Water vapor detection in the transmission spectra of HD 209458 b with the CARMENES NIR channel

Methods. The water vapor absorption lines from the atmosphere of the planet are Doppler-shifted due to the large change in its radial velocity during transit. This shift is of the order of tens of km s^(−1) , whilst the Earth’s telluric and the stellar lines can be considered quasi-static. We took advantage of this shift to remove the telluric and stellar lines using SYSREM, which performs a principal component analysis including proper error propagation. The residual spectra contain the signal from thousands of planetary molecular lines well below the noise level. We retrieve the information from those lines by cross-correlating the residual spectra with models of the atmospheric absorption of the planet. Results. We find a cross-correlation signal with a signal-to-noise ratio (S/N) of 6.4, revealing H_(2)O in HD 209458 b. We obtain a net blueshift of the signal of –5.2^(+2.6)_(−1.3) km s^(−1) that, despite the large error bars, is a firm indication of day- to night-side winds at the terminator of this hot Jupiter. Additionally, we performed a multi-band study for the detection of H_(2)O individually from the three near infrared bands covered by CARMENES. We detect H_(2)O from its 0.96–1.06 µm band with a S/N of 5.8, and also find hints of a detection from the 1.06–1.26 µm band, with a low S/N of 2.8. No clear planetary signal is found from the 1.26–1.62 µm band. Conclusions. Our significant H_(2)O signal at 0.96–1.06 µm in HD 209458 b represents the first detection of H_(2)O from this band individually, the bluest one to date. The unfavorable observational conditions might be the reason for the inconclusive detection from the stronger 1.15 and 1.4 µm bands. H_(2)O is detected from the 0.96–1.06 µm band in HD 209458 b, but hardly in HD 189733 b, which supports a stronger aerosol extinction in the latter, in line with previous studies. Future data gathered at more stable conditions and with larger S/N at both optical and near-infrared wavelengths could help to characterize the presence of aerosols in HD 209458 b and other planets

Simultaneous optical and X-ray observations of flares and rotational modulation on the RS CVn binary HR 1099 (V711 Tau) from the MUSICOS 1998 campaign

We present simultaneous and continuous observations of the Hα, Hβ, He I D_3, Na I D_1,D_2 doublet and the Ca II H&K lines for the RS CVn system HR 1099. The spectroscopic observations were obtained during the MUSICOS 1998 campaign involving several observatories and instruments, both echelle and long-slit spectrographs. During this campaign, HR 1099 was observed almost continuously for more than 8 orbits of 2^d.8. Two large optical flares were observed, both showing an increase in the emission of Hα, Ca II H K, Hβ and He I D_3 and a strong filling-in of the Na I D_1, D_2 doublet. Contemporary photometric observations were carried out with the robotic telescopes APT-80 of Catania and Phoenix-25 of Fairborn Observatories. Maps of the distribution of the spotted regions on the photosphere of the binary components were derived using the Maximum Entropy and Tikhonov photometric regularization criteria. Rotational modulation was observed in Hα and He I D_3 in anti-correlation with the photometric light curves. Both flares occurred at the same binary phase (0.85), suggesting that these events took place in the same active region. Simultaneous X-ray observations, performed by ASM on board RXTE, show several flare-like events, some of which correlate well with the observed optical flares. Rotational modulation in the X-ray light curve has been detected with minimum flux when the less active G5 V star was in front. A possible periodicity in the X-ray flare-like events was also found

Incidence of debris discs around FGK stars in the solar neighbourhood

Context. Debris discs are a consequence of the planet formation process and constitute the fingerprints of planetesimal systems. Their counterparts in the solar system are the asteroid and Edgeworth-Kuiper belts. Aims. The aim of this paper is to provide robust numbers for the incidence of debris discs around FGK stars in the solar neighbourhood. Methods. The full sample of 177 FGK stars with d ≤ 20 pc proposed for the DUst around NEarby Stars (DUNES) survey is presented. Herschel/PACS observations at 100 and 160 μm were obtained, and were complemented in some cases with data at 70 μm and at 250, 350, and 500 μm SPIRE photometry. The 123 objects observed by the DUNES collaboration were presented in a previous paper. The remaining 54 stars, shared with the Disc Emission via a Bias-free Reconnaissance in IR and Sub-mm (DEBRIS) consortium and observed by them, and the combined full sample are studied in this paper. The incidence of debris discs per spectral type is analysed and put into context together with other parameters of the sample, like metallicity, rotation and activity, and age. Results. The subsample of 105 stars with d ≤ 15 pc containing 23 F, 33 G, and 49 K stars is complete for F stars, almost complete for G stars, and contains a substantial number of K stars from which we draw solid conclusions on objects of this spectral type. The incidence rates of debris discs per spectral type are 0.26^+0.21_-0.14 (6 objects with excesses out of 23 F stars), 0.21^+0.17_-0.11 (7 out of 33 G stars), and 0.20^+0.14_-0.09 (10 out of 49 K stars); the fraction for all three spectral types together is 0.22^+0.08_-0.07 (23 out of 105 stars). The uncertainties correspond to a 95% confidence level. The medians of the upper limits of L_dust/L_∗ for each spectral type are 7.8 × 10^-7 (F), 1.4 × 10^-6 (G), and 2.2 × 10^-6 (K); the lowest values are around 4.0 × 10^-7. The incidence of debris discs is similar for active (young) and inactive (old) stars. The fractional luminosity tends to drop with increasing age, as expected from collisional erosion of the debris belts

Exoplanets around Low-mass Stars Unveiled by K2

We present the detection and follow-up observations of planetary candidates around low-mass stars observed by the K2 mission. Based on light-curve analysis, adaptive-optics imaging, and optical spectroscopy at low and high resolution (including radial velocity measurements), we validate 16 planets around 12 low-mass stars observed during K2 campaigns 5-10. Among the 16 planets, 12 are newly validated, with orbital periods ranging from 0.96 to 33 days. For one of the planets (K2-151b), we present ground-based transit photometry, allowing us to refine the ephemerides. Combining our K2 M-dwarf planets together with the validated or confirmed planets found previously, we investigate the dependence of planet radius R-p on stellar insolation and metallicity [Fe/H]. We confirm that for periods P less than or similar to 2 days, planets with a radius R-p greater than or similar to 2 R-circle plus are less common than planets with a radius between 1-2 R-circle plus. We also see a hint of the "radius valley" between 1.5 and 2 R-circle plus, which has been seen for close-in planets around FGK stars. These features in the radius/period distribution could be attributed to photoevaporation of planetary envelopes by high-energy photons from the host star, as they have for FGK stars. For the M dwarfs, though, the features are not as well defined, and we cannot rule out other explanations such as atmospheric loss from internal planetary heat sources or truncation of the protoplanetary disk. There also appears to be a relation between planet size and metallicity: the few planets larger than about 3 R-circle plus are found around the most metal-rich M dwarfs

CARMENES: an overview six months after first light

The CARMENES instrument is a pair of high-resolution (R greater than or similar to 80, 000) spectrographs covering the wavelength range from 0.52 to 1.71 mu m, optimized for precise radial velocity measurements. It was installed and commissioned at the 3.5 m telescope of the Calar Alto observatory in Southern Spain in 2015. The first large science program of CARMENES is a survey of similar to 300 M dwarfs, which started on Jan 1, 2016. We present an overview of all subsystems of CARMENES (front end, fiber system, visible-light spectrograph, near-infrared spectrograph, calibration units, etalons, facility control, interlock system, instrument control system, data reduction pipeline, data flow, and archive), and give an overview of the assembly, integration, verification, and commissioning phases of the project. We show initial results and discuss further plans for the scientific use of CARMENES

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

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

Stellar activity analysis of Barnard’s Star: very slow rotation and evidence for long-term activity cycle

The search for Earth-like planets around late-type stars using ultrastable spectrographs requires a very precise characterization of the stellar activity and the magnetic cycle of the star, since these phenomena induce radial velocity (RV) signals that can be misinterpreted as planetary signals. Among the nearby stars, we have selected Barnard’s Star (Gl 699) to carry out a characterization of these phenomena using a set of spectroscopic data that covers about 14.5 yr and comes from seven different spectrographs: HARPS, HARPS-N, CARMENES, HIRES, UVES, APF, and PFS; and a set of photometric data that covers about 15.1 yr and comes from four different photometric sources: ASAS, FCAPT–RCT, AAVSO, and SNO. We have measured different chromospheric activity indicators (H α, Ca II HK, and Na I D), as well as the full width at half-maximum (FWHM), of the cross-correlation function computed for a sub-set of the spectroscopic data. The analysis of generalized Lomb–Scargle periodograms of the time series of different activity indicators reveals that the rotation period of the star is 145 ± 15 d, consistent with the expected rotation period according to the low activity level of the star and previous claims. The upper limit of the predicted activity-induced RV signal corresponding to this rotation period is about 1 m s^(−1). We also find evidence of a long-term cycle of 10 ± 2 yr that is consistent with previous estimates of magnetic cycles from photometric time series in other M stars of similar activity levels. The available photometric data of the star also support the detection of both the long-term and the rotation signals

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