Hydrogen Lines Research Articles

The Impact of Partial Solar Eclipse on the Observation of Neutral Hydrogen Emission Line

The Impact of Partial Solar Eclipse on the Observation of Neutral Hydrogen Emission Line

Simulations of Cryogenic Line Chilldown with Advanced Subgrid Wall Boiling Models

A mesoscale model for boiling processes in water was adapted for cryogens and demonstrated for chilldown of propellant transfer lines in both liquid nitrogen and hydrogen. The subgrid boiling model accurately captures the contributions to heat transfer from the generation of bubble nuclei, growth, and interaction of the bubbles in the microlayer as well as quenching of the boiling surface following bubble departure. It was adapted for cryogenic fluids using thermodynamic scaling concepts, considering nondimensional pressures and temperatures that are scaled by the corresponding critical values for the fluid. The boiling model was demonstrated for line chilldown in liquid nitrogen. The predicted wall temperature at which quenching occurs was close to the test data for liquid nitrogen, while the slope of the temperature curve after quenching is initiated shows a steeper variation than the test data. Simulations were also performed for liquid hydrogen. Chilldown times in liquid hydrogen are much more rapid due to higher heat transfer in the film boiling regime, and accurately modeling the impact of turbulent heat transfer was found to be important. Furthermore, due to the much colder fluid temperatures in liquid hydrogen, it is critical to model the variable thermal properties of the solid material.

An in-situ investigation of microstructure neighborhood effects on hydrogen-induced dislocation activity

The interactions between hydrogen and crystallographic defects are the key to understanding hydrogen induced localized plasticity or damage mechanisms. However, unraveling such interactions based on the resulting mechanical effects alone can be challenging, due to the spectrum of various effects hydrogen can create in a given microstructure. Pre-deformation or post-mortem characterization of hydrogen segregation has similar limitations, as they can only provide snapshots of these complex processes with challenging spatial and temporal scales. To tackle this, we design in situ experiments that combine electron channeling contrast imaging (ECCI), electron backscattered diffraction (EBSD), and desorption spectroscopy, to investigate hydrogen defect interactions, under no external loading. We show that the inhomogeneous hydrogen distribution within microstructures can cause long-range (>200 nm) dislocation rearrangements. Interpretation of these results as manifestations of boundary-segregation induced stress suggests that microstructural characteristics on either side of the boundary should also play an important role. We provide quantitative assessments of these microstructure neighborhood effects and discuss additional contributions from hydrogen-induced changes in stacking fault energy and elastic modulus.

Spectroscopic study of late-type emission-line stars using the data from LAMOST DR6

Abstract Low-mass emission-line stars belong to various evolutionary stages, from pre-main-sequence young stars to evolved stars. In this work, we present a catalog of late-type (F0 to M9) emission-line stars from the LAMOST Data Release 6. Using the scipy package, we created a Python code that finds the emission peak at H-alpha in all late-type stellar spectra. A dataset of 38,152 late-type emission-line stars was obtained after a rigorous examination of the photometric quality flags and the signal-to-noise ratio of the spectra. Adopting well-known photometric and spectroscopic methods, we classified our sample into 438 infrared excess sources, 4,669 post-main-sequence candidates, 9,718 Fe/Ge/Ke sources, and 23,264 dMe sources. From a cross-match with known databases, we found that 29,213 sources, comprising 56 IR excess sources, 7,899 Fe/Ge/Ke stars, 17,533 dMe stars, and 3,725 PtMS candidates, are new detections. We measured the equivalent width of the major emission lines observed in the spectra of our sample of emission-line stars. Furthermore, the trend observed in the line strengths of major emission lines over the entire late-type spectral range is analyzed. We further classified the sample into 4 groups based on the presence of Hydrogen and Calcium emission lines. This work presents a large dataset of late-type emission-line stars which improves the current sample to study active phenomena in late-type stars.

ALMA and GMRT Studies of Dust Continuum Emission and Spectral Lines Toward Oort Cloud Comet C/2022 E3 (ZTF)

Abstract The atomic and molecular compounds of cometary ices serve as valuable knowledge into the chemical and physical properties of the outer solar nebula, where comets are formed. From the cometary atmospheres, the atoms and gas-phase molecules arise mainly in three ways: (i) the outgassing from the nucleus, (ii) the photochemical process, and (iii) the sublimation of icy grains from the nucleus. In this paper, we present the radio and millimeter wavelength observation results of Oort cloud non-periodic comet C/2022 E3 (ZTF) using the Giant Metrewave Radio Telescope (GMRT) band L and the Atacama Large Millimeter/Submillimeter Array (ALMA) band 6. We do not detect continuum emissions and an emission line of atomic hydrogen (HI) at rest frequency 1420 MHz from this comet using the GMRT. Based on ALMA observations, we detect the dust continuum emission and rotational emission lines of methanol (CH3OH) from comet C/2022 E3 (ZTF). From the dust continuum emission, the activity of dust production (Afρ) of comet ZTF is 2280±50 cm. Based on LTE spectral modelling, the column density and excitation temperature of CH3OH towards C/2022 E3 (ZTF) are (4.50±0.25)×10^{14} cm^{−2} and 70±3 K. The integrated emission maps show that CH3OH was emitted from the coma region of the comet. The production rate of CH3OH towards C/2022 E3 (ZTF) is (7.32±0.64)×10^{26} molecules s^{−1}. The fractional abundance of CH3OH with respect to H2O in the coma of the comet is 1.52%. We also compare our derived abundance of CH3OH with the existence modelled value, and we see the observed and modelled values are nearly similar. We claim that CH3OH is formed via the subsequential hydrogenation of formaldehyde (H2CO) on the grain surface of comet C/2022 E3 (ZTF).

Molecular Hydrogen Line Identifications in Solar Flares Observed by IRIS: Lower Atmospheric Structure from Radiometric Analysis

A rich spectrum of molecular hydrogen (H2) emission lines is seen in sensitive observations from the far-ultraviolet (FUV) channels of the Interface Region Imaging Spectrograph (IRIS) during flare activity in solar active region NOAA Active Region 11861. Based on this observation, we have determined 37 new line identifications by comparing synthetic spectra produced using 1D modeling of H2 fluorescence. To avoid misidentification of the H2 lines, we have also compiled a complete list of atomic line identifications for the IRIS FUV bandpasses from previous work. We carry out analysis of the spatially resolved H2 emission that occurs during the flares and find the following: (1) in spatially resolved observations the H2 line ratios may show optically thick line formation, contrary to previous results; (2) comparison of the spatial distribution of H2 Doppler velocities with those measured from other species reveals that H2 remote sensing probes an intermediate depth in the atmosphere between the photosphere and chromosphere, consistent with expectations from modeling; (3) the relationship between H2 line intensity and the observed intensity of its exciter is related to the atmospheric stratification; however, (4) H2 fluorescence can sometimes occur in response to radiation from distant sources many megameters away across the solar surface.

The ANTARESS workflow

High-resolution spectrographs open a detailed window onto the atmospheres of stars and planets. As the number of systems observed with different instruments grows, it is crucial to develop a standard in analyzing spectral time series of exoplanet transits and occultations, for the benefit of reproducibility. Here, we introduce the ANTARESS workflow, a set of methods aimed at processing high-resolution spectroscopy datasets in a robust way and extracting accurate exoplanetary and stellar spectra. While a fast preliminary analysis can be run on order-merged 1D spectra and cross-correlation functions (CCFs), the workflow was optimally designed for extracted 2D echelle spectra to remain close to the original detector counts, limit the spectral resampling, and propagate the correlated noise. Input data from multiple instruments and epochs were corrected for relevant environmental and instrumental effects, processed homogeneously, and analyzed independently or jointly. In this first paper, we show how planet-occulted stellar spectra extracted along the transit chord and cleaned from planetary contamination provide a direct comparison with theoretical stellar models and enable a spectral and spatial mapping of the photosphere. We illustrate this application of the workflow to archival ESPRESSO data, using the Rossiter-McLaughlin effect Revolutions (RMR) technique to confirm the spin-orbit alignment of HD 209458b and unveil biases in WASP-76b’s published orbital architecture. Because the workflow is modular and its concepts are general, it can support new methods and be extended to additional spectrographs to find a range of applications beyond the proposed scope. In a companion paper, we will present how planet-occulted spectra can be processed further to extract and analyze planetary spectra decontaminated from the star, providing clean and direct measurements of atmospheric properties.

ExoplaNeT accRetion mOnitoring sPectroscopic surveY (ENTROPY)

Context. Accretion among planetary mass companions is a poorly understood phenomenon, due to the lack of both observational and theoretical studies. The detection of emission lines from accreting gas giants facilitates detailed investigations into this process. Aims. This work presents a detailed analysis of Balmer lines from one of the few known young, planetary-mass objects with observed emission, the isolated L2γ dwarf 2MASS J11151597+1937266 with a mass between 7 and 21 MJup and an age of 5–45 Myr, located at 45 ± 2 pc. Methods. We obtained the first high-resolution (R ~ 50 000) spectrum of the target with VLT/UVES, an echelle spectrograph operating in the near-ultraviolet to visible wavelengths (3200–6800 Å). Results. We report several resolved hydrogen (H I; H3–H6) and helium (He I; λ5875.6) emission lines in the spectrum. Based on the asymmetric line profiles of Hα and Hβ, the 10% width of Hα (199 ± 1 km s−1), tentative He I λ6678 emission, and indications of a disk from mid-infrared excess, we confirm ongoing accretion at this object. Using the Gaia update of the parallax, we revise its temperature to 1816 ± 63 K and radius to 1.5 ± 0.1 RJup. Analysis of observed H I profiles using a 1D planet-surface shock model implies a pre-shock gas velocity, v0 = 120−40+ 80 km s−1, and a pre-shock density, log(n0/cm−3) = 14−5+ 0. The pre-shock velocity points to a mass, Mp = 6−4+ 8 MJup, for the target. Combining H I line luminosities (Lline) and planetary Lline−Lacc (accretion luminosity) scaling relations, we derived a mass accretion rate, Ṁacc = 1.4−0.9+ 2.8 × 10−8 MJup yr−1. Conclusions. The line-emitting area predicted from the planet-surface shock model is very small (~0.03%), and points to a shock at the base of a magnetospherically induced funnel. The Hα profile exhibits a much stronger flux than predicted by the model that best fits the rest of the H I profiles, indicating that another mechanism than shock emission contributes to the Hα emission. Comparison of line fluxes and Ṁacc from archival moderate-resolution SDSS spectra indicate variable accretion at 2MASS J11151597+1937266.

Laser-induced plasma analysis of ammonia-oxygen and ammonia-oxygen-enriched-air flames at elevated pressures

This study employed Laser-induced breakdown spectroscopy (LIBS) to measure the fuel-oxidizer ratio (FOR) of ammonia combustion with oxygen-enriched air and pure oxygen flames at elevated pressures (100 - 300 kPa). The correlations between the spectral line intensity ratios of nitrogen (N), hydrogen (H), oxygen (O), and equivalence ratio were used to quantify the FOR of flames at various pressures. The effect of pressure on the stability and precision of the calibration profiles for the elemental intensity ratios in flames was investigated. It was observed that the H/O correlation decreases with pressure increase for both ammonia flames. N/O correlations decrease with elevated pressure for the ammonia-oxygen flame. Furthermore, the nitrogen (NII) spectral emission lines at 568 nm and 595 nm were used to estimate the plasma temperature, while the hydrogen (Hα) line at 656 nm was used for electron number density measurements.

Secrets in the shadow: High precision stellar abundances of fast-rotating A-type exoplanet host stars through transit spectroscopy

The spectra of fast-rotating A-type stars have strongly broadened absorption lines. This effect causes blending of the absorption lines, hindering the measurement of the abundances of the elements that are in the stellar photosphere. As the exoplanet transits across its host star, it obscures the stellar spectrum that is emitted from directly behind the planet. We aim to extract this obscured spectrum because it is less affected by rotational broadening, resolving the blending of weak lines of elements that would otherwise remain inaccessible. This allows us to more precisely measure the metal abundances in ultra-hot Jupiter systems, many of which have fast-rotating host stars. We developed a novel method that isolates the stellar spectra behind the planet during a spectral time series, and reconstructs the disc-integrated non-broadened spectrum of the host star. We have systematically tested this method with model-generated spectra of the transit of WASP-189 b across its fast-rotating A-type host star, assessing the effects of limb-darkening, the choice of absorption lines, and the signal-to-noise regime; and demonstrating the sensitivity to photospheric parameters ($T_ eff $ and log $g$) and elemental abundances. We applied the method to observations by the HARPS high-resolution spectrograph. For WASP-189, we obtain the metallicity and photospheric abundances for several species previously not reported in literature, Mg, Ca, and Ti, with a significantly improved accuracy compared to the ordinary broadened stellar spectrum. This method can be generally applied to other transiting systems in which abundance determinations via spectral synthesis are imprecise due to severe line blending. It is important to accurately determine the photospheric properties of exoplanet host stars, as it can provide further insight into the formation and evolution of the planets.

Strong He i Emission Lines in High N/O Galaxies at z ∼ 6 Identified in JWST Spectra: High He/H Abundance Ratios or High Electron Densities?

We present He i/Hβ flux and He/H abundance ratios in three James Webb Space Telescope galaxies with significant constraints on N/O abundance ratios, GS-NDG-9422, RXCJ2248-ID, and GLASS150008 at z ∼ 6 mostly with the spectroscopic coverage from He i λ4471 and He ii λ4686 to He i λ7065, and comparing with 68 local dwarf galaxies. We find that these high-z galaxies present strong He i emission with He i/Hβ flux ratios generally larger than those of local dwarf galaxies. We derive He/H with all of the detected Hei, He ii, and 2−3 hydrogen Balmer lines in the same manner as the local He/H determination conducted for cosmology studies. These high-z galaxies show He overabundance He/H ≳0.10 or high electron density of n e ∼ 103−4 cm−3 much larger than local values at low O/H, 12+log(O/H)=7−8 . In contrast, we obtain low He/H and n e values for our local dwarf galaxies by the same technique with the same helium and hydrogen lines, and confirm that the difference between the high-z and local dwarf galaxies is not mimicked by systematics. While two scenarios of (1) He overabundance and (2) high electron density are not clearly concluded, we find that there is a positive correlation between the He/H–N/O or n e–N/O plane by the comparison of the high-z and local dwarf galaxies. Scenario (1) suggests that the overabundant helium and nitrogen are not explained by the standard chemical enrichment of core-collapse supernovae, but by the CNO-cycle products and equilibrium ratios, respectively. Scenario (2) indicates that the strong helium lines originated from the central dense clouds of the high-z galaxies by excessive collisional excitation.

Retrieving hourly aerosol optical depth for geostationary satellite FY-4B/AGRI by surface-related dynamic spectral reflectance ratio method

The Advanced Geostationary Radiation Imager (AGRI) on board Fengyun-4B (FY-4B) has been found to have significant advantages in aerosol dynamic monitoring. This study proposed a surface-related dynamic spectral reflectance ratio (SDSRR) method for FY-4B AGRI to solve the problem of inaccurate surface reflectance estimation in Aerosol Optical Depth (AOD) retrieval. This method introduced Moderate-resolution Imaging Spectroradiometer (MODIS) aerosol product to assist in calculating the surface reflectance of the AGRI blue channel and the spectral reflectance ratio between the shortwave infrared (SWIR) channel and the blue channel, then constructed a surface-related dynamic spectral reflectance ratio series by combining the spectral reflectance ratio, Normalized Difference Vegetation Index (NDVI) and Scattering Angle (SCA) to obtain aerosol retrieval results. To verify the accuracy of the SDSRR method, the AOD dataset of the SDSRR method, the official aerosol products of AGRI (LDA) and Advanced Himawari Imager (AHI) AOD datasets were compared with the ground-based observations of Aerosol Robotic Network (AERONET) and Sun-shy radiometer Observation Network (SONET) in East Asia. The results indicate that the SDSRR method performs more consistently in East Asia compared to the official ARGI aerosol products. The root-mean-square-error (RMSE), mean error (ME), and correlation coefficient (R) between SDSRR AOD and ground-based measurements are 0.286, 0.180 and 0.70, which is better than that of LDA AOD (RMSE = 0.508, ME = 0.292, R = 0.69). Additionally, the RMSE, ME, and R of AHI AOD were 0.253, 0.168, and 0.74, respectively.

Emergence hour-by-hour of r-process features in the kilonova AT2017gfo

The spectral features in the optical/near-infrared counterparts of neutron star mergers (kilonovae, KNe) evolve dramatically on hourly timescales. To examine the spectral evolution, we compiled a temporal series that was complete at all observed epochs from 0.5 to 9.4 days of the best optical/near-infrared (NIR) spectra of the gravitational-wave detected kilonova AT2017gfo. Using our analysis of this spectral series, we show that the emergence times of spectral features place strong constraints on line identifications and ejecta properties, while their subsequent evolution probes the structure of the ejecta. We find that the most prominent spectral feature, the 1 μm P Cygni line, appears suddenly, with the earliest detection at 1.17 days. We find evidence in this earliest feature for the fastest yet discovered kilonova ejecta component at 0.40–0.45c. Across the observed epochs and wavelengths, the velocities of the line-forming regions span nearly an order of magnitude, down to as low as 0.04–0.07c. The time of emergence closely follows the predictions for Sr II because Sr III combines rapidly under local thermal equilibrium (LTE) conditions. The transition time between the doubly and singly ionised states provides the first direct measurement of the ionisation temperature. This temperature is highly consistent with the temperature of the emitted blackbody radiation field at a level of a few percent. Furthermore, we find the KN to be isotropic in temperature, that is, the polar and equatorial ejecta differ by less than a few hundred Kelvin or ≲5%, in the first few days post-merger based on measurements of the reverberation time-delay effect. This suggests that a model with very simple assumptions, with single-temperature LTE conditions, reproduces the early kilonova properties surprisingly well.

Two-step synthesis of ionic liquid demulsifiers for demulsification of water-in-oil emulsion

Stabilized water-in-oil emulsions present significant challenges for oil production. However, current demulsifiers often face limitations such as high demulsification temperatures, low efficiencies, and complex synthesis processes, making the resolution of this challenge a demanding task. In this study, we successfully synthesized two ionic liquid demulsifiers, PEDA-Br and GEDA-Br, employing a straightforward two-step procedure. The objective was to enable effective treatment of water-in-oil emulsions at low temperatures with high efficiency. The structure of the demulsifiers was characterized utilizing Fourier-transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance hydrogen spectra (1H NMR). Bottle tests were then conducted to evaluate their demulsification efficiency (DE) in water-in-oil (W/O) emulsions. The results demonstrated that GEDA-Br achieved a DE of 98.92 % at a concentration of 500 mg/L and a temperature of 50 °C after 2 h. Additionally, both PEDA-Br and GEDA-Br exhibited DE values exceeding 95 % at a salinity level of 10,000 mg/L, and both proved effective across a broad pH range of 4 to 12. These findings highlight their robust resistance to high salinity and both acidic and alkaline conditions. The study also examined the demulsification mechanism in terms of interfacial tension (IFT), elastic modulus of the interfacial film, three-phase contact angle (TCA), and microscopic observations. The excellent interfacial activity, ability to reduce interfacial tension, and electrostatic neutralization capability are responsible for its outstanding demulsification performance.

Direct determination of lithium in brine samples using handheld LIBS without sample treatment: sample introduction by venturi system.

Splashing is the main problem for the direct analysis of aqueous samples using LIBS since it generates serious precision and accuracy issues. This study demonstrates the direct determination of Li content in brines for the control of industrial mining processes using a portable LIBS device based on the direct laser impact on the sample, without any sample treatment, through the design of a sample injection system based on the Venturi effect. Our results demonstrated that the utilization of the 653.3 nm hydrogen line as an internal standard reduces the model calibration fitting error from 0.440 root mean square error in a standard calibration curve to 0.123 on the internal standard curve. Conversely, the development of a Venturi effect-based injection device using compressed air converts the brine into a fine mist which decrease splashing, resulting in an up to 10-fold error reduction, all without the necessity of employing an internal standard. Our results, evaluated by comparing them to the ASTM D3561-11 standard method using flame atomic absorption spectrometry, indicate that it is feasible to determine the lithium content in brine samples with an error of under 20% and a detection limit of 13 mg kg-1.

He II line intensity measurements in the JET tokamak

Abstract An understanding of the behaviour of the D or He fuel used in tokamak discharges is essential in analyses such as modelling edge and divertor transport and the erosion of the vessel walls. However, poor agreement is found between measurements made on the JET tokamak and collisional-radiative models used to predict the hydrogen-like D and He line intensities. The range of temperatures of the plasmas emitting the radiation is also limited, in contrast to that for many impurities for which a wide range is possible. This is particularly so for He II whose line intensities tend to have the same near-constant ratios in most pulses, suggesting that the emission originates in plasma regions with very similar electron temperatures. To gain understanding and to allow quantitative comparisons with theoretical models, extensive observations of the VUV Lyman series have been made, for all discharge scenarios run during three He campaigns. Those for He discharges in both JET ITER-like wall (JET-ILW) and JET C (JET-C) campaigns are presented here. He discharges have the advantage of fewer impurities resulting in less complex spectra than when D is used as the fuel. However, the characteristics of the observed discrepancies are similar in both species, allowing He to be used as a proxy for D in order to gain understanding of the discrepancy. In addition, the study of He avoids the complication of molecular species contributing to the level populations. Opacity effects are also expected to be less severe in He discharges. Nevertheless, so as to ensure that the measurements are not unduly affected by opacity, comparisons have also been made with emission from Balmer and Paschen series members. Measurements of both line intensities and their ratios are presented for all-pulse surveys and for individual pulses. In exceptional cases in which the He emission is intense a dependence on the He II line intensity is demonstrated. The discrepancy between these measurements and the theoretical models is illustrated.

Analyzing JWST/NIRSpec Hydrogen Line Detections at TWA 27B: Constraining Accretion Properties and Geometry

Hydrogen lines from forming planets are crucial for understanding planet formation. However, the number of planetary hydrogen line detections is still limited. Recent JWST/NIRSpec observations have detected Paschen and Brackett hydrogen lines at TWA 27 B (2M1207b). Although classified as a planetary- mass companison (PMC) rather than a planet due to its large mass ratio to the central star, TWA 27 B’s hydrogen line emissions are expected to be same as the planetary one, given its small mass (≈5M J). We aim to constrain the accretion properties and accretion geometry of TWA 27 B, contributing to our understanding of hydrogen-line emission mechanisms common to both PMCs and planets. We conduct spectral fitting of four bright hydrogen lines (Pa-α, Pa-β, Pa-γ, Pa-δ) with an accretion-shock emission model tailored for forming planets. We estimate the mass accretion rate at Ṁ≈3×10−9MJyr−1 with our fiducial parameters, though this is subject to an uncertainty of up to factor of ten. Our analysis also indicates a dense accretion flow, n ≳ 1013 cm−3 just before the shock, implying a small accretion-shock filling factor f f on the planetary surface (f f ≲ 5 × 10−4). This finding suggests that magnetospheric accretion is occurring at TWA 27 B. Additionally, we carry out a comparative analysis of hydrogen-line emission color to identify the emission mechanism, but the associated uncertainties proved too large for definitive conclusions. This underscores the need for further high-precision observational studies to elucidate these emission mechanisms fully.

Modification mechanism of green polyurethane modified asphalt prepared by in-situ polymerization

In order to investigate the modification mechanism of green polyurethane (PU) modified asphalt prepared by in-situ polymerization, PU was separated from PU modified asphalt (PUMA) and the molecular fragmentation information of synthesized PU and separated PU was characterized by pyrolysis-gas chromatography-mass spectrometry. The binding forms of the asphalt molecules to the PU were deduced, and the deduced structures were validated by infrared spectroscopy, nuclear magnetic hydrogen spectroscopy, gel chromatography, elemental analysis, and molecular dynamics simulation. The results showed that compared to synthetic PU, the PU molecular fragments separated from modified asphalt additionally contained active asphalt components. Meanwhile, infrared and hydrogen spectra verified that the active components in the asphalt can chemically with -NCO in the PU prepolymer. The extension of curing time led to more combinations of asphalt molecules and PU prepolymers, which were manifested in the increases of the element contents of C, O, and S and the increase of molecular weight of PU separated from PUMA. The chain extender could not be completely reacted during the preparation and curing of PUMA and after curing for 6 months, the binding rate of PU prepolymer and chain extender was 24.80 %. PU prepolymer can react with the moisture in the air to generate amine group, and further generates urea group during the preparation and curing of PUMA. This work serves as a reference for the design and preparation of PUMA by in-situ polymerization.

Probing proton-to-electron mass ratio variability with QSO 0347–383 spectra

We introduce a new approach for detecting potential cosmological changes in the proton-to-electron mass ratio (µ) by studying the absorption lines of molecular hydrogen (H2) in the high-redshift quasar QSO 0347–383. By comparing these observations with high-precision laboratory data, we determine a variation of ∆µ/µ = (0.120 ± 0.144) × 10−8 at zabs = 3.025. This highly precise result offers valuable insights into the constancy of fundamental physical constants over extended cosmic periods.

Assessing the phenological state of evergreen conifers using hyperspectral imaging time series

Phenology is a reliable indicator of vegetation condition and ecological changes in the environment. Plant Spectral Phenology (PSP) offers the potential for the development of automated, rapid, and wide-area vegetation monitoring systems. The spectral characteristics of plants (vegetation) are employed as metrics of PSP, which can be sensed both proximally and remotely. A key objective is to undertake a comparative analysis of the results of PSP versus those of phenology based on visual observations. The resolution of this issue is of paramount importance for the coordination of phenological studies at diverse levels (ground, surface, and remote), thus ensuring the continuity of phenological studies conducted prior to the advent of PSP. This issue is particularly pronounced in the case of evergreen conifers. The present study focuses on four evergreen conifers: Thuja occidentalis, Platycladus orientalis, Pinus sylvestris and P. nigra subsp. pallasiana. Hyperspectral imaging was performed under laboratory conditions using a Cubert UHD-185 hyperspectral camera. Concomitantly, phenological observations were conducted. The spectral time series yielded 79 chlorophyll-sensitive and carotenoid-sensitive Vegetation Indices (VIs), which were then used to construct double logistic functions. A significant proportion of the VIs exhibited a high degree of correctness with regard to the aforementioned functions, as indicated by the value of R2 exceeding 0.7. The values of the principal stages of seasonal development of evergreen conifers, namely the Start of Season (SOS), End of Season (EOS), Position of Peak value (POP) and Length of Season (LOS), were calculated using double logistic functions. These stages were matched to the phenological phases of development of the experimental plants. The values of SOS, EOS, POP and LOS varied significantly depending on the VIs used as a metric as well as the evergreen conifers. The lowest variability by metrics is observed in SOS, while the maximum is observed in EOS and POP. The results obtained may be of importance for the choice of criterion for the comparison of PSP with phenology based on visual observations and the most suitable VIs for these purposes.