Here, we present the results related to a new unique terrestrial ecosystem found in an englacial hypersaline brine found in Northern Victoria Land (Antarctica). Both the geochemistry and microbial ...(prokaryotic and fungal) diversity revealed an unicity with respect to all the other known Antarctic brines and suggested a probable ancient origin mainly due a progressive cryoconcentration of seawater. The prokaryotic community presented some peculiarities, such as the occurrence of sequences of Patescibacteria (which can thrive in nutrient-limited water environments) or few Spirochaeta, and the presence of archaeal sequences of Methanomicrobia closely related to Methanoculleus, a methanogen commonly detected in marine and estuarine environments. The high percentage (35%) of unassigned fungal taxa suggested the presence of a high degree of undiscovered diversity within a structured fungal community (including both yeast and filamentous life forms) and reinforce the hypothesis of a high degree of biological uniqueness of the habitat under study.
ABSTRACT
CAFE is a high-resolution spectrograph with high-precision radial velocity capabilities mounted at the 2.2 m telescope of Calar Alto Observatory. It suffered from strong degradation after ...4 yr of operations and it has now been upgraded. The upgrades of the instrument (now named CAFE2) aimed at recovering the throughput and improving the stability due to the installation of a new grating, an active temperature control in the isolated coudé room, and a new scrambling system. In this paper, we present the results of the new commissioning of the instrument and a new pipeline (CAFExtractor) that provides the user with fully reduced data including radial velocity measurements of FGK dwarf stars. The commissioning results show a clear improvement in the instrument performance. The room temperature is now stabilized down to 5 mK during one night and below 50 mK over two months. CAFE2 now provides 3 m s−1 precision on the reference ThAr frames and the on-sky tests provide a radial velocity precision of 8 m s−1 during one night (for S/N > 50). The throughput of the instrument is now back to nominal values with an efficiency of around 15 per cent at 550 nm. The limiting magnitude of the instrument for a 1 h exposure and S/N = 20 is V = 15. With all these properties, CAFE enters into the small family of high-resolution spectrographs at 2–4 m telescopes capable of reaching radial velocity precisions below 10 m s−1.
Consideration of both low- and high-resolution transmission spectroscopy is key for obtaining a comprehensive picture of exoplanet atmospheres. In studies of transmission spectra, the continuum ...information is well established with low-resolution spectra, while the shapes of individual lines are best constrained with high-resolution observations. In this work, we aim to merge high- with low-resolution transmission spectroscopy to place tighter constraints on physical parameters of the atmospheres. We present the analysis of three primary transits of WASP-69 b in the visible (VIS) channel of the CARMENES instrument and perform a combined low- and high-resolution analysis using additional data from HARPS-N, OSIRIS/GTC, and WFC3/HST already available in the literature. We investigate the Na
I
D
1
and D
2
doublet, H
α
, the Ca
II
infra-red triplet (IRT), and K
I
λ
7699 Å lines, and we monitor the stellar photometric variability by performing long-term photometric observations with the STELLA telescope. During the first CARMENES observing night, we detected the planet Na
I
D
2
and D
1
lines at ~7 and ~3
σ
significance levels, respectively. We measured a D
2
/D
1
intensity ratio of 2.5 ± 0.7, which is in agreement with previous HARPS-N observations. Our modelling of WFC3 and OSIRIS data suggests strong Rayleigh scattering, solar to super-solar water abundance, and a highly muted Na feature in the atmosphere of this planet, in agreement with previous investigations of this target. We use the continuum information retrieved from the low-resolution spectroscopy as a prior to break the degeneracy between the Na abundance, reference pressure, and thermosphere temperature for the high-resolution spectroscopic analysis. We fit the Na
I
D
1
and D
2
lines individually and find that the posterior distributions of the model parameters agree with each other within 1
σ
. Our results suggest that local thermodynamic equilibrium processes can explain the observed D
2
/D
1
ratio because the presence of haze opacity mutes the absorption features.
Atlantification of Arctic ocean is causing a sharp increase in temperature and salinity around Svalbard Islands and in Kongsfjorden. Such phenomenon and the input of sediment-rich glacial meltwater ...influence salinity, water column turbidity, and light penetration with ecological implications on the microbial features. With the aim to address the temporal variability of the microbial assemblage in relation to environmental variables, a 7-day study was carried out in Kongsfjorden, in late summer 2013. Abiotic (temperature, salinity, nutrients, total suspended matter, particulate inorganic, and organic carbon) and biotic (phyto -, picophyto-, bacterio-, and virioplankton abundance and microbial respiration) parameters were investigated at a station in the inner fjord area, ca. 8.5 km away from the glacier front. Phyto-, picophyto-, and virioplankton showed low abundance. Dinoflagellates and coccolithophorids dominated the phytoplankton community while
Synechococcus
sp. the picophytoplankton alone, in relation with Atlantic water. Low virus to bacteria ratios were detected, presumably linked to the high sedimentation rates. Interesting variability for picophytoplankton with depth, virioplankton with both time and depth, and respiratory rates with time were found. Moreover, the organic matter turnover was slower on the first sampling day compared to that of the following days. Planktonic abundance depended on the variability of both hydrology (seawater mass inflow) and freshwater runoff from the glacier (relative turbidity degree). Differently, the metabolic rates of respiration appeared to be linked with the particulate carbon pool. Over 1-week study, the diverse microbial dynamics appeared to be conditioned on complex forcing, emphasizing the importance of high-resolution experiment.
Context.
Ground-based observing time is precious in the era of exoplanet follow-up and characterization, especially in high-precision radial velocity instruments. Blind-search radial velocity surveys ...thus require a dedicated observational strategy in order to optimize the observing time, which is particularly crucial for the detection of small rocky worlds at large orbital periods.
Aims.
We developed an algorithm with the purpose of improving the efficiency of radial velocity observations in the context of exoplanet searches, and we applied it to the K-dwarfs Orbited By habitable Exoplanets experiment. Our aim is to accelerate exoplanet confirmations or, alternatively, reject false signals as early as possible in order to save telescope time and increase the efficiency of both blind-search surveys and follow-up of transiting candidates.
Methods.
Once a minimum initial number of radial velocity datapoints is reached in such a way that a periodicity starts to emerge according to generalized Lomb-Scargle periodograms, that period is targeted with the proposed algorithm, named KOBEsim. The algorithm selects the next observing date that maximizes the Bayesian evidence for this periodicity in comparison with a model with no Keplerian orbits.
Results.
By means of simulated data, we proved that the algorithm accelerates the exoplanet detection, needing 29-33% fewer observations and a 41–47% smaller time span of the full dataset for low-mass planets (
m
p
< 10
M
⊕
) in comparison with a conventional monotonic cadence strategy. For 20
M
⊕
planets we found a 16% enhancement in the number of datapoints. We also tested KOBEsim with real data for a particular KOBE target and for the confirmed planet HD 102365 b. These two tests demonstrate that the strategy is capable of speeding up the detection by up to a factor of 2 (i.e., reducing both the time span and number of observations by half).
Prokaryotic microorganisms are at the base of marine food web and are sensitive to climate changes. In the Mediterranean Sea, an important link between surface water warming and microbial activities ...is hypothesized to exist on a seasonal and inter-annual scale, with high amounts of organic matter utilized by prokaryotes and recycled in warm periods. To test this hypothesis, from 1998 to 2013, the prokaryotic abundance and microbial activities (enzymatic activities, prokaryotic heterotrophic production, and respiration), together with trophic parameters (chlorophyll, particulate organic carbon, and nitrogen), were measured in the euphotic layer of the Ionian Sea (Central Mediterranean). A statistical simultaneous analysis of the environmental and prokaryotic data was performed with the aim of depicting the evolution of microbial activities and their implications in the biogeochemical cycles. Results showed that despite the large spatial and temporal variability, temperature was the main factor affecting the variability of microbial abundance and metabolism with significant differences on both seasonal and inter-annual scales. Particularly interesting is the increase of production in summer and of the respiration in winter. In spite of low levels of chlorophyll and organic carbon, an increase of prokaryotic heterotrophic production, coupled with that of alkaline phosphatase, was found. As a consequence, the increase of prokaryotic biomass was bottom-up sustained. Most of prokaryotic activities and respiration rates were significantly correlated to organic carbon pools; the process of organic matter decomposition was frequently enhanced at higher temperature, and both prokaryotic production and growth efficiency increased in summer. In view of climate changes, the rise in temperature was associated to the increase of heterotrophic activities and this trend can have a predictive value to describe the microbial processes in the Central Mediterranean Sea.
Estimation of microbial biomass depends on cell shape and size determinations, and thus, there is a wide biovolume variability among morphotypes. Nevertheless, data on morphology and morphometry of ...prokaryotic cells under different trophic status are seldom published, due to the methodological difficulties of cell measurements. The main question addressed in this paper concerns the suitability of prokaryotic size and shape for environmental characterization. Microbial biovolumes were compared among different ecosystems, located in temperate and tropical regions. Samples were taken from fresh, brackish, mixohaline, and estuarine waters that were classified as oligo-, meso-, eu-, and hypertrophic by comparing synoptically different trophic indices. Prokaryotic cell abundance and volume were quantified by Image Analysis, used to calculate biomass, and correlated to environmental variables. Some samples were analyzed by flow cytometry also, and data from sub-populations with a different apparent DNA content were available. Prokaryotic abundances generally increased from oligo- to hypertrophic waters while cell volumes increased from oligotrophic to eutrophic waters. Although significant correlations between cell volumes and environmental variables were detected (positive with salinity and negative with Chlorophyll-
a
), different morphotypes dominated each studied regions. Our results sustain the hypothesis that prokaryotic cell size and shape could be useful to ecosystem characterization.
Context. The CARMENES survey is a high-precision radial velocity (RV) programme that aims to detect Earth-like planets orbiting low-mass stars. Aims. We develop least-squares fitting algorithms to ...derive the RVs and additional spectral diagnostics implemented in the SpEctrum Radial Velocity AnaLyser (SERVAL), a publicly available python code. Methods. We measured the RVs using high signal-to-noise templates created by coadding all available spectra of each star. We define the chromatic index as the RV gradient as a function of wavelength with the RVs measured in the echelle orders. Additionally, we computed the differential line width by correlating the fit residuals with the second derivative of the template to track variations in the stellar line width. Results. Using HARPS data, our SERVAL code achieves a RV precision at the level of 1 m/s. Applying the chromatic index to CARMENES data of the active star YZ CMi, we identify apparent RV variations induced by stellar activity. The differential line width is found to be an alternative indicator to the commonly used full width half maximum. Conclusions. We find that at the red optical wavelengths (700–900 nm) obtained by the visual channel of CARMENES, the chromatic index is an excellent tool to investigate stellar active regions and to identify and perhaps even correct for activity-induced RV variations.
We report the discovery of two planetary systems, namely G 264–012, an M 4.0 dwarf with two terrestrial planets (Mb sin i=2.50−0.30+0.29 M⊕ and Mc sin i=3.75−0.47+0.48 M⊕), and Gl 393, a bright M 2.0 ...dwarf with one terrestrial planet (Mb sini = 1.71 ± 0.24M⊕). Although both stars were proposed to belong to young stellar kinematic groups, we estimate their ages to be older than about 700 Ma. The two planets around G 264–012 were discovered using only radial-velocity (RV) data from the CARMENES exoplanet survey, with estimated orbital periods of 2.30 d and 8.05 d, respectively.Photometric monitoring and analysis of activity indicators reveal a third signal present in the RV measurements, at about 100 d,caused by stellar rotation. The planet Gl 393 b was discovered in the RV data from the HARPS, CARMENES, and HIRES instruments. Its identification was only possible after modelling, with a Gaussian process (GP), the variability produced by the magnetic activity of the star. For the earliest observations, this variability produced a forest of peaks in the periodogram of the RVs at around the 34 d rotation period determined from Kepler data, which disappeared in the latestepochs. After correcting for them with this GP model, a significant signal showed at a period of 7.03 d. No significant signals in any of our spectral activity indicators or contemporaneous photometry were found at any of the planetary periods. Given the orbital and stellar properties, the equilibrium temperatures of the three planets are all higher than that for Earth. Current planet formation theories suggest that these two systems represent a common type of architecture. This is consistent with formation following the core accretion paradigm.
Microbial processes involved in water biogeochemistry are linked to physical and chemical variability of water masses. While the occurrence of hydrological changes in the Eastern Mediterranean Sea ...has been documented, its effects on microbial dynamics and processes have been poorly investigated. An interdisciplinary survey was carried out in November 2011 to depict recent scenarios in the Ionian Mediterranean Sea. This study provides a snapshot of the hydrology and biogeochemistry of this basin, with particular emphasis on the abyssal waters, where two cores of the Eastern Mediterranean Deep Water, both of Adriatic origin, were found. The first core, located at about 3000 m, overlies the second one, which has a recent origin. Both water masses have Adriatic origin and the upper one is older than the lower one. A novel approach has been adopted to relate changes in microbial abundance and metabolism to new thermohaline and biogeochemical findings. A close relationship between surface processes driven by air–sea interaction, microbial variables, physical and chemical parameters (nutrients, dissolved organic carbon and oxygen) was observed. Being intimately coupled to DOC patterns, the microbial respiratory activity was likely the most responsive microbial parameter to hydrological changes, confirming this variable as a sentinel of environmental changes.
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