127 research outputs found

    CARMENES detection of the Ca II infrared triplet and possible evidence of He I in the atmosphere of WASP-76b

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    Casasayas-Barris, N., et al.Ultra-hot Jupiters are highly irradiated gas giants with equilibrium temperatures typically higher than 2000 K. Atmospheric studies of these planets have shown that their transmission spectra are rich in metal lines, with some of these metals being ionised due to the extreme temperatures. Here, we use two transit observations of WASP-76b obtained with the CARMENES spectrograph to study the atmosphere of this planet using high-resolution transmission spectroscopy. Taking advantage of the two channels and the coverage of the red and near-infrared wavelength ranges by CARMENES, we focus our analysis on the study of the Ca II infrared triplet (IRT) at 8500 Å and the He I triplet at 10 830 Å. We present the discovery of the Ca II IRT at 7¿ in the atmosphere of WASP-76b using the cross-correlation technique, which is consistent with previous detections of the Ca II H&K lines in the same planet, and with the atmospheric studies of other ultra-hot Jupiters reported to date. The low mass density of the planet, and our calculations of the XUV (X-ray and EUV) irradiation received by the exoplanet, show that this planet is a potential candidate to have a He I evaporating envelope and, therefore, we performed further investigations focussed on this aspect. The transmission spectrum around the He I triplet shows a broad and red-shifted absorption signal in both transit observations. However, due to the strong telluric contamination around the He I lines and the relatively low signal-to-noise ratio of the observations, we are not able to unambiguously conclude if the absorption is due to the presence of helium in the atmosphere of WASP-76b, and we consider the result to be only an upper limit. Finally, we revisit the transmission spectrum around other lines such as Na I, Li I, H¿, and K I. The upper limits reported here for these lines are consistent with previous studies.We acknowledge funding from the European Research Council under the European Union’s Horizon 2020 research and innovation program under grant agreement no. 694513, the Agencia Estatal de Investigación of the Ministerio de Ciencia, Innovación y Universidades and the ERDF through projects PID2019-109522GB-C5[1:4]/AEI/10.13039/501100011033, PID2019- 110689RB-I00/AEI/10.13039/501100011033, ESP2017-87143-R, and ESP2016- 80435-C2-2-R, and the Centre of Excellence “Severo Ochoa” and “María de Maeztu” awards to the Instituto de Astrofísica de Canarias (CEX2019-000920- S), Instituto de Astrofísica de Andalucía (SEV-2017-0709), and Centro de Astrobiología (MDM-2017-0737), and the Generalitat de Catalunya/CERCA programme. T.H. acknowledges support by the European Research Council under the Horizon 2020 Framework Program via the ERC Advanced Grant Origins 83 24 28. G.M. has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie SkƂodowska-Curie grant agreement No. 895525

    BiologĂ­a molecular de la asimilaciĂłn de nitrato en algas

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    El alga verde eucariótica Chlamydomonas reinhardtii es un organismo modelo para el estudio de la biología molecular de la asimilación de nitrato. Este sistema biológico presenta excelentes cualidades para estudios bioquímicos, fisiológicos, genéticos y moleculares. Estas investigaciones han permitido los siguientes logros: i) generación de una colección de mutantes; ii) identificación y caracterización de genes para el transporte de amonio; iii) caracterización de genes del transporte biespecífico de bicarbonato/nitrito; iv) clonación y caracterización del gen que codifica la proteína portadora de cofactor de molibdeno (MCP), determinación de la estructura cristalina de la misma y de sus residuos funcionales en la unión del cofactor; v) utilización de una nueva estrategia para identificar mutantes del cofactor de molibdeno; y vi) identificación de un nuevo LTR-retrotransposón de la familia gypsy

    A detailed analysis of the Gl 486 planetary system

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    Full list of authors: Caballero, J. A.; Gonzalez-Alvarez, E.; Brady, M.; Trifonov, T.; Ellis, T. G.; Dorn, C.; Cifuentes, C.; Molaverdikhani, K.; Bean, J. L.; Boyajian, T.; Rodriguez, E.; Sanz-Forcada, J.; Zapatero Osorio, M. R.; Abia, C.; Amado, P. J.; Anugu, N.; Bejar, V. J. S.; Davies, C. L.; Dreizler, S.; Dubois, F.; Ennis, J.; Espinoza, N.; Farrington, C. D.; Garcia Lopez, A.; Gardner, T.; Hatzes, A. P.; Henning, Th; Herrero, E.; Herrero-Cisneros, E.; Kaminski, A.; Kasper, D.; Klement, R.; Kraus, S.; Labdon, A.; Lanthermann, C.; Le Bouquin, J-B; Lopez Gonzalez, M. J.; Luque, R.; Mann, A. W.; Marfil, E.; Monnier, J. D.; Montes, D.; Morales, J. C.; Palle, E.; Pedraz, S.; Quirrenbach, A.; Reffert, S.; Reiners, A.; Ribas, I; Rodriguez-Lopez, C.; Schaefer, G.; Schweitzer, A.; Seifahrt, A.; Setterholm, B. R.; Shan, Y.; Shulyak, D.; Solano, E.; Sreenivas, K. R.; Stefansson, G.; Stuermer, J.; Tabernero, H. M.; Tal-Or, L.; ten Brummelaar, T.; Vanaverbeke, S.; von Braun, K.; Youngblood, A.; Zechmeister, M.- This is an Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.Context. The Gl 486 system consists of a very nearby, relatively bright, weakly active M3.5 V star at just 8 pc with a warm transiting rocky planet of about 1.3 R⊕ and 3.0 M⊕. It is ideal for both transmission and emission spectroscopy and for testing interior models of telluric planets. Aims. To prepare for future studies, we aim to thoroughly characterise the planetary system with new accurate and precise data collected with state-of-the-art photometers from space and spectrometers and interferometers from the ground. Methods. We collected light curves of seven new transits observed with the CHEOPS space mission and new radial velocities obtained with MAROON-X at the 8.1 m Gemini North telescope and CARMENES at the 3.5 m Calar Alto telescope, together with previously published spectroscopic and photometric data from the two spectrographs and TESS. We also performed near-infrared interferometric observations with the CHARA Array and new photometric monitoring with a suite of smaller telescopes (AstroLAB, LCOGT, OSN, TJO). This extraordinary and rich data set was the input for our comprehensive analysis. Results. From interferometry, we measure a limb-darkened disc angular size of the star Gl 486 at ΞLDD = 0.390 ± 0.018 mas. Together with a corrected Gaia EDR3 parallax, we obtain a stellar radius R* = 0.339 ± 0.015 R⊕. We also measure a stellar rotation period at Prot = 49.9 ± 5.5 days, an upper limit to its XUV (5-920 A) flux informed by new Hubble/STIS data, and, for the first time, a variety of element abundances (Fe, Mg, Si, V, Sr, Zr, Rb) and C/O ratio. Moreover, we imposed restrictive constraints on the presence of additional components, either stellar or sub-stellar, in the system. With the input stellar parameters and the radial-velocity and transit data, we determine the radius and mass of the planet Gl 486 b at Rp = 1.343−0.062+0.063 R⊕ and Mp = 3.00−0.12+0.13 M⊕, with relative uncertainties of the planet radius and mass of 4.7% and 4.2%, respectively. From the planet parameters and the stellar element abundances, we infer the most probable models of planet internal structure and composition, which are consistent with a relatively small metallic core with respect to the Earth, a deep silicate mantle, and a thin volatile upper layer. With all these ingredients, we outline prospects for Gl 486 b atmospheric studies, especially with forthcoming James Webb Space Telescope (Webb) observations. © J. A. Caballero et al. 2022.CARMENES is an instrument at the Centro AstronĂłmico Hispano en AndalucĂ­a (CAHA) at Calar Alto (AlmerĂ­a, Spain), operated jointly by the Junta de AndalucĂ­a and the Instituto de AstrofĂ­sica de AndalucĂ­a (CSIC). CARMENES was funded by the Max-Planck-Gesellschaft (MPG), the Consejo Superior de Investigaciones CientĂ­ficas (CSIC), the Ministerio de EconomĂ­a y Competitividad (MINECO) and the European Regional Development Fund (ERDF) through projects FICTS-2011-02, ICTS-2017-07-CAHA-4, and CAHA16-CE-3978, and the members of the CARMENES Consortium (Max-Planck-Institut fĂŒr Astronomie, Instituto de AstrofĂ­sica de AndalucĂ­a, Landessternwarte Königstuhl, Institut de CiĂšncies de l’Espai, Institut fĂŒr Astrophysik Göttingen, Universidad Complutense de Madrid, ThĂŒringer Landessternwarte Tautenburg, Instituto de AstrofĂ­sica de Canarias, Hamburger Sternwarte, Centro de AstrobiologĂ­a and Centro AstronĂłmico Hispano-AlemĂĄn), with additional contributions by the MINECO, the Deutsche Forschungsgemeinschaft (DFG) through the Major Research Instrumentation Programme and Research Unit FOR2544 “Blue Planets around Red Stars”, the Klaus Tschira Stiftung, the states of Baden-WĂŒrttemberg and Niedersachsen, and by the Junta de AndalucĂ­a. This work is based upon observations obtained with the Georgia State University (GSU) Center for High Angular Resolution Astronomy Array at Mount Wilson Observatory. The CHARA Array is supported by the National Science Foundation under Grant No. AST-1636624 and AST-2034336. Institutional support has been provided from the GSU College of Arts and Sciences and the GSU Office of the Vice President for Research and Economic Development. We would like to recognise the observing team, scientists, and support staff at the CHARA Array. Observation time for this work was generously allocated via discretionary time from CHARA Array director Theo ten Brumelaar and via NOIRLab community access program (proposals 2021A-0247 and 2021A-0141). MIRC-X received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant No. 639889), as well as from NASA (XRP NNX16AD43G) and NSF (AST 1909165). Data were partly collected with the 90 cm telescope at the Observatorio de Sierra Nevada operated by the Instituto de AstrofĂ­fica de AndalucĂ­a (IAA-CSIC). This work made use of observations from the Las Cumbres Observatory Global Telescope network. LCOGT observations were partially acquired via program number TAU2021A-015 of the Wise Observatory, Tel-Aviv University, Israel. We acknowledge financial support from the Agencia Estatal de InvestigaciĂłn of the Ministerio de Ciencia, InnovaciĂłn y Universidades and the ERDF through projects PID2019-109522GB-C5[1:4], PID2019-107061GB-C64, PID2019-110689RB-100, PGC2018-095317-B-C21, PGC2018-102108-B-I00, and the Centre of Excellence “Severo Ochoa” and “MarĂ­a de Maeztu” awards to the Instituto de AstrofĂ­sica de Canarias (CEX2019-000920-S), Instituto de AstrofĂ­sica de AndalucĂ­a (SEV-2017-0709), and Centro de AstrobiologĂ­a (MDM-2017-0737), DFG through FOR2544 (KU 3625/2-1) and Germany’s Excellence Strategy to the Excellence Cluster ORIGINS (EXC-2094 - 390783311), European Research Council (Starting Grant 639889), Bulgarian National Science Fund through VIHREN-2021 (KP-06-DB/5), Schweizerischer Nationalfonds zur Förderung der wissenschaftlichen Forschung / Fonds national suisse de la recherche scientifique (PZ00P2_174028), United Kingdom Science Technology and Facilities Council (630008203), NASA (80NSSC22K0117), National Science Foundation (2108465 and Graduate Research Fellowship DGE 1746045), Princeton University through the Henry Norris Russell Fellowship, Universidad La Laguna through the Margarita Salas Fellowship from the Spanish Ministerio de Universidades and under the EU Next Generation funds (UNI/551/2021-May 26), and the Generalitat de Catalunya (CERCA programme).Peer reviewe

    The CARMENES search for exoplanets around M dwarfs

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    Context. The CARMENES instrument, installed at the 3.5 m telescope of the Calar Alto Observatory in AlmerĂ­a, Spain, was conceived to deliver high-accuracy radial velocity (RV) measurements with long-term stability to search for temperate rocky planets around a sample of nearby cool stars. Moreover, the broad wavelength coverage was designed to provide a range of stellar activity indicators to assess the nature of potential RV signals and to provide valuable spectral information to help characterise the stellar targets. Aims: We describe the CARMENES guaranteed time observations (GTO), spanning from 2016 to 2020, during which 19 633 spectra for a sample of 362 targets were collected. We present the CARMENES Data Release 1 (DR1), which makes public all observations obtained during the GTO of the CARMENES survey. Methods: The CARMENES survey target selection was aimed at minimising biases, and about 70% of all known M dwarfs within 10 pc and accessible from Calar Alto were included. The data were pipeline-processed, and high-level data products, including 18 642 precise RVs for 345 targets, were derived. Time series data of spectroscopic activity indicators were also obtained. Results: We discuss the characteristics of the CARMENES data, the statistical properties of the stellar sample, and the spectroscopic measurements. We show examples of the use of CARMENES data and provide a contextual view of the exoplanet population revealed by the survey, including 33 new planets, 17 re-analysed planets, and 26 confirmed planets from transiting candidate follow-up. A subsample of 238 targets was used to derive updated planet occurrence rates, yielding an overall average of 1.44 ± 0.20 planets with 1 M⊕ < Mpl sin i < 1000 M⊕ and 1 day < Porb < 1000 days per star, and indicating that nearly every M dwarf hosts at least one planet. All the DR1 raw data, pipeline-processed data, and high-level data products are publicly available online. Conclusions: CARMENES data have proven very useful for identifying and measuring planetary companions. They are also suitable for a variety of additional applications, such as the determination of stellar fundamental and atmospheric properties, the characterisation of stellar activity, and the study of exoplanet atmospheres

    Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis

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    BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London

    A tentative detection of He I in the atmosphere of GJ 1214 b

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    The He I λ10833 Å triplet is a powerful tool for characterising the upper atmosphere of exoplanets and tracing possible mass loss. Here, we analysed one transit of GJ 1214 b observed with the CARMENES high-resolution spectrograph to study its atmosphere via transmission spectroscopy around the He I triplet. Although previous studies using lower resolution instruments have reported non-detections of He I in the atmosphere of GJ 1214 b, we report here the first potential detection. We reconcile the conflicting results arguing that previous transit observations did not present good opportunities for the detection of He I, due to telluric H2O absorption and OH emission contamination. We simulated those earlier observations, and show evidence that the planetary signal was contaminated. From our single non-telluric-contaminated transit, we determined an excess absorption of 2.10−0.50+0.45% (4.6 σ) with a full width at half maximum (FWHM) of 1.30−0.25+0.30 Å. The detection of He I is statistically significant at the 4.6 σ level, but repeatability of the detection could not be confirmed due to the availability of only one transit. By applying a hydrodynamical model and assuming an H/He composition of 98/2, we found that GJ 1214 b would undergo hydrodynamic escape in the photon-limited regime, losing its primary atmosphere with a mass-loss rate of (1.5–18) × 1010 g s−1 and an outflow temperature in the range of 2900–4400 K. Further high-resolution follow-up observations of GJ 1214 b are needed to confirm and fully characterise the detection of an extended atmosphere surrounding GJ 1214 b. If confirmed, this would be strong evidence that this planet has a primordial atmosphere accreted from the original planetary nebula. Despite previous intensive observations from space- and ground-based observatories, our He I excess absorption is the first tentative detection of a chemical species in the atmosphere of this benchmark sub-Neptune planet. © ESO 2022.CARMENES is an instrument at the Centro AstronĂłmico Hispano-AlemĂĄn (CAHA) at Calar Alto (AlmerĂ­a, Spain), operated jointly by the Junta de AndalucĂ­a and the Instituto de AstrofĂ­sica de AndalucĂ­a (CSIC). CARMENES was funded by the Max-Planck-Gesellschaft (MPG), the Consejo Superior de Investigaciones CientĂ­ficas (CSIC), the Ministerio de EconomĂ­a y Competitividad (MINECO) and the European Regional Development Fund (ERDF) through projects FICTS-2011-02, ICTS-2017-07-CAHA-4, and CAHA16-CE-3978, and the members of the CARMENES Consortium (Max-Planck-Institut fĂŒr Astronomie, Instituto de AstrofĂ­sica de AndalucĂ­a, Landessternwarte Königstuhl, Institut de CiĂšncies de l’Espai, Institut fĂŒr Astrophysik Göttingen, Universidad Complutense de Madrid, ThĂŒringer Landessternwarte Tautenburg, Instituto de AstrofĂ­sica de Canarias, Hamburger Sternwarte, Centro de AstrobiologĂ­a and Centro AstronĂłmico Hispano-AlemĂĄn), with additional contributions by the MINECO, the Deutsche Forschungsgemeinschaft (DFG) through the Major Research Instrumentation Programme and Research Unit FOR2544 “Blue Planets around Red Stars”, the Klaus Tschira Stiftung, the states of Baden-WĂŒrttemberg and Niedersachsen, and by the Junta de AndalucĂ­a. This work was based on data from the CARMENES data archive at CAB (CSIC-INTA) and made use of resources from the AstroPiso collaboration. We acknowledge financial support from the Agencia Estatal de InvestigaciĂłn of the Ministerio de Ciencia e InnovaciĂłn and the ERDF “A way of making Europe” through projects PID2019-109522GB-C5[1:4], PID2019-110689RB-I00, PGC2018-098153-B-C31, and the Centre of Excellence “Severo Ochoa” and “MarĂ­a de Maeztu” awards to the Instituto de AstrofĂ­sica de Canarias (CEX2019-000920-S), Instituto de AstrofĂ­sica de AndalucĂ­a (SEV-2017-0709), and Centro de AstrobiologĂ­a (MDM-2017-0737), the European Research Council under the Horizon 2020 Framework Program via the ERC Advanced Grant Origins no. 832428 and via grant agreement no. 694513, the Excellence Cluster ORIGINS funded by the DFG under Germany’s Excellence Strategy EXC-2094 no. 390783311, and the Generalitat de Catalunya via the CERCA programme.Peer reviewe

    A Multi-Step Process of Viral Adaptation to a Mutagenic Nucleoside Analogue by Modulation of Transition Types Leads to Extinction-Escape

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    Resistance of viruses to mutagenic agents is an important problem for the development of lethal mutagenesis as an antiviral strategy. Previous studies with RNA viruses have documented that resistance to the mutagenic nucleoside analogue ribavirin (1-ÎČ-D-ribofuranosyl-1-H-1,2,4-triazole-3-carboxamide) is mediated by amino acid substitutions in the viral polymerase that either increase the general template copying fidelity of the enzyme or decrease the incorporation of ribavirin into RNA. Here we describe experiments that show that replication of the important picornavirus pathogen foot-and-mouth disease virus (FMDV) in the presence of increasing concentrations of ribavirin results in the sequential incorporation of three amino acid substitutions (M296I, P44S and P169S) in the viral polymerase (3D). The main biological effect of these substitutions is to attenuate the consequences of the mutagenic activity of ribavirin —by avoiding the biased repertoire of transition mutations produced by this purine analogue—and to maintain the replicative fitness of the virus which is able to escape extinction by ribavirin. This is achieved through alteration of the pairing behavior of ribavirin-triphosphate (RTP), as evidenced by in vitro polymerization assays with purified mutant 3Ds. Comparison of the three-dimensional structure of wild type and mutant polymerases suggests that the amino acid substitutions alter the position of the template RNA in the entry channel of the enzyme, thereby affecting nucleotide recognition. The results provide evidence of a new mechanism of resistance to a mutagenic nucleoside analogue which allows the virus to maintain a balance among mutation types introduced into progeny genomes during replication under strong mutagenic pressure

    The CARMENES search for exoplanets around M dwarfs High-resolution optical and near-infrared spectroscopy of 324 survey stars

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    The CARMENES radial velocity (RV) survey is observing 324 M dwarfs to search for any orbiting planets. In this paper, we present the survey sample by publishing one CARMENES spectrum for each M dwarf. These spectra cover the wavelength range 520–1710 nm at a resolution of at least R >80 000, and we measure its RV, Hα emission, and projected rotation velocity. We present an atlas of high-resolution M-dwarf spectra and compare the spectra to atmospheric models. To quantify the RV precision that can be achieved in low-mass stars over the CARMENES wavelength range, we analyze our empirical information on the RV precision from more than 6500 observations. We compare our high-resolution M-dwarf spectra to atmospheric models where we determine the spectroscopic RV information content, Q, and signal-to-noise ratio. We find that for all M-type dwarfs, the highest RV precision can be reached in the wavelength range 700–900 nm. Observations at longer wavelengths are equally precise only at the very latest spectral types (M8 and M9). We demonstrate that in this spectroscopic range, the large amount of absorption features compensates for the intrinsic faintness of an M7 star. To reach an RV precision of 1 m s−1 in very low mass M dwarfs at longer wavelengths likely requires the use of a 10 m class telescope. For spectral types M6 and earlier, the combination of a red visual and a near-infrared spectrograph is ideal to search for low-mass planets and to distinguish between planets and stellar variability. At a 4 m class telescope, an instrument like CARMENES has the potential to push the RV precision well below the typical jitter level of 3–4 m s−1

    The CARMENES search for exoplanets around M dwarfs. Two temperate Earth-mass planet candidates around Teegarden’s Star

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    Context.Teegarden’s Star is the brightest and one of the nearest ultra-cool dwarfs in the solar neighbourhood. For its late spectral type (M7.0 V),the star shows relatively little activity and is a prime target for near-infrared radial velocity surveys such as CARMENES.Aims.As part of the CARMENES search for exoplanets around M dwarfs, we obtained more than 200 radial-velocity measurements of Teegarden’sStar and analysed them for planetary signals.Methods.We find periodic variability in the radial velocities of Teegarden’s Star. We also studied photometric measurements to rule out stellarbrightness variations mimicking planetary signals.Results.We find evidence for two planet candidates, each with 1.1M⊕minimum mass, orbiting at periods of 4.91 and 11.4 d, respectively. Noevidence for planetary transits could be found in archival and follow-up photometry. Small photometric variability is suggestive of slow rotationand old age.Conclusions.The two planets are among the lowest-mass planets discovered so far, and they are the first Earth-mass planets around an ultra-cooldwarf for which the masses have been determined using radial velocities.We thank the referee Rodrigo DĂ­az for a careful review andhelpful comments. M.Z. acknowledges support from the Deutsche Forschungs-gemeinschaft under DFG RE 1664/12-1 and Research Unit FOR2544 “BluePlanets around Red Stars”, project no. RE 1664/14-1. CARMENES isan instrument for the Centro AstronĂłmico Hispano-AlemĂĄn de Calar Alto(CAHA, AlmerĂ­a, Spain). CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de InvestigacionesCientĂ­ficas (CSIC), the European Union through FEDER/ERF FICTS-2011-02 funds, and the members of the CARMENES Consortium (Max-Planck-Institut fĂŒr Astronomie, Instituto de AstrofĂ­sica de AndalucĂ­a, LandessternwarteKönigstuhl, Institut de CiĂšncies de l’Espai, Institut fĂŒr Astrophysik Göttingen,Universidad Complutense de Madrid, ThĂŒringer Landessternwarte Tautenburg,Instituto de AstrofĂ­sica de Canarias, Hamburger Sternwarte, Centro de Astro-biologĂ­a and Centro AstronĂłmico Hispano-AlemĂĄn), with additional contribu-tions by the Spanish Ministry of Economy, the German Science Foundationthrough the Major Research Instrumentation Programme and DFG ResearchUnit FOR2544 “Blue Planets around Red Stars”, the Klaus Tschira Stiftung, thestates of Baden-WĂŒrttemberg and Niedersachsen, and by the Junta de AndalucĂ­a.Based on data from the CARMENES data archive at CAB (INTA-CSIC). Thisarticle is based on observations made with the MuSCAT2 instrument, devel-oped by ABC, at Telescopio Carlos SĂĄnchez operated on the island of Tener-ife by the IAC in the Spanish Observatorio del Teide. Data were partly col-lected with the 150-cm and 90-cm telescopes at the Sierra Nevada Observa-tory (SNO) operated by the Instituto de AstrofĂ­sica de AndalucĂ­a (IAA-CSIC).Data were partly obtained with the MONET/South telescope of the MOnitoringNEtwork of Telescopes, funded by the Alfried Krupp von Bohlen und HalbachFoundation, Essen, and operated by the Georg-August-UniversitĂ€t Göttingen,the McDonald Observatory of the University of Texas at Austin, and the SouthAfrican Astronomical Observatory. We acknowledge financial support from theSpanish Agencia Estatal de InvestigaciĂłn of the Ministerio de Ciencia, Inno-vaciĂłn y Universidades and the European FEDER/ERF funds through projectsAYA2015-69350-C3-2-P, AYA2016-79425-C3-1/2/3-P, AYA2018-84089, BES-2017-080769, BES-2017-082610, ESP2015-65712-C5-5-R, ESP2016-80435-C2-1/2-R, ESP2017-87143-R, ESP2017-87676-2-2, ESP2017-87676-C5-1/2/5-R, FPU15/01476, RYC-2012-09913, the Centre of Excellence ”Severo Ochoa”and ”MarĂ­a de Maeztu” awards to the Instituto de AstrofĂ­sica de Canarias (SEV-2015-0548), Instituto de AstrofĂ­sica de AndalucĂ­a (SEV-2017-0709), and Cen-tro de AstrobiologĂ­a (MDM-2017-0737), the Generalitat de Catalunya throughCERCA programme”, the Deutsches Zentrum fĂŒr Luft- und Raumfahrt throughgrants 50OW0204 and 50OO1501, the European Research Council through grant694513, the Italian Ministero dell’instruzione, dell’universitĂ  de della ricerca andUniversitĂ  degli Studi di Roma Tor Vergata through FFABR 2017 and “Mis-sion: Sustainability 2016”, the UK Science and Technology Facilities Council through grant ST/P000592/1, the Israel Science Foundation through grant848/16, the Chilean CONICYT-FONDECYT through grant 3180405, the Mexi-can CONACYT through grant CVU 448248, the JSPS KAKENHI through grantsJP18H01265 and 18H05439, and the JST PRESTO through grant JPMJPR1775
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