Precise mass and radius of a transiting super-Earth planet orbiting the M dwarf TOI-1235: a planet in the radius gap?

We report the confirmation of a transiting planet around the bright weakly active M0.5 V star TOI-1235 (TYC 4384–1735–1, V ≈ 11.5 mag), whose transit signal was detected in the photometric time series of sectors 14, 20, and 21 of the TESS space mission. We confirm the planetary nature of the transit signal, which has a period of 3.44 d, by using precise RV measurements with the CARMENES, HARPS-N, and iSHELL spectrographs, supplemented by high-resolution imaging and ground-based photometry. A comparison of the properties derived for TOI-1235 b with theoretical models reveals that the planet has a rocky composition, with a bulk density slightly higher than that of Earth. In particular, we measure a mass of M_(p) = 5.9 ± 0.6 M_(⊕) and a radius of Rp = 1.69 ± 0.08 R_(⊕), which together result in a density of ρ_(p) = 6.7^(+1.3)_(−1.1) g cm^(−3) . When compared with other well-characterized exoplanetary systems, the particular combination of planetary radius and mass places our discovery in the radius gap, which is a transition region between rocky planets and planets with significant atmospheric envelopes. A few examples of planets occupying the radius gap are known to date. While the exact location of the radius gap for M dwarfs is still a matter of debate, our results constrain it to be located at around 1.7 R_(⊕) or larger at the insolation levels received by TOI-1235 b (∼60 S_(⊕)). This makes it an extremely interesting object for further studies of planet formation and atmospheric evolution

A He I upper atmosphere around the warm Neptune GJ 3470 b

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 (23S) absorption. On one of the nights, the He I region 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 a R_(p)(λ)/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, Ṁ , is confined to a range of 3 × 10^(10) g s^(−1) for T = 6000 K to 10 × 10^(10) g s^(−1) for T = 9000 K. We discuss the physical mechanisms and implications of the He I detection 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

The CARMENES search for exoplanets around M dwarfs: The HeI infrared triplet lines in PHOENIX models of M 2-3 V stars

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 D_(2), 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

CARMENES-UCM: scientific preparation, multiplicity, chromospheric activity and kinematics

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Física de la Tierra, Astronomía y Astrofísica II (Astrofísica y Ciencias de la Atmósfera), leída el 07/11/2016. Tesis formato europeo (compendio de artículos)Las estrellas enanas de tipo M representan cerca de dos tercios de las estrellas en la Galaxia, lo que las convierte en objetivos perfectos para el estudio de formación y evolución estelar al final del diagrama Hertzsprung-Russell. El máximo de emisión de energía de las estrellas M se sitúa en el infrarrojo, entre 0.9 y 1.5 μm. Las Ms de campo tienen masas entre 0.6 y 0.08M8, lo que las sitúa entre las estrellas que queman helio e hidrógeno y los objetos subestelares. Por esta razón, no está delimitado el proceso de formación dominante, también relacionado con la frecuencia de enanas M y estrellas poco masivas en sistemas binarios y múltiples. Por otro lado, en el régimen de enanas M, tienen lugar importantes cambios en la estructura interna, pasando de ser parcial a totalmente convectivas hacia los últimos tipos en la secuencia principal. La poca masa de las enanas M las convierten en objetivos óptimos para la caza de exoplanetas, especialmente con el método Doppler, que saca provecho del elevado cociente entre la masa del planeta y la masa de la estrella. CARMENES es un espectrógrafo de alta resolución (R>80 000) con dos canales, visible (0.52–0.96 μm) e infrarrojo (0.96–1.71 μm), situados en el telescopio de 3.5m en el Observatorio de Calar Alto en Almería (España), cuyo propósito principal es la detección de exo-Tierras en la zona de habitabilidad de las enanas M. Esta tesis se ha desarrollado en el marco del proyecto CARMENES, bajo el auspicio del Consorcio homónimo, que está compuesto por 11 instituciones españolas y alemanas. El instrumento CARMENES, operativo desde enero de 2016, está observando entorno a 300 enanas M durante al menos 600 noches de tiempo garanizado. Estas observaciones durarán, al menos, tres años. El análisis llevado a cabo en esta tesis forma parte de la preparación científica necesaria para la selección de esas estrellas...M dwarfs represent near two-thirds of the stars in the Galaxy, which converts them into perfect targets for the study of stellar formation and evolution at the end of the Hertzsprung-Russell diagram. Their emission peaks in the infrared, between 0.9 and 1.5 μm. The low masses of field M dwarfs (from 0.6 to 0.08M8), place them between helium and hydrogen burning stars, and substellar objects. For this reason, there is no restricted their dominant formation process, also related to the frequency of M dwarfs and low mass stars in binary and multiple systems. On the other hand, in this regime, important structural changes take place, and they become fully convective towards later spectral subtypes in the main sequence. They are excellent targets for exoplanet hunting due to their low masses, especially with the Doppler method, which takes advantage of the high mass ratio between the star and the planet. CARMENES is a high-resolution spectrograph (R>80 000) with two chanels, visible (0.52–0.96 μm) and infrared (0.96–1.71 μm), located at the 3.5 telescope at the Calar Alto Observatory in Almería (Spain). Its main purpose is to detect exoEarths in the habitability zone of M dwarfs. This thesis has been developed in the frame of the CARMENES project, under the auspices of the CARMENES Consortium, which is composed by 11 German and Spanish institutions. The CARMENES instrument, operative since January 2016, is observing around 300 M dwarfs during at least 600 nights of guaranteed time during at least three years. The analysis carried out in this thesis is part of the science preparation needed for the target selection...Depto. de Física de la Tierra y AstrofísicaFac. de Ciencias FísicasTRUEunpu

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

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, Ha 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 4m 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 HD147379 b: A nearby Neptune in the temperate zone of an early-M dwarf

We report on the first star discovered to host a planet detected by radial velocity (RV) observations obtained within the CARMENES survey for exoplanets around M dwarfs. HD 147379 (V = 8.9 mag, M = 0.58 +/- 0.08 M-circle dot), a bright M0.0 V star at a distance of 10.7 pc, is found to undergo periodic RV variations with a semi-amplitude of K = 5.1 +/- 0.4 m s(-1) and a period of P = 86.54 +/- 0.06 d. The RV signal is found in our CARMENES data, which were taken between 2016 and 2017, and is supported by HIRES/Keck observations that were obtained since 2000. The RV variations are interpreted as resulting from a planet of minimum mass m(P) sin i = 25 +/- 2 M-circle plus, 1.5 times the mass of Neptune, with an orbital semi-major axis a = 0.32 au and low eccentricity (e < 0.13). HD 147379 b is orbiting inside the temperate zone around the star, where water could exist in liquid form. The RV time-series and various spectroscopic indicators show additional hints of variations at an approximate period of 21.1 d (and its first harmonic), which we attribute to the rotation period of the star

Reaching the boundary between stellar kinematic groups and very wide binaries. IV. The widest Washington double star systems with rho > 1000 arcsec in Gaia DR3

Aims: With the latest Gaia DR3 data, we analyse the widest pairs in the Washington Double Star (WDS) catalogue with angular separations, $\rho$, greater than 1000 arcsec. Methods: We confirmed the pair's membership to stellar systems based on common proper motions, parallaxes, and (when available) radial velocities, together with the locii of the individual components in colour-magnitude diagrams. We also looked for additional closer companions to the ultrawide pairs, either reported by WDS or found by us with a new Gaia astrometric search. In addition, we determined masses for each star (and white dwarf) and, with the projected physical separation, computed the gravitational potential energy, |Ug*|, of the systems. Results: Of the 155159 pairs currently catalogued by WDS, there are 504 with $\rho$ > 1000 arcsec. Of these, only 2 ultrawide pairs have not been identified, 10 do not have any available astrometry, 339 have not passed a conservative filtering in proper motion or parallax, 59 are members of young stellar kinematic groups, associations or open clusters, and only 94 remain as bona fide ultrawide pairs in the galactic field. Accounting for the additional members at shorter separations identified in a complementary astrometric and bibliographic search, we found 79 new stars (39 reported, plus 40 not reported by WDS) in 94 ultrawide stellar systems. This sample is expanded when including new close binary candidates with large Gaia DR3 RUWE, $\sigma_{Vr}$, or a proper motion anomaly. Furthermore, the large fraction of subsystems and the non-hierarchical configurations of many wide systems with three or more stars is remarkable.Comment: Accepted to A&A. 38 Pages, 8 figures and 9 tables (4 tables online

Ionized calcium in the atmospheres of two ultra-hot exoplanets WASP-33b and KELT-9b

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