Examinando por Autor "Quirrenbach, A."

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Acceso Abierto
A He I upper atmosphere around the warm Neptune GJ 3470 b
(EDP Sciences, 2020-06-11) Pallé, E.; Nortmann, L.; Casasayas Barris, N.; Lampón, M.; López Puertas, M.; Caballero, J. A.; Sanz Forcada, J.; Lara, L. M.; Nagel, E.; Yan, F.; Alonso Floriano, F. J.; Amado, P. J.; Chen, G.; Cifuentes, C.; Cortés Contreras, M.; Czesla, S.; Molaverdikhani, K.; Montes, D.; Passegger, V. M.; Quirrenbach, A.; Reiners, A.; Ribas, I.; Sánchez López, A.; Schweitzer, A.; Strangret, M.; Zapatero Osorio, M. R.; Zechmeister, M.; Agencia Estatal de Investigación (AEI); Ministerio de Economía y Competitividad (MINECO); National Natural Science Foundation of China (NSFC); 0000-0003-0987-1593; 0000-0002-2891-8222; 0000-0003-2941-7734; 0000-0002-7349-1387; 0000-0003-3734-9866; 0000-0001-5664-2852; 0000-0002-6532-4378; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
High resolution transit spectroscopy has proven to be a reliable technique for the characterization of the chemical composition of exoplanet atmospheres. Taking advantage of the broad spectral coverage of the CARMENES spectrograph, we initiated a survey aimed at characterizing a broad range of planetary systems. Here, we report our observations of three transits of GJ 3470 b with CARMENES in search of He (2(3)S) absorption. On one of the nights, the He & x202f;Iregion was heavily contaminated by OH(-)telluric emission and, thus, it was not useful for our purposes. The remaining two nights had a very different signal-to-noise ratio (S/N) due to weather. They both indicate the presence of He (2(3)S) absorption in the transmission spectrum of GJ 3470 b, although a statistically valid detection can only be claimed for the night with higher S/N. For that night, we retrieved a 1.5 +/- 0.3% absorption depth, translating into aR(p)(lambda)/R-p= 1.15 +/- 0.14 at this wavelength. Spectro-photometric light curves for this same night also indicate the presence of extra absorption during the planetary transit with a consistent absorption depth. The He (2(3)S) absorption is modeled in detail using a radiative transfer code, and the results of our modeling efforts are compared to the observations. We find that the mass-loss rate,& x1e40;, is confined to a range of 3 x 10(10)g s(-1)forT= 6000 K to 10 x 10(10)g s(-1)forT= 9000 K. We discuss the physical mechanisms and implications of the He & x202f;Idetection in GJ 3470 b and put it in context as compared to similar detections and non-detections in other Neptune-size planets. We also present improved stellar and planetary parameter determinations based on our visible and near-infrared observations. © ESO 2020.
Acceso Abierto
CARMENES input catalog of M dwarfs VI. A time-resolved Ca II H&K catalog from archival data
(EDP Sciences, 2021-08-20) Perdelwitz, V.; Mittag, M.; Tal Or, L.; Schmitt, J. H. M. M.; Caballero, J. A.; Jeffers, S. V.; Reiners, A.; Schweitzer, A.; Trifonov, T.; Ribas, I.; Quirrenbach, A.; Amado, P. J.; Seifert, W.; Cifuentes, C.; Cortés Contreras, M.; Montes, D.; Revilla, D.; Skrzypinski, S. L.; Agencia Estatal de Investigación (AEI); Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC; Centro de Excelencia Científica Severo Ochoa Instituto de Astrofísica de Canarias; Perdelwitz, V. [0000-0002-6859-0882]; Tal Or, L. [0000-0003-3757-1440]; Caballero, J. A. [0000-0002-7349-1387]; Reiners, A. [0000-0003-1242-5922]; Schweitzer, A. [0000-0002-1624-0389]; Ribas, I. [0000-0002-6689-0312]; Amado, P. J. [0000-0001-8012-3788]; Cifuentes, C. [0000-0003-1715-5087]; Cortés Contreras, M. [0000-0003-3734-9866]; Skrzypinski, S. L. [0000-0002-0926-9888]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709
Context. Radial-velocity (RV) jitter caused by stellar magnetic activity is an important factor in state-of-the-art exoplanet discovery surveys such as CARMENES. Stellar rotation, along with heterogeneities in the photosphere and chromosphere caused by activity, can result in false-positive planet detections. Hence, it is necessary to determine the stellar rotation period and compare it to any putative planetary RV signature. Long-term measurements of activity indicators such as the chromospheric emission in the Ca II H&K lines (RHK′) enable the identification of magnetic activity cycles. Aims. In order to determine stellar rotation periods and study the long-term behavior of magnetic activity of the CARMENES guaranteed time observations (GTO) sample, it is advantageous to extract RHK′ time series from archival data, since the CARMENES spectrograph does not cover the blue range of the stellar spectrum containing the Ca II H&K lines. Methods. We have assembled a catalog of 11 634 archival spectra of 186 M dwarfs acquired by seven different instruments covering the Ca II H&K regime: ESPaDOnS, FEROS, HARPS, HIRES, NARVAL, TIGRE, and UVES. The relative chromospheric flux in these lines, RHK′, was directly extracted from the spectra by rectification with PHOENIX synthetic spectra via narrow passbands around the Ca II H&K line cores. Results. The combination of archival spectra from various instruments results in time series for 186 stars from the CARMENES GTO sample. As an example of the use of the catalog, we report the tentative discovery of three previously unknown activity cycles of M dwarfs. Conclusions. We conclude that the method of extracting with the use of model spectra yields consistent results for different instruments and that the compilation of this catalog will enable the analysis of long-term activity time series for a large number of M dwarfs.
Acceso Abierto
Discriminating between hazy and clear hot-Jupiter atmospheres with CARMENES.
(EDP Sciences, 2020-10-27) Sánchez López, A.; López Puertas, M.; Snellen, I. A. G.; Nagel, E.; Bauer, F. F.; Pallé, E.; Tal Or, L.; Amado, P. J.; Caballero, P. J.; Czesla, S.; Nortmann, L.; Reiners, A.; Ribas, I.; Quirrenbach, A.; Aceituno, J.; Béjar, V. J. S.; Casasayas Barris, N.; Henning, T.; Molaverdikhani, K.; Montes, D.; Stangret, M.; Zapatero Osorio, M. R.; Zechmeister, M.; European Research Council (ERC); Deutsche Forschungsgemeinschaft (DFG); Agencia Estatal de Investigación (AEI); Ministerio de Economía y Competitividad (MINECO); Ministerio de Ciencia e Innovación (MICINN); Pallé, E. [0000-0003-0987-1593]; Sánchez López, A. [0000-0002-0516-7956]; Nagel, E. [0000-0002-4019-3631]; Montes, D. [0000-0002-7779-238X]; Molaverdikhani, K. [0000-0002-0502-0428]; López Puertas, M. [0000-0003-2941-7734]; Snellen, I. A. G. [0000-0003-1624-3667]; Centro de Excelencia Científica Severo Ochoa Instituto de Astrofísica de Andalucía CSIC, SEV-2017-0709; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. Relatively large radii of some hot Jupiters observed in the ultraviolet and blue-optical are generally interpreted to be due to Rayleigh scattering by high-altitude haze particles. However, the haze composition and its production mechanisms are not fully understood, and observational information is still limited. Aims. We aim to study the presence of hazes in the atmospheres of HD 209458 b and HD 189733 b with high spectral resolution spectra by analysing the strength of water vapour cross-correlation signals across the red optical and near-infrared wavelength ranges. Methods. A total of seven transits of the two planets were observed with the CARMENES spectrograph at the 3.5 m Calar Alto telescope. Their Doppler-shifted signals were disentangled from the telluric and stellar contributions using the detrending algorithm SYSREM. The residual spectra were subsequently cross-correlated with water vapour templates at 0.70–0.96 μm to measure the strength of the water vapour absorption bands. Results. The optical water vapour bands were detected at 5.2σ in HD 209458 b in one transit, whereas no evidence of them was found in four transits of HD 189733 b. Therefore, the relative strength of the optical water bands compared to those in the near-infrared were found to be larger in HD 209458 b than in HD 189733 b. Conclusions. We interpret the non-detection of optical water bands in the transmission spectra of HD 189733 b, compared to the detection in HD 209458 b, to be due to the presence of high-altitude hazes in the former planet, which are largely absent in the latter. This is consistent with previous measurements with the Hubble Space Telescope. We show that currently available CARMENES observations of hot Jupiters can be used to investigate the presence of haze extinction in their atmospheres.
Acceso Abierto
Evidence of energy-, recombination-, and photon-limited escape regimes in giant planet H/He atmospheres
(EDP Sciences, 2021-04-23) Lampón, M.; López Puertas, M.; Czesla, S.; Sánchez López, A.; Lara, L. M.; Salz, M.; Sanz Forcada, J.; Molaverdikhani, K.; Quirrenbach, A.; Pallé, E.; Caballero, J. A.; Henning, T.; Nortmann, L.; Amado, P. J.; Montes, D.; Reiners, A.; Ribas, I.; Consejo Superior de Investigaciones Científicas (CSIC); Junta de Andalucía; European Regional Development Fund (ERDF); Deutsche Forschungsgemeinschaft (DFG); Agencia Estatal de Investigación (AEI); Ministerio de Economía y Competitividad (MINECO); Generalitat de Catalunya; European Research Council (ERC); Lampón, M. [0000-0002-0183-7158]; López Puertas, M. [0000-0003-2941-7734]; Sánchez López, A. [0000-0002-0516-7956]; Lara, L. M. [0000-0002-7184-920X]; Sanz Forcada, J. [0000-0002-1600-7835]; Molaverdikhani, K. [0000-0002-0502-0428]; Caballero, J. A. [0000-0002-7349-1387]; Nortmann, L. [0000-0001-8419-8760]; Amado, P. J. [0000-0001-8012-3788]; Montes, D. [0000-0002-7779-238X]; Ribas, I. [0000-0002-6689-0312]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737; Centro de Excelencia Científica Severo Ochoa Instituto de Astrofísica de Andalucía , SEV-2017-0709; Centro de Excelencia Científica Severo Ochoa Instituto de Astrofísica de Canarias, SEV-2015-0548
Hydrodynamic escape is the most efficient atmospheric mechanism of planetary mass loss and has a large impact on planetary evolution. Three hydrodynamic escape regimes have been identified theoretically: energy-limited, recombination-limited, and photon-limited. However, no evidence of these regimes had been reported until now. Here, we report evidence of these three regimes via an analysis of a helium I triplet at 10 830 Å and Lyα absorption involving a 1D hydrodynamic model that allows us to estimate hydrogen recombination and advection rates. In particular, we show that HD 209458 b is in the energy-limited regime, HD 189733 b is in the recombination-limited regime, and GJ 3470 b is in the photon-limited regime. These exoplanets can be considered as benchmark cases for their respective regimes.
Acceso Abierto
He I λ 10 830 Å in the transmission spectrum of HD209458 b
(EDP Sciences, 2019-09-12) Alonso Floriano, F. J.; Snellen, I. A. G.; Czesla, S.; Bauer, F. F.; Salz, M.; Lampón, M.; Lara, L. M.; Nagel, E.; López Puertas, M.; Nortmann, L.; Sánchez López, A.; Sanz Forcada, J.; Caballero, J. A.; Reiners, A.; Ribas, I.; Quirrenbach, A.; Amado, P. J.; Aceituno, J.; Anglada Escudé, G.; Béjar, V. J. S.; Brinkmöller, M.; Hatzes, A. P.; Henning, T.; Kaminski, A.; Kürster, M.; Labarga, F.; Montes, D.; Pallé, E.; Schmitt, J. H. M. M.; Zapatero Osorio, M. R.; Ministerio de Economía y Competitividad (MINECO); Max-Planck-Gesellschaft (MPG); European Research Council (ERC); Comunidad de Madrid; Agencia Estatal de Investigación (AEI); Alonso Floriano, F. J. [0000-0003-1202-5734]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709
Context. Recently, the He I triplet at 10 830 Å was rediscovered as an excellent probe of the extended and possibly evaporating atmospheres of close-in transiting planets. This has already resulted in detections of this triplet in the atmospheres of a handful of planets, both from space and from the ground. However, while a strong signal is expected for the hot Jupiter HD 209458 b, only upper limits have been obtained so far. Aims. Our goal is to measure the helium excess absorption from HD 209458 b and assess the extended atmosphere of the planet and possible evaporation. Methods. We obtained new high-resolution spectral transit time-series of HD 209458 b using CARMENES at the 3.5 m Calar Alto telescope, targeting the He I triplet at 10 830 Å at a spectral resolving power of 80 400. The observed spectra were corrected for stellar absorption lines using out-of-transit data, for telluric absorption using the MOLECFIT software, and for the sky emission lines using simultaneous sky measurements through a second fibre. Results. We detect He I absorption at a level of 0.91 ± 0.10% (9 σ) at mid-transit. The absorption follows the radial velocity change of the planet during transit, unambiguously identifying the planet as the source of the absorption. The core of the absorption exhibits a net blueshift of 1.8 ± 1.3 km s−1. Possible low-level excess absorption is seen further blueward from the main absorption near the centre of the transit, which could be caused by an extended tail. However, this needs to be confirmed. Conclusions. Our results further support a close relation between the strength of planetary absorption in the helium triplet lines and the level of ionising, stellar X-ray, and extreme-UV irradiation.
Acceso Abierto
Ionized calcium in the atmospheres of two ultra-hot exoplanets WASP-33b and KELT-9b
(EDP Sciences, 2019-12-05) Yan, F.; Casasayas Barris, N.; Molaverdikhani, K.; Alonso Floriano, F. J.; Reiners, A.; Pallé, E.; Henning, T.; Mollière, P.; Chen, G.; Nortmann, L.; Snellen, I. A. G.; Ribas, I.; Quirrenbach, A.; Caballero, J. A.; Amado, P. J.; Azzaro, M.; Bauer, F. F.; Cortés Contreras, M.; Czesla, S.; Khalafinejad, S.; Lara, L. M.; López Puertas, M.; Montes, D.; Nagel, E.; Oshagh, M.; Sánchez López, A.; Strangret, M.; Zechmeister, M.; European Research Council (ERC); Deutsche Forschungsgemeinschaft (DFG); Chen, G. [0000-0003-0740-5433]; Ribas, I. [0000-0002-6689-0312]; Montes, D. [0000-0002-7779-238X]; Yan, F. [0000-0001-9585-9034]; Molaverdikhani, K. [0000-0002-0502-0428]; Molliere, P. [0000-0003-4096-7067]; Lara, L. M. [0000-0002-7184-920X]; Nagel, E. [0000-0002-4019-3631]; Amado, P. J. [0000-0002-8388-6040]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Ultra-hot Jupiters are emerging as a new class of exoplanets. Studying their chemical compositions and temperature structures will improve our understanding of their mass loss rate as well as their formation and evolution. We present the detection of ionized calcium in the two hottest giant exoplanets - KELT-9b and WASP-33b. By using transit datasets from CARMENES and HARPS-N observations, we achieved high-confidence-level detections of Ca II using the cross-correlation method. We further obtain the transmission spectra around the individual lines of the Ca II H&K doublet and the near-infrared triplet, and measure their line profiles. The Ca II H&K lines have an average line depth of 2.02 +/- 0.17% (effective radius of 1.56 R-p) for WASP-33b and an average line depth of 0.78 +/- 0.04% (effective radius of 1.47 R-p) for KELT-9b, which indicates that the absorptions are from very high upper-atmosphere layers close to the planetary Roche lobes. The observed Ca II lines are significantly deeper than the predicted values from the hydrostatic models. Such a discrepancy is probably a result of hydrodynamic outflow that transports a significant amount of Ca II into the upper atmosphere. The prominent Ca II detection with the lack of significant Ca I detection implies that calcium is mostly ionized in the upper atmospheres of the two planets.
Acceso Abierto
Is there Na i in the atmosphere of HD 209458b?: Effect of the centre-to-limb variation and Rossiter-McLaughlin effect in transmission spectroscopy studies
(EDP Sciences, 2020-04-03) Casasayas Barris, N.; Pallé, E.; Yan, F.; Chen, G.; Luque, R.; Strangret, M.; Nagel, E.; Zechmeister, M.; Oshagh, M.; Sanz Forcada, J.; Nortmann, L.; Alonso Floriano, F. J.; Molaverdikhani, K.; Montes, D.; Quirrenbach, A.; Reiners, A.; Ribas, I.; Sánchez López, A.; Zapatero Osorio, M. R.; Deutsche Forschungsgemeinschaft (DFG); Agencia Estatal de Investigación (AEI); Junta de Andalucía; National Natural Science Foundation of China (NSFC); 0000-0002-2891-8222; 0000-0003-0987-1593; 0000-0001-6470-2907; 0000-0001-5664-2852; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
HD 209458b was the first transiting planet discovered, and the first for which an atmosphere, in particular Na I, was detected. With time, it has become one of the most frequently studied planets, with a large diversity of atmospheric studies using low- and high-resolution spectroscopy. Here, we present transit spectroscopy observations of HD 209458b using the HARPS-N and CARMENES spectrographs. We fit the Rossiter-McLaughlin effect by combining radial velocity data from both instruments (nine transits in total), measuring a projected spin-orbit angle of - 1.6 ± 0.3 deg. We also present the analysis of high-resolution transmission spectroscopy around the Na I region at 590 nm, using a total of five transit observations. In contrast to previous studies where atmospheric Na I absorption is detected, we find that for all of the nights, whether individually or combined, the transmission spectra can be explained by the combination of the centre-to-limb variation and the Rossiter-McLaughlin effect. This is also observed in the time-evolution maps and transmission light curves, but at lower signal-to-noise ratio. Other strong lines such as Hα, Ca II IRT, the Mg I triplet region, and K I D1 are analysed, and are also consistent with the modelled effects, without considering any contribution from the exoplanet atmosphere. Thus, the transmission spectrum reveals no detectable Na I absorption in HD 209458b. We discuss how previous pioneering studies of this benchmark object may have overlooked these effects. While for some star-planet systems these effects are small, for other planetary atmospheres the results reported in the literature may require revision. © ESO 2020.
Acceso Abierto
Modelling the He i triplet absorption at 10 830 A in the atmosphere of HD 209458 b
(EDP Sciences, 2020-04-07) Lampón, M.; López Puertas, M.; Lara, L. M.; Sánchez López, A.; Salz, M.; Czesla, S.; Sanz Forcada, J.; Molaverdikhani, K.; Alonso Floriano, F. J.; Nortmann, L.; Caballero, J. A.; Bauer, F. F.; Pallé, E.; Montes, D.; Quirrenbach, A.; Nagel, E.; Ribas, I.; Reiners, A.; Amado, P. J.; Deutsche Forschungsgemeinschaft (DFG); Agencia Estatal de Investigación (AEI); Ministerio de Economía y Competitividad (MINECO); Junta de Andalucía; 0000-0002-0183-7158; 0000-0003-2941-7734; 0000-0002-7184-920X; 0000-0002-0516-7956; 0000-0002-0502-0428; 0000-0002-7349-1387; 0000-0003-1212-5225; 0000-0003-0987-1593; 0000-0002-7779-238X; 0000-0002-4019-3631; 0000-0002-6689-0312; 0000-0002-8388-6040; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709
Context. HD 209458 b is an exoplanet with an upper atmosphere undergoing blow-off escape that has mainly been studied using measurements of the Lyα absorption. Recently, high-resolution measurements of absorption in the He I triplet line at 10 830 A of several exoplanets (including HD 209458 b) have been reported, creating a new opportunity to probe escaping atmospheres. Aims. We aim to better understand the atmospheric regions of HD 209458 b from where the escape originates. Methods. We developed a 1D hydrodynamic model with spherical symmetry for the HD 209458 b thermosphere coupled with a non-local thermodynamic model for the population of the He I triplet state. In addition, we performed high-resolution radiative transfer calculations of synthetic spectra for the helium triplet lines and compared them with the measured absorption spectrum in order to retrieve information about the atmospheric parameters. Results. We find that the measured spectrum constrains the [H]/[H+] transition altitude occurring in the range of 1.2 RP-1.9 RP. Hydrogen is almost fully ionised at altitudes above 2.9 RP. We also find that the X-ray and extreme ultraviolet absorption takes place at effective radii from 1.16 to 1.30 RP, and that the He I triplet peak density occurs at altitudes from 1.04 to 1.60 RP. Additionally, the averaged mean molecular weight is confined to the 0.61-0.73 g mole-1 interval, and the thermospheric H/He ratio should be larger than 90/10, and most likely approximately 98/2. We also provide a one-to-one relationship between mass-loss rate and temperature. Based on the energy-limited escape approach and assuming heating efficiencies of 0.1-0.2, we find a mass-loss rate in the range of (0.42-1.00) ×1011 g s-1 and a corresponding temperature range of 7125-8125 K. Conclusions. The analysis of the measured He I triplet absorption spectrum significantly constrains the thermospheric structure of HD 209458 b and advances our knowledge of its escaping atmosphere. © ESO 2020.
Acceso Abierto
Modelling the He I triplet absorption at 10 830 Å in the atmospheres of HD 189733 b and GJ 3470 b
(EDP Sciences, 2021-03-23) Lampón, M.; López Puertas, M.; Sanz Forcada, J.; Sánchez López, A.; Molaverdikhani, K.; Czesla, S.; Quirrenbach, A.; Pallé, E.; Caballero, J. A.; Henning, T.; Salz, M.; Nortmann, L.; Aceituno, J.; Amado, P. J.; Bauer, F. F.; Montes, D.; Nagel, E.; Reiners, A.; Ribas, I.; European Regional Development Fund (ERDF); Deutsche Forschungsgemeinschaft (DFG); Agencia Estatal de Investigación (AEI); Generalitat de Catalunya; European Research Council (ERC); 0000-0002-0183-7158; 0000-0003-2941-7734; 0000-0002-1600-7835; 0000-0002-0516-7956; 0000-0002-7349-1387; 0000-0001-8419-8760; 0000-0001-8012-3788; 0000-0002-4019-3631; 0000-0002-6689-0312; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFÍSICA DE CANARIAS (IAC), SEV-2015-0548; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709
Characterising the atmospheres of exoplanets is key to understanding their nature and provides hints about their formation and evolution. High resolution measurements of the helium triplet absorption of highly irradiated planets have been recently reported, which provide a new means of studying their atmospheric escape. In this work we study the escape of the upper atmospheres of HD 189733 b and GJ 3470 b by analysing high resolution He I triplet absorption measurements and using a 1D hydrodynamic spherically symmetric model coupled with a non-local thermodynamic model for the He I triplet state. We also use the H density derived from Lyα observations to further constrain their temperatures, mass-loss rates, and H/He ratios. We have significantly improved our knowledge of the upper atmospheres of these planets. While HD 189733 b has a rather compressed atmosphere and small gas radial velocities, GJ 3470 b, on the other hand with a gravitational potential ten times smaller, exhibits a very extended atmosphere and large radial outflow velocities. Hence, although GJ 3470 b is much less irradiated in the X-ray and extreme ultraviolet radiation, and its upper atmosphere is much cooler, it evaporates at a comparable rate. In particular, we find that the upper atmosphere of HD 189733 b is compact and hot, with a maximum temperature of 12 400−300+400 K, with a very low mean molecular mass (H/He = (99.2/0.8) ± 0.1), which is almost fully ionised above 1.1 RP, and with a mass-loss rate of (1.1 ± 0.1) × 1011 g s−1. In contrast, the upper atmosphere of GJ 3470 b is highly extended and relatively cold, with a maximum temperature of 5100 ± 900 K, also with a very low mean molecular mass (H/He = (98.5/1.5)−1.5+1.0), which is not strongly ionised, and with a mass-loss rate of (1.9 ± 1.1) × 1011 g s−1. Furthermore, our results suggest that upper atmospheres of giant planets undergoing hydrodynamic escape tend to have a very low mean molecular mass (H/He ≳ 97/3).
Acceso Abierto
Multiple water band detections in the CARMENES near-infrared transmission spectrum of HD 189733 b
(EDP Sciences, 2019-01-10) Alonso Floriano, F. J.; Sánchez López, A.; Snellen, I. A. G.; López Puertas, M.; Nagel, E.; Amado, P. J.; Bauer, F. F.; Caballero, J. A.; Czesla, S.; Nortmann, L.; Pallé, E.; Salz, M.; Reiners, A.; Ribas, I.; Quirrenbach, A.; Aceituno, J.; Anglada Escudé, G.; Béjar, V. J. S.; Guenther, E. W.; Henning, T.; Kaminski, A.; Kürster, M.; Lampón, M.; Lara, L. M.; Montes, D.; Morales, J. C.; Tal Or, L.; Schmitt, J. H. M. M.; Zapatero Osorio, M. R.; Zechmeister, M.; European Research Council (ERC); Ministerio de Economía y Competitividad (MINECO); Ministerio de Ciencia e Innovación (MICINN); Agencia Estatal de Investigación (AEI); Zapatero Osorio, M. R. [0000-0001-5664-2852]; Ribas, I. [0000-0002-6689-0312]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Aims. We explore the capabilities of CARMENES for characterising hot-Jupiter atmospheres by targeting multiple water bands, in particular, those at 1.15 and 1.4 μm. Hubble Space Telescope observations suggest that this wavelength region is relevant for distinguishing between hazy and/or cloudy and clear atmospheres. Methods. We observed one transit of the hot Jupiter HD 189733 b with CARMENES. Telluric and stellar absorption lines were removed using SYSREM, which performs a principal component analysis including proper error propagation. The residual spectra were analysed for water absorption with cross-correlation techniques using synthetic atmospheric absorption models. Results. We report a cross-correlation peak at a signal-to-noise ratio (S/N) of 6.6, revealing the presence of water in the transmission spectrum of HD 189733 b. The absorption signal appeared slightly blueshifted at –3.9 ± 1.3 km s−1. We measured the individual cross-correlation signals of the water bands at 1.15 and 1.4 μm, finding cross-correlation peaks at S/N of 4.9 and 4.4, respectively. The 1.4 μm feature is consistent with that observed with the Hubble Space Telescope. Conclusions. The water bands studied in this work have been mainly observed in a handful of planets from space. Being able also to detect them individually from the ground at higher spectral resolution can provide insightful information to constrain the properties of exoplanet atmospheres. Although the current multi-band detections can not yet constrain atmospheric haze models for HD 189733 b, future observations at higher S/N could provide an alternative way to achieve this aim.
Acceso Abierto
The CARMENES search for exoplanets around M dwarfs Convective shift and starspot constraints from chromatic radial velocities
(EDP Sciences, 2020-09-10) Baroch, D.; Morales, J. C.; Ribas, I.; Herrero, E.; Rosich, A.; Perger, M.; Anglada Escudé, G.; Reiners, A.; Caballero, J. A.; Quirrenbach, A.; Amado, P. J.; Jeffers, S. V.; Cifuentes, C.; Passegger, V. M.; Schweitzer, A.; Lafarga, M.; Bauer, F. F.; Béjar, V. J. S.; Colomé, J.; Cortés Contreras, M.; Dreizler, S.; Galadí Enríquez, D.; Hatzes, A. P.; Henning, T.; Kaminski, A.; Kürster, M.; Montes, D.; Rodríguez López, C.; Zechmeister, M.; Deutsche Forschungsgemeinschaft (DFG); Agencia Estatal de Investigación (AEI); National Aeronautics and Space Administration (NASA); Baroch, D. [0000-0001-7568-5161]; Ribas, I. [0000-0002-6689-0312]; Montes, D. [0000-0002-7779-238X]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFÍSICA DE CANARIAS (IAC), SEV-2015-0548; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709
Context. Variability caused by stellar activity represents a challenge to the discovery and characterization of terrestrial exoplanets and complicates the interpretation of atmospheric planetary signals. Aims. We aim to use a detailed modeling tool to reproduce the effect of active regions on radial velocity measurements, which aids the identification of the key parameters that have an impact on the induced variability. Methods. We analyzed the effect of stellar activity on radial velocities as a function of wavelength by simulating the impact of the properties of spots, shifts induced by convective motions, and rotation. We focused our modeling effort on the active star YZ CMi (GJ 285), which was photometrically and spectroscopically monitored with CARMENES and the Telescopi Joan Oró. Results. We demonstrate that radial velocity curves at different wavelengths yield determinations of key properties of active regions, including spot-filling factor, temperature contrast, and location, thus solving the degeneracy between them. Most notably, our model is also sensitive to convective motions. Results indicate a reduced convective shift for M dwarfs when compared to solar-type stars (in agreement with theoretical extrapolations) and points to a small global convective redshift instead of blueshift. Conclusions. Using a novel approach based on simultaneous chromatic radial velocities and light curves, we can set strong constraints on stellar activity, including an elusive parameter such as the net convective motion effect.
Acceso Abierto
The CARMENES search for exoplanets around M dwarfs No evidence for a super-Earth in a 2-day orbit around GJ 1151
(EDP Sciences, 2021-05-07) Perger, M.; Ribas, I.; Anglada Escudé, G.; Morales, J. C.; Amado, P. J.; Caballero, J. A.; Quirrenbach, A.; Reiners, A.; Béjar, V. J. S.; Dreizler, S.; Galadí Enríquez, D.; Hatzes, A. P.; Henning, T.; Jeffers, S. V.; Kaminski, A.; Kürster, M.; Lafarga, M.; Montes, D.; Pallé, E.; Rodríguez López, C.; Schweitzer, A.; Zapatero Osorio, M. R.; Zechmeister, M.; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MINECO/ICTI2013-2016/MDM-2017-0737; Perger, M. [0000-0001-7098-0372]; Montes, D. [0000-0002-7779-238X]; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFÍSICA DE CANARIAS (IAC), SEV-2015-0548; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. The interaction between Earth-like exoplanets and the magnetic field of low-mass host stars are considered to produce weak emission signals at radio frequencies. A study using LOFAR data announced the detection of radio emission from the mid M-type dwarf GJ 1151 that could potentially arise from a close-in terrestrial planet. Recently, the presence of a 2.5-M⊕ planet orbiting GJ 1151 with a 2-day period has been claimed using 69 radial velocities (RVs) from the HARPS-N and HPF instruments. Aims. We have obtained 70 new high-precision RV measurements in the framework of the CARMENES M-dwarf survey and use these data to confirm the presence of the claimed planet and to place limits on possible planetary companions in the GJ 1151 system. Methods. We analysed the periodicities present in the combined RV data sets from all three instruments and calculated the detection limits for potential planets in short-period orbits. Results. We cannot confirm the recently announced candidate planet and conclude that the 2-day signal in the HARPS-N and HPF data sets is most probably produced by a long-term RV variability, possibly arising from an outer planetary companion that has yet to be constrained. We calculate a 99.9% significance detection limit of 1.50 m s−1 in the RV semi-amplitude, which places upper limits of 0.7 M⊕ and 1.2 M⊕ on the minimum masses of potential exoplanets with orbital periods of 1 and 5 days, respectively.
Acceso Abierto
The CARMENES search for exoplanets around M dwarfs Period search in Hα, Na I D, and Ca II IRT lines
(EDP Sciences, 2019-02-27) Fuhrmeister, B.; Czesla, S.; Schmitt, J. H. M. M.; Johnson, E. N.; Schöfer, P.; Jeffers, S. V.; Caballero, J. A.; Zechmeister, M.; Reiners, A.; Ribas, I.; Amado, P. J.; Quirrenbach, A.; Bauer, F. F.; Béjar, V. J. S.; Cortés Contreras, M.; Díez Alonso, E.; Dreizler, S.; Galadí Enríquez, D.; Guenther, E. W.; Kaminski, A.; Kürster, M.; Lafarga, M.; Montes, D.; Deutsche Forschungsgemeinschaft (DFG); Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
We use spectra from CARMENES, the Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Echelle Spectrographs, to search for periods in chromospheric indices in 16 M0–M2 dwarfs. We measure spectral indices in the Hα, the Ca II infrared triplet (IRT), and the Na I D lines to study which of these indices are best-suited to finding rotation periods in these stars. Moreover, we test a number of different period-search algorithms, namely the string length method, the phase dispersion minimisation, the generalized Lomb–Scargle periodogram, and the Gaussian process regression with quasi-periodic kernel. We find periods in four stars using Hα and in five stars using the Ca II IRT, two of which have not been found before. Our results show that both Hα and the Ca II IRT lines are well suited for period searches, with the Ca II IRT index performing slightly better than Hα. Unfortunately, the Na I D lines are strongly affected by telluric airglow, and we could not find any rotation period using this index. Further, different definitions of the line indices have no major impact on the results. Comparing the different search methods, the string length method and the phase dispersion minimisation perform worst, while Gaussian process models produce the smallest numbers of false positives and non-detections.
Acceso Abierto
The CARMENES search for exoplanets around M dwarfs Three temperate-to-warm super-Earths
(EDP Sciences, 2020-11-10) Stock, S.; Nagel, E.; Kemmer, J.; Passegger, V. M.; Reffert, S.; Quirrenbach, A.; Caballero, J. A.; Czesla, S.; Béjar, V. J. S.; Cardona Guillén, C.; Díez Alonso, E.; Herrero, E.; Lalitha, S.; Schlecker, M.; Tal Or, L.; Rodríguez, E.; Rodríguez López, C.; Ribas, I.; Reiners, A.; Amado, P. J.; Bauer, F. F.; Bluhm, P.; Cortés Contreras, M.; González Cuesta, L.; Dreizler, S.; Hatzes, A. P.; Henning, T.; Jeffers, S. V.; Kaminski, A.; Kürster, M.; Lafarga, M.; López González, M. J.; Montes, D.; Morales, J. C.; Pedraz, S.; Schöfer, P.; Schweitzer, A.; Trifonov, T.; Zapatero Osorio, M. R.; Zechmeister, M.; Agencia Estatal de Investigación (AEI); Generalitat de Catalunya; National Aeronautics and Space Administration (NASA); Tel-Aviv University (Israel); Stock, S. [0000-0002-1166-9338]; Nagel, E. [0000-0002-4019-3631]; Kemmer, J. [0000-0003-3929-1442]; Reffert, S. [0000-0002-0460-8289]; Caballero, J. A. [0000-0002-7349-1387]; Cardona, C. [0000-0002-2198-4200]; Schlecker, M. [0000-0001-8355-2107]; Tal Or, L. [0000-0003-3757-1440]; Rodríguez, E. [0000-0001-6827-9077]; Ribas, I. [0000-0002-6689-0312]; Amado, P. J. [0000-0002-8388-6040]; Cortés Contreras, M. [0000-0003-3734-9866]; González Cuesta, L. [0000-0002-1241-5508]; López González, M. J. [0000-0001-8104-5128]; Zapatero Osorio, M. R. [0000-0001-5664-2852]; Zechmeister, M. [0000-0002-6532-4378]; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFÍSICA DE CANARIAS (IAC), SEV-2015-0548
We announce the discovery of two planets orbiting the M dwarfs GJ 251 (0.360 ± 0.015M⊙) and HD 238090 (0.578 ± 0.021M⊙) based on CARMENES radial velocity (RV) data. In addition, we independently confirm with CARMENES data the existence of Lalande 21185 b, a planet that has recently been discovered with the SOPHIE spectrograph. All three planets belong to the class of warm or temperate super-Earths and share similar properties. The orbital periods are 14.24 d, 13.67 d, and 12.95 d and the minimum masses are 4.0 ± 0.4 M⊕, 6.9 ± 0.9 M⊕, and 2.7 ± 0.3 M⊕ for GJ 251 b, HD 238090 b, and Lalande 21185 b, respectively. Based on the orbital and stellar properties, we estimate equilibrium temperatures of 351.0 ± 1.4 K for GJ 251 b, 469.6 ± 2.6 K for HD 238090 b, and 370.1 ± 6.8 K for Lalande 21185 b. For the latter we resolve the daily aliases that were present in the SOPHIE data and that hindered an unambiguous determination of the orbital period. We find no significant signals in any of our spectral activity indicators at the planetary periods. The RV observations were accompanied by contemporaneous photometric observations. We derive stellar rotation periods of 122.1 ± 2.2 d and 96.7 ± 3.7 d for GJ 251 and HD 238090, respectively. The RV data of all three stars exhibit significant signals at the rotational period or its first harmonic. For GJ 251 and Lalande 21185, we also find long-period signals around 600 d, and 2900 d, respectively, which we tentatively attribute to long-term magnetic cycles. We apply a Bayesian approach to carefully model the Keplerian signals simultaneously with the stellar activity using Gaussian process regression models and extensively search for additional significant planetary signals hidden behind the stellar activity. Current planet formation theories suggest that the three systems represent a common architecture, consistent with formation following the core accretion paradigm.
Acceso Abierto
The CARMENES search for exoplanets around M dwarfs. The He I infrared triplet lines in PHOENIX models of M 2-3 V stars
(EDP Sciences, 2020-06-24) Hintz, D.; Fuhrmeister, B.; Czesla, S.; Schmitt, H. M. M.; Schweitzer, A.; Nagel, E.; Johnson, E. N.; Caballero, J. A.; Zechmeister, M.; Jeffers, S. V.; Reiners, A.; Ribas, I.; Amado, P. J.; Quirrenbach, A.; Anglada Escudé, G.; Bauer, F. F.; Béjar, V. J. S.; Cortés Contreras, M.; Dreizler, S.; Galadí Enríquez, D.; Guenther, E. W.; Hauschildt, P. H.; Kaminski, A.; Kürster, M.; Lafarga, M.; López del Fresno, M.; Montes, D.; Morales, J. C.; Deutsches Zentrum für Luft- und Raumfahrt (DLR); Deutsche Forschungsgemeinschaft (DFG); Agencia Estatal de Investigación (AEI); Ministerio de Economía y Competitividad (MINECO); 0000-0002-5274-2589; 0000-0001-6470-2907; 0000-0002-6532-4378; 0000-0003-1212-5225; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
The He » I infrared (IR) line at a vacuum wavelength of 10 833 Å is a diagnostic for the investigation of atmospheres of stars and planets orbiting them. For the first time, we study the behavior of the He » I IR line in a set of chromospheric models for M-dwarf stars, whose much denser chromospheres may favor collisions for the level population over photoionization and recombination, which are believed to be dominant in solar-type stars. For this purpose, we use published PHOENIX models for stars of spectral types M2 V and M3 V and also compute new series of models with different levels of activity following an ansatz developed for the case of the Sun. We perform a detailed analysis of the behavior of the He I IR line within these models. We evaluate the line in relation to other chromospheric lines and also the influence of the extreme ultraviolet (EUV) radiation field. The analysis of the He » I IR line strengths as a function of the respective EUV radiation field strengths suggests that the mechanism of photoionization and recombination is necessary to form the line for inactive models, while collisions start to play a role in our most active models. Moreover, the published model set, which is optimized in the ranges of the Na » I D2, Hα, and the bluest Ca » II IR triplet line, gives an adequate prediction of the He » I IR line for most stars of the stellar sample. Because especially the most inactive stars with weak He » I IR lines are fit worst by our models, it seems that our assumption of a 100% filling factor of a single inactive component no longer holds for these stars. © ESO 2020.
Acceso Abierto
The CARMENES search for exoplanets around M dwarfs: A super-Earth planet orbiting HD 79211 (GJ 338 B)
(EDP Sciences, 2020-05-27) González Álvarez, E.; Zapatero Osorio, M. R.; Caballero, J. A.; Sanz Forcada, J.; Béjar, V. J. S.; González Cuesta, L.; Dreizler, S.; Bauer, F. F.; Rodríguez, E.; Tal Or, L.; Zechmeister, M.; Montes, D.; López González, M. J.; Ribas, I.; Reiners, A.; Quirrenbach, A.; Amado, P. J.; Anglada Escudé, G.; Azzaro, M.; Cortés Contreras, M.; Hatzes, A. P.; Henning, T.; Jeffers, S. V.; Kaminski, A.; Kürster, M.; Lafarga, M.; Morales, J. C.; Pallé, E.; Perger, M.; Schmitt, H. M. M.; Agencia Estatal de Investigación (AEI); González Álvarez, E. https://orcid.org/0000-0002-4820-2053; Zapatero Osorio, M. R.https://orcid.org/0000-0001-5664-2852; Caballero, J. A. https://orcid.org/0000-0002-7349-1387; López González, M. J. https://orcid.org/0000-0002-0011-3086; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709
Aims. We report on radial velocity time series for two M0.0 V stars, GJ 338 B and GJ 338 A, using the CARMENES spectrograph, complemented by ground-telescope photometry from Las Cumbres and Sierra Nevada observatories. We aim to explore the presence of small planets in tight orbits using the spectroscopic radial velocity technique. Methods. We obtained 159 and 70 radial velocity measurements of GJ 338 B and A, respectively, with the CARMENES visible channel between 2016 January and 2018 October. We also compiled additional relative radial velocity measurements from the literature and a collection of astrometric data that cover 200 a of observations to solve for the binary orbit. Results. We found dynamical masses of 0.64 ± 0.07 M° for GJ 338 B and 0.69 ± 0.07 M° for GJ 338 A. The CARMENES radial velocity periodograms show significant peaks at 16.61 ± 0.04 d (GJ 338 B) and 16.3-1.3+3.5 d (GJ 338 A), which have counterparts at the same frequencies in CARMENES activity indicators and photometric light curves. We attribute these to stellar rotation. GJ 338 B shows two additional, significant signals at 8.27 ± 0.01 and 24.45 ± 0.02 d, with no obvious counterparts in the stellar activity indices. The former is likely the first harmonic of the star's rotation, while we ascribe the latter to the existence of a super-Earth planet with a minimum mass of 10.27-1.38+1.47 M⊕ orbiting GJ 338 B. We have not detected signals of likely planetary origin around GJ 338 A. Conclusions. GJ 338 Bb lies inside the inner boundary of the habitable zone around its parent star. It is one of the least massive planets ever found around any member of stellar binaries. The masses, spectral types, brightnesses, and even the rotational periods are very similar for both stars, which are likely coeval and formed from the same molecular cloud, yet they differ in the architecture of their planetary systems. © ESO 2020.
Acceso Abierto
The CARMENES search for exoplanets around M dwarfs: Characterization of the nearby ultra-compact multiplanetary system YZ Ceti
(EDP Sciences, 2020-05-01) Stock, S.; Kemmer, J.; Reffert, S.; Trifonov, T.; Kaminski, A.; Dreizler, S.; Quirrenbach, A.; Caballero, J. A.; Reiners, A.; Anglada Escudé, G.; Ribas, I.; Amado, P. J.; Barrado, D.; Barnes, J. R.; Bauer, F. F.; Berdiñas, Z. M.; Béjar, V. J. S.; Coleman, G. A. L.; Cortés Contreras, M.; Díez Alonso, E.; Domínguez Fernández, A. J.; Espinoza, N.; Haswell, C. A.; Hatzes, A.; Henning, T.; Jenkins, J. S.; Jones, H. R. A.; Kossakowski, D.; Kürster, M.; Lafarga, M.; Lee, M. H.; López González, M. J.; Montes, D.; Morales, J. C.; Morales, N.; Pallé, E.; Pedraz, S.; Rodríguez, E.; Rodríguez López, C.; Zechmeister, M.; Jeffers, S. V.; Deutsche Forschungsgemeinschaft (DFG); Agencia Estatal de Investigación (AEI); Comisión Nacional de Investigación Científica y Tecnológica (CONICYT); Ministerio de Economía y Competitividad (MINECO); Junta de Andalucía; European Research Council (ERC); Fondo Nacional de Desarrollo Científico y Tecnológico (FONDECYT); Science and Technology Facilities Council (STFC); Generalitat de Catalunya; 0000-0002-1166-9338; 0000-0003-3929-1442; 0000-0002-0460-8289; 0000-0002-0236-775X; 0000-0003-0203-8208; 0000-0002-7349-1387; 0000-0003-2490-4779; 0000-0002-6689-0312; 0000-0002-8388-6040; 0000-0003-1930-5683; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFISICA DE ANDALUCIA (IAA), SEV-2017-0709; Centros de Excelencia Severo Ochoa, INSTITUTO DE ASTROFÍSICA DE CANARIAS (IAC), SEV-2015-0548; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Acceso Abierto
The CARMENES search for exoplanets around M dwarfs: Radial velocities and activity indicators from cross-correlation functions with weighted binary masks
(EDP Sciences, 2020-04-13) Lafarga, M.; Ribas, I.; Lovis, C.; Perger, M.; Zechmeister, M.; Bauer, F.; Kürster, M.; Cortés Contreras, M.; Morales, J. C.; Herrero, E.; Rosich, A.; Baroch, D.; Reiners, A.; Caballero, J. A.; Quirrenbach, A.; Amado, P. J.; Alacid, J. M.; Béjar, V. J. S.; Dreizler, S.; Hatzes, A. P.; Henning, T.; Jeffers, S. V.; Kaminski, A.; Montes, D.; Pedraz, S.; Rodríguez López, C.; Schmitt, H. M. M.; 0000-0002-8815-9416; 0000-0002-6532-4378; 0000-0002-7349-1387; 0000-0001-9224-0455; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
Context. For years, the standard procedure to measure radial velocities (RVs) of spectral observations consisted in cross-correlating the spectra with a binary mask, that is, a simple stellar template that contains information on the position and strength of stellar absorption lines. The cross-correlation function (CCF) profiles also provide several indicators of stellar activity. Aims. We present a methodology to first build weighted binary masks and, second, to compute the CCF of spectral observations with these masks from which we derive radial velocities and activity indicators. These methods are implemented in a python code that is publicly available. Methods. To build the masks, we selected a large number of sharp absorption lines based on the profile of the minima present in high signal-to-noise ratio (S/N) spectrum templates built from observations of reference stars. We computed the CCFs of observed spectra and derived RVs and the following three standard activity indicators: full-width-at-half-maximum as well as contrast and bisector inverse slope. Results. We applied our methodology to CARMENES high-resolution spectra and obtain RV and activity indicator time series of more than 300 M dwarf stars observed for the main CARMENES survey. Compared with the standard CARMENES template matching pipeline, in general we obtain more precise RVs in the cases where the template used in the standard pipeline did not have enough S/N. We also show the behaviour of the three activity indicators for the active star YZ CMi and estimate the absolute RV of the M dwarfs analysed using the CCF RVs. © ESO 2020.