic sensitivity. We discuss operational and calibration procedures to obtain the highest quality data. As examples of the observing mode usage, we present details of two planned Guaranteed Time Observations programs: The Canadian NIRISS Unbiased Cluster Survey and The NIRISS Survey for Young Brown Dwarfs and Rogue Planets.

© ESO 2021. Artículo firmado por 27 autores. We thank the anonymous referee for the insightful comments and suggestions that improved the manuscript of the paper. CARMENES is an instrument for the Centro Astronómico Hispano en Andalucía at Calar Alto (CAHA). CARMENES is funded by the German Max-Plank Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Científicas (CSIC), the European Union through FEDER/ERF FICTS-2011-02 funds, and the members of the CARMENES Consortium (Max-Plank-Institut fur Astronomie, Instituto de Astrofísica de Andalucía, Landessternwarte Konigstuhl, Institut de Ciences de l'Espai, Institut fur Astrophysik Gottingen, Universidad Complutense de Madrid, Thuringer Landessternwarte Tautenberg, Instituto de Astrofísica de Canarias, Hamburger Sternwarte, Centro de Astrobiología and Centro Astronómico Hispano-Andaluz), with additional contributions by the Spanish Ministry of Economy, the German Science Foundation through the Major Research Instrumentation Programme and DFG Research Unit FOR2544 "Blue Planets around Red Stars", the Klaus Tschira Stiftung, the states of BadenWurttemberg and Niedersachsen, and by the Junta de Andalucía. The authors acknowledge financial support from the Fundacao para a Ciencia e a Tecnologia (FCT) through the research grants UID/FIS/04434/2019, UIDB/04434/2020 and UIDP/04434/2020, national funds PTDC/FIS-AST/28953/2017, by FEDER (Fundo Europeu de Desenvolvimento Regional) through COMPETE2020 Programa Operacional Competitividade e Internacionalizacao (POCI-01-0145FEDER-028953), and the Spanish Ministerio de Ciencia, Innovación y Universidades, Ministerio de Economía y Competitividad, the Universidad Complutense de Madrid, and the Fondo Europeo de Desarrollo Regional (FEDER/ERF) through fellowship FPU15/01476, and projects AYA2016-79425-C3-1/2/3-P, PID2019-109522GB-C5[1:4]/AEI/10.13039/501100011033, AYA2014-56359-P, BES-2017-080769, and RYC-2013-14875. The authors also acknowledge financial support from the, We determined effective temperatures, surface gravities, and metallicities for a sample of 343 M dwarfs observed with CARMENES, the double-channel, high-resolution spectrograph installed at the 3.5 m telescope at Calar Alto Observatory. We employed STEPARSYN, a Bayesian spectral synthesis implementation particularly designed to infer the stellar atmospheric parameters of late-type stars following a Markov chain Monte Carlo approach. We made use of the BT-Settl model atmospheres and the radiative transfer code turbospectrum to compute a grid of synthetic spectra around 75 magnetically insensitive Fel and Til lines plus the TiO gamma and epsilon bands. To avoid any potential degeneracy in the parameter space, we imposed Bayesian priors on T-eff and log g based on the comprehensive, multi-band photometric data available for the sample. We find that this methodology is suitable down to M7.0 V, where refractory metals such as Ti are expected to condense in the stellar photospheres. The derived Teff, log g, and [Fe/H] range from 3000 to 4200 K, 4.5 to 5.3 dex, and -0.7 to 0.2 dex, respectively. Although our T (eff) scale is in good agreement with the literature, we report large discrepancies in the [Fe/H] scales, which might arise from the different methodologies and sets of lines considered. However, our [Fe/H] is in agreement with the metallicity distribution of FGK-type stars in the solar neighbourhood and correlates well with the kinematic membership of the targets in the Galactic populations. Lastly, excellent agreement in T (eff) is found for M dwarfs with interferometric angular diameter measurements, as well as in the [Fe/H] between the components in the wide physical FGK+M and M+M systems included in our sample., Ministerio de Economía y Competitividad (MINECO)/FEDER, Ministerio de Ciencia e Innovación (MICINN)/FEDER, German Max-Plank Gesellschaft (MPG), Centro de Excelencia Severo Ochoa, Unidad de Excelencia María de Maeztu, Consejo Superior de Investigaciones Cientificas (CSIC), German Science Foundation through the Major Research Instrumentation Programme, Klaus Tschira Stiftung, State of Baden-Wurttemberg, State of Niedersachsen, Junta de Andalucía, Fundacao para a Ciencia e a Tecnologia (FCT) Portuguese Foundation for Science and Technology European Commission, FEDER (Fundo Europeu de Desenvolvimento Regional) through COMPETE2020 Programa Operacional Competitividade e Internacionalizacao, Ministerio de Ciencia, Innovación y Universidades, Universidad Complutense de Madrid, Instituto de Astrofísica de Andalucía, Centro de Astrobiología, Generalitat de Catalunya/CERCA programme, DPAC, NASA National Aeronautics & Space Administration, DFG priority program SPP 1992 "Exploring the Diversity of Extrasolar Planets" German Research Foundation (DFG), Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub

© ESO 2021. This publication makes use of VOSA, developed under the Spanish Virtual Observatory project supported by the Spanish MINECO through grant AYA2017-84089. VOSA has been partially updated by using funding from the European Union’s Horizon 2020 Research and Innovation Programme, under Grant Agreement 776403 (EXOPLANETS-A) . NL wasfunded by the Spanish Ministry of Economy and Competitiveness (MINECO) through programme number AYA2015-69350-C3-2-P. ZHZ is supported by the Fundamental Research Funds for the Central Universities (Grant No.14380034). This work is based on observations made with the William Herschel telescope (programme C95; PI Galvez-Ortiz) operated on the island of La Palma by the Isaac Newton Group of Telescopes in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. The data presented here were obtained with ALFOSC, which is provided by the Instituto de Astrofísica de Andalucía (IAA) under a joint agreement with the University of Copenhagen and NOTSA. This research has made use of the Simbad and Vizier databases, operated at the centre de Données Astronomiques de Strasbourg (CDS), and of NASA’s Astrophysics Data System Bibliographic Services(ADS). This research has also made use of some of the tools developed as part of the Virtual Observatory. 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. Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation, the U.S. Department of Energy Office of Science, and the Participating Institutions. SDSS-IV acknowledges support and resources from the Center for High-Performance Computing at the Unive, Aims: The aim of the project is to identify wide common proper motion companions to a sample of spectroscopically confirmed M and L metal-poor dwarfs (also known as subdwarfs) to investigate the impact of metallicity on the binary fraction of low-mass metal-poor binaries and to improve the determination of their metallicity from the higher-mass binary. Methods. We made use of Virtual Observatory tools and large-scale public surveys to look in Gaia for common proper motion companions to a well-defined sample of ultracool subdwarfs with spectral types later than M5 and metallicities below or equal to −0.5 dex. We collected low-resolution optical spectroscopy for our best system, which is a binary composed of one sdM1.5 subdwarf and one sdM5.5 subdwarf located at ∼1 360 au, and for another two likely systems separated by more than 115 000 au. Results. We confirm one wide companion to an M subdwarf, and infer a multiplicity for M subdwarfs (sdMs) of 1.0^(+2.0)_(−1.0) % for projected physical separations of up to 743 000 au. We also find four M–L systems, three of which are new detections. No colder companion was identified in any of the 219 M and L subdwarfs of the sample, mainly because of limitations on the detection of faint sources with Gaia. We infer a frequency of wide systems for sdM5–9.5 of 0.60^(+1.17)_(−0.60)% for projected physical separations larger than 1 360 au (up to 142 400 au). This study shows a multiplicity rate of 1.0^(+2.0)_(−1.0)% in sdMs, and 1.9^(+3.7)_(−1.9)% in extreme M subdwarfs (esdMs). We did not find any companion for the ultra M subdwarfs (usdMs) of our sample, establishing an upper limit of 5.3% on binarity for these objects., Unión Europea. Horizonte 2020, Ministerio de Economía y Competitividad (MINECO), España. Ministerio de Economía y Competitividad (MINECO), Fundamental Research Funds, Instituto de Astrofisica de Andalucia (IAA), Alfred P. Sloan Foundation, United States Department of Energy (DOE), Center for High-Performance Computing at the University of Utah, Brazilian Participation Group, Carnegie Institution for Science, Carnegie Mellon University, Chilean Participation Group, French Participation Group, Smithsonian Institution Harvard-Smithsonian Center for Astrophysics, Instituto de Astrofisica de Canarias, Johns Hopkins University, Kavli Institute for the Physics and Mathematics of the Universe (IPMU)/University of Tokyo, United States Department of Energy (DOE), Leibniz Institut fur Astrophysik Potsdam (AIP), Max-Planck-Institut fur Astronomie (MPIA Heidelberg), Max-Planck-Institut fur Astrophysik (MPA Garching), Max-Planck-Institut fur Extraterrestrische Physik (MPE), National Astronomical Observatories of China, New Mexico State University, New York University, University of Notre Dame, Observatario Nacional/MCTI, Ohio State University, Pennsylvania State University, Shanghai Astronomical Observatory, United Kingdom Participation Group, Universidad Nacional Autonoma de Mexico, University of Arizona, University of Colorado Boulder, University of Oxford, University of Portsmouth, University of Utah, University of Virginia, University of Washington, University of Wisconsin, Vanderbilt University, Yale University, National Aeronautics & Space Administration (NASA), National Science Foundation (NSF), Depto. de Física de la Tierra y Astrofísica, Fac. de Ciencias Físicas, TRUE, pub