A full decade (2009-2019) of continuous nightglow observations from the NUV to the NIR

<p>The airglow emission of the mesopause region comprises molecular bands and atomic lines in the near-ultraviolet to the near-infrared wavelength range, e.g. the prominent roto-vibrational OH bands, a weak FeO/NiO continuum, the green OI line, the NaD doublet and some others. Since ground-based astronomical facilites observe through the Earth's atmosphere, the fingerprint of these emissions is visible in astronomical spectra taken with a telescope.<br>We have assembled a comprehensive data set of about 100,000 spectra in total taken between 1st of October 2009 and 30th of September 2019 with the X-shooter spectrograph, which is mounted at the Very Large Telescope in the Chilean Atacama desert (24.6°S, 70.4°W). This instrument provides medium-resolution spectra covering the entire wavelength range from 0.3 to 2.5μm simultaneously by incorporating three spectral subranges (UVB: 0.3-0.56μm; VIS: 0.56-1.02μm; NIR: 1.02-2.5μm).</p><p>The X-shooter instrument was continuously in operation during the covered period and frequently used by astronomers. Thus, the temporal coverage of the available observations is very dense for astronomical data allowing various airglow studies on time scales from minutes to a full decade. Due to the simultaneously observed wide wavelength range, individual airglow emitters as well as correlations between them can be investigated in detail (cf. Noll et al. 2021, this session, for more information).</p><p>In this presentation we describe the properties and the calibration of this unique data set.</p>

Strong Hα emission in the young planetary mass companion 2MASS J0249−0557 c

Aims. Our objective is the optical and near-infrared spectroscopic characterisation of 2MASS J0249−0557 c, a recently discovered young planetary mass companion to the β Pictoris (~25 Myr) member 2MASS J0249−0557. Methods. Using the Visible and Infrared Survey Telescope for Astronomy Hemisphere Survey and the Two Micron All Sky Survey (2MASS) data, we independently identified the companion 2MASS J0249−0557 c. We also obtained low-resolution optical spectroscopy of this object using the Optical System for Imaging and low-intermediate-Resolution Integrated Spectroscopy spectrograph at the Gran Telescopio Canarias, and near-infrared spectroscopy using the Son of Isaac spectrograph on the New Technology Telescope. Results. We classified 2MASS J0249−0557 c with a spectral type of L2.5 ± 0.5 in the optical and L3 ± 1 in the near-infrared. We identified several spectroscopic indicators of youth both in the optical and in the near-infrared that are compatible with the age of the β Pictoris moving group: strong absorption due to oxides, weak alkaline atomic lines, and a triangular shape of the H-band pseudo-continuum. We also detect a strong Hα emission, with a pseudo-equivalent width (pEW) of −90−40+20 Å, which seems persistent at timescales from several days to a few years. This indicates strong chromospheric activity or disk accretion. Although many M-type brown dwarfs have strong Hα emission, this target is one of the very few L-type planetary mass objects in which this strong Hα emission has been detected. Lithium absorption at 6708 Å is observed with pEW ≲5 Å. We also computed the binding energy of 2MASS J0249−0557 c and obtained an (absolute) upper limit of U = (−8.8 ± 4.4) × 1032 J. Conclusions. Similarly to other young brown dwarfs and isolated planetary mass objects, strong Hα emission due to accretion or chromospheric activity is also present in young planetary mass companions at ages of some dozen million years. We also found that 2MASS J0249−0557 c is one of the wide substellar companions with the lowest binding energy known to date.

WASP-127b: a misaligned planet with a partly cloudy atmosphere and tenuous sodium signature seen by ESPRESSO

Context. The study of exoplanet atmospheres is essential for understanding the formation, evolution, and composition of exoplanets. The transmission spectroscopy technique is playing a significant role in this domain. In particular, the combination of state-of-the-art spectrographs at low- and high-spectral resolution is key to our understanding of atmospheric structure and composition. Aims. We observed two transits of the close-in sub-Saturn-mass planet, WASP-127b, with ESPRESSO in the frame of the Guaranteed Time Observations Consortium. We aim to use these transit observations to study the system architecture and the exoplanet atmosphere simultaneously. Methods. We used the Reloaded Rossiter-McLaughlin technique to measure the projected obliquity λ and the projected rotational velocity veq ⋅sin(i*). We extracted the high-resolution transmission spectrum of the planet to study atomic lines. We also proposed a new cross-correlation framework to search for molecular species and we applied it to water vapor. Results. The planet is orbiting its slowly rotating host star (veq ⋅sin(i*) = 0.53−0.05+0.07 km s−1) on a retrograde misaligned orbit (λ = −128.41−5.46+5.60 °). We detected the sodium line core at the 9-σ confidence level with an excess absorption of 0.34 ± 0.04%, a blueshift of 2.74 ± 0.79 km s−1, and a full width at half maximum of 15.18 ± 1.75 km s−1. However, we did not detect the presence of other atomic species but set upper limits of only a few scale heights. Finally, we put a 3-σ upper limit on the average depth of the 1600 strongest water lines at equilibrium temperature in the visible band of 38 ppm. This constrains the cloud-deck pressure between 0.3 and 0.5 mbar by combining our data with low-resolution data in the near-infrared and models computed for this planet. Conclusions. WASP-127b, with an age of about 10 Gyr, is an unexpected exoplanet by its orbital architecture but also by the small extension of its sodium atmosphere (~7 scale heights). ESPRESSO allows us to take a step forward in the detection of weak signals, thus bringing strong constraints on the presence of clouds in exoplanet atmospheres. The framework proposed in this work can be applied to search for molecular species and study cloud-decks in other exoplanets.

Elemental abundances of M dwarfs based on high-resolution near-infrared spectra: Verification by binary systems

ABSTRACT M dwarfs are prominent targets of planet search projects, and their chemical composition is crucial to understanding the formation process or interior of orbiting exoplanets. However, measurements of elemental abundances of M dwarfs have been limited due to difficulties in the analysis of their optical spectra. We conducted a detailed chemical analysis of five M dwarfs (Teff ∼ 3200–3800 K), which form binary systems with G/K-type stars, by performing a line-by-line analysis based on high-resolution (R ∼ 80000) near-infrared (960–1710 nm) spectra obtained with CARMENES (Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical Échelle Spectrographs). We determined the chemical abundances of eight elements (Na, Mg, K, Ca, Ti, Cr, Mn, and Fe), which are in agreement with those of the primary stars within measurement errors (∼0.2 dex). Through the analysis process, we investigated the unique behavior of atomic lines in a cool atmosphere. Most atomic lines are sensitive to changes in the abundance of not only the corresponding elements but also other elements, especially dominant electron donors such as Na and Ca. The Ti i lines show a negative correlation with the overall metallicity at Teff < 3400 K due to the consumption of neutral titanium by the formation of TiO molecules. These findings indicate that to estimate the overall metallicity or the abundance of any element correctly, we need to determine the abundances of other individual elements consistently.

Analysis of the TiO isotopologues in stellar optical spectra

Context. We used the new ExoMol TiO rovibronic line lists to identify and model TiO isotopologue features in spectra of M dwarfs. Aims. We investigate problems involving the computation of electronic bands for different isotopologues of TiO by modelling optical spectra of late-type stars. Based on this, we determine their Ti isotopic abundances and compare the TiO isotopologue spectra computed using line lists by different authors. Methods. We fitted theoretical synthetic spectra to the observed stellar molecular bands of TiO. We modelled spectra of two M dwarfs, GJ 15A (M1V) and GJ 15B (M3 V), to determine Ti isotopic ratios in their atmospheres. Results. We demonstrate the accuracy of the ExoMol TOTO line list for different isotopologues of TiO and the possibility of determining accurate Ti isotope abundances in a number of spectral ranges. The 7580–7594 Å spectral range seems particularly useful, with two atomic lines of Fe I and molecular band heads of 50Ti O, 49Ti O, 48Ti O, and 47Ti O clearly observable in our two M-dwarf spectra. We determine non-solar Ti isotopic ratios of 46Ti, 47Ti, 48Ti, 49Ti, and 50Ti of 7.9, 5.2, 72.8, 7.9, and 6.2 for GJ 15A and 7.4, 4.2, 76.6, 5.8, and 6.0 for GJ 15B with an accuracy of ±0.2. [Ti] = 0.040 and 0.199 and within an accuracy of ±0.10 were also determined for GJ 15A and GJ 15B, respectively. Conclusions. We find that the ExoMol TOTO TiO line list (a) describes the fine details in line position and intensity of the M-dwarf spectra better than other available TiO line lists, (b) correctly reproduces the positions and intensities of the TiO isotopologue band heads observed in M-dwarf spectra, and (c) can be used to determine Ti isotope abundances in atmospheres of M stars.

Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS)

Context. WASP-121 b is a hot Jupiter that was recently found to possess rich emission (day side) and transmission (limb) spectra, suggestive of the presence of a multitude of chemical species in the atmosphere. Aims. We survey the transmission spectrum of WASP-121 b for line-absorption by metals and molecules at high spectral resolution and elaborate on existing interpretations of the optical transmission spectrum observed with the Hubble Space Telescope (HST). Methods. We applied the cross-correlation technique and direct differential spectroscopy to search for sodium and other neutral and ionised atoms, TiO, VO, and SH in high-resolution transit spectra obtained with the HARPS spectrograph. We injected models assuming chemical and hydrostatic equilibrium with a varying temperature and composition to enable model comparison, and employed two bootstrap methods to test the robustness of our detections. Results. We detect neutral Mg, Na, Ca, Cr, Fe, Ni, and V, which we predict exists in equilibrium with a significant quantity of VO, supporting earlier observations by HST/WFC3. Non-detections of Ti and TiO support the hypothesis that Ti is depleted via a cold-trap mechanism, as has been proposed in the literature. Atomic line depths are under-predicted by hydrostatic models by a factor of 1.5 to 8, confirming recent findings that the atmosphere is extended. We predict the existence of significant concentrations of gas-phase TiO2, VO2, and TiS, which could be important absorbers at optical and near-IR wavelengths in hot Jupiter atmospheres. However, accurate line-list data are not currently available for them. We find no evidence for absorption by SH and find that inflated atomic lines can plausibly explain the slope of the transmission spectrum observed in the near-ultraviolet with HST. The Na I D lines are significantly broadened (FWHM ~50 to 70 km s−1) and show a difference in their respective depths of ~15 scale heights, which is not expected from isothermal hydrostatic theory. If this asymmetry is of astrophysical origin, it may indicate that Na I forms an optically thin envelope, reminiscent of the Na I cloud surrounding Jupiter, or that it is hydrodynamically outflowing.

The 3D non-LTE solar nitrogen abundance from atomic lines

Nitrogen is an important element in various fields of stellar and Galactic astronomy, and the solar nitrogen abundance is crucial as a yardstick for comparing different objects in the cosmos. In order to obtain a precise and accurate value for this abundance, we carried out N I line formation calculations in a 3D radiative-hydrodynamic STAGGER model solar atmosphere in full 3D non-local thermodynamic equilibrium (non-LTE). We used a model atom that includes physically motivated descriptions for the inelastic collisions of N I with free electrons and with neutral hydrogen. We selected five N I lines of high excitation energy to study in detail, based on their strengths and on their being relatively free of blends. We found that these lines are slightly strengthened from non-LTE photon losses and from 3D granulation effects, resulting in negative abundance corrections of around − 0.01 dex and − 0.04 dex, respectively. Our advocated solar nitrogen abundance is log ɛN = 7.77, with the systematic 1σ uncertainty estimated to be 0.05 dex. This result is consistent with earlier studies after correcting for differences in line selections and equivalent widths.

Химический анализ зоопланктона методом лазерно-искровой эмиссионной спектроскопии без использования образцов сравнения

This study deals with the determination of ratios of light metals (Li, Na, K, Mg, and Ca) in zooplankton (Calanus spp.) by calibration free laser-induced breakdown spectroscopy, assuming local thermodynamic equilibrium. The temperature of laser-induced plasma of zooplankton was derived from rotation-vibration bands of CN, and the electron density was calculated by Stark broadening of Mg I 383.23 nm, Li I 610.37 nm, and Ca II 396.85 nm lines. The synthetic spectra calculated with a radiation transport model for the experimental values of T and Ne were used for a selection of analytical atomic lines free from self-absorption. We compared the obtained data with the results of atomic emission and mass spectrometry with inductively coupled plasma. We also discussed the influence of ionization equilibrium on the accuracy of the results. We propose the presented method for direct semi-quantitative determination of Li, Mg, and Ca ratios in zooplankton.