OH Lines Research Articles

Tomato SlPUB24 enhances resistance to Xanthomonas euvesicatoria pv. perforans race T3

Solanum lycopersicum var. cerasiforme accession PI 114490 has broad-spectrum resistance to bacterial spot caused by several species of Xanthomonas. Resistance is quantitatively inherited, and a common quantitative trait locus QTL-11B on chromosome 11 has been identified previously. In this study, the SlPub24 gene was characterized in QTL-11B. SlPub24 in PI 114490 was upregulated by infection with X. euvesicatoria pv. perforans race T3, but its transcription was low in the susceptible line OH 88119 whether or not it was infected by the pathogen. The differential expression of SlPub24 between PI 114490 and OH 88119 was due to great sequence variation in the promoter region. The promoter of SlPub24 in OH 88119 had very low activity and did not respond to pathogen infection. Transgenic lines of OH 88119 overexpressing SlPub24 isolated from PI 114490 showed significantly enhanced resistance, while mutants of Slpub24 generated by CRISPR/Cas9 editing showed more susceptibility to race T3 and to other races. The mutants also showed spontaneous cell death in leaves. The expression of the salicylic acid (SA) pathway gene phenylalanine ammonia-lyase (PAL) and signaling-related genes pathogenesis-related (PR1) and nonexpresser of PR1 (NPR1) were influenced by SlPub24. The content of SA in tomato plants was consistent with the level of SlPub24 expression. Furthermore, SlPUB24 interacted with the cell wall protein SlCWP and could regulate the degradation of SlCWP. The expression levels of SlCWP and SlCWINV1, a cell wall invertase gene, showed opposite patterns during pathogen infection. The activity of SlCWINV1 was lower in mutants than in PI 114490. The results are discussed in terms of the roles of the abovementioned genes, and a potential model for SlPUB24-mediated resistance to bacterial spot is proposed.

Emission spectrum analysis of an atmospheric electrode microwave discharge in argon flow and of a cold plasma jet on its base

The measurements and analysis of the emission spectra both of atmospheric-pressure electrode microwave discharge in argon flow and cold plasma jet induced by the discharge are conducted. We used experimental setup based on the previously developed multipurpose 2.45-Hz-plasmatron with the external portable discharge chamber (plasma torch) with the outlet of 2.5 cm in diameter and power of about several hundred watts. Discharge chamber has 6 rod-like electrodes which form a regular hexagon in a cross section of the torch. Discharge channels are formed between the ends of the electrodes and the inner wall of the chamber. Molecular bands of NO, OH, N2, NH and atomic lines of Ar were found in the spectrum of the discharge channels. Based on the analysis of the spectra, it was shown that the gas temperature in the discharge channel was about 1200 K. In the cold plasma jet spectrum, due to its weak luminescence, only the molecular lines OH and N2 were reliably observed.

Evolution of OH and H2O Maser Emission in the Active Star Formation Region NGC 2071

We present the observation results of the star forming region NGC 2071 in the 1.35-cm H2O line and 18-cm OH lines obtained with the 22-m radio telescope in Pushchino (Russia) and the large radio telescope in Nancay (France), respectively. The catalog of H2O maser emission spectra from December 2010 to January 2020 is given. The total flux variability for the entire monitoring period (1979–2020) has two activity cycles of close duration (approximately 20 years), which were accompanied by strong flares at intervals of one to four years. It is shown that the medium for the generation of H2O maser emission is greatly fragmented and contains small-scale turbulent motions of matter. The observed drift and radial velocity jumps of the H2O emission features can be a consequence of the complex, inhomogeneous structure of the maser emission regions. OH emission in the 1665 and 1667 MHz main lines and in the 1612 MHz satellite line in the radial velocity range of 7–12 km/s is broadband. The ratio of intensities differs from equilibrium. The substantiation of the observed ratio between the intensities of this emission and absorption in the 1720 MHz line is given. OH maser emission was observed in 2007 in the left circular polarization in the 1667 MHz line at 13.02 and 13.55 km/s with a flux density of ~0.3 Jy and a width of ~0.25 km/s for each of the velocities.

Radio properties of the OH megamaser galaxy IRAS 02524+2046

We present results from VLBI observations of continuum and OH line emission in IRAS 02524+2046 as well as arcsecond-scale radio properties of this galaxy using VLA archive data. We found that there is no significant detection of radio continuum emission from VLBI observations. The arcsecond-scale radio images of this source show no clear extended emission. The total radio flux density at L and C bands are approximately 2.9 mJy and 1.0 mJy, respectively, which indicates a steep radio spectral index between the two bands. A steep spectral index, low brightness temperature, and high q-ratio (i.e., the far-infrared to the radio flux density), which are three critical indicators in the classification of radio activity in the nuclei of galaxies, are all consistent with the classification of this source as a starburst galaxy from its optical spectrum. The high-resolution line profile reveals that we detected both the 1665 MHz and 1667 MHz OH maser lines, which show two and three clear components, respectively. The channel maps show that the maser emission are distributed in a region of ∼210 pc × 90 pc. The detected maser components in different regions indicate similar double spectral features, which might be evidence that this galaxy is at a stage of major merger as seen from the optical morphology.

Constraints on Metastable Helium in the Atmospheres of WASP-69b and WASP-52b with Ultranarrowband Photometry

Abstract Infrared observations of metastable 23S helium absorption with ground- and space-based spectroscopy are rapidly maturing, as this species is a unique probe of exoplanet atmospheres. Specifically, the transit depth in the triplet feature (with vacuum wavelengths near 1083.3 nm) can be used to constrain the temperature and mass-loss rate of an exoplanet’s upper atmosphere. Here, we present a new photometric technique to measure metastable 23S helium absorption using an ultranarrowband filter (FWHM 0.635 nm) coupled to a beam-shaping diffuser installed in the Wide-field Infrared Camera on the 200 inch Hale Telescope at Palomar Observatory. We use telluric OH lines and a helium arc lamp to characterize refractive effects through the filter and to confirm our understanding of the filter transmission profile. We benchmark our new technique by observing a transit of WASP-69b and detect an excess absorption of 0.498% ± 0.045% (11.1σ), consistent with previous measurements after considering our bandpass. We then use this method to study the inflated gas giant WASP-52b and place a 95th percentile upper limit on excess absorption in our helium bandpass of 0.47%. Using an atmospheric escape model, we constrain the mass-loss rate for WASP-69b to be ( ) at 7000 K (12,000 K). Additionally, we set an upper limit on the mass-loss rate of WASP-52b at these temperatures of ( ). These results show that ultranarrowband photometry can reliably quantify absorption in the metastable helium feature.

The HI/OH/Recombination line survey of the inner Milky Way (THOR): data release 2 and H I overview

Context.The Galactic plane has been observed extensively by a large number of Galactic plane surveys from infrared to radio wavelengths at an angular resolution below 40′′. However, a 21 cm line and continuum survey with comparable spatial resolution is lacking.Aims.The first half of THOR data (l= 14.0°−37.9°, andl= 47.1°−51.2°, |b|≤ 1.25°) has been published in our data release 1 paper. With this data release 2 paper, we publish all the remaining spectral line data and Stokes I continuum data with high angular resolution (10′′–40′′), including a new H Idataset for the whole THOR survey region (l= 14.0−67.4° and |b|≤ 1.25°). As we published the results of OH lines and continuum emission elsewhere, we concentrate on the H Ianalysis in this paper.Methods.With theKarl G. JanskyVery Large Array (VLA) in C-configuration, we observed a large portion of the first Galactic quadrant, achieving an angular resolution of ≤40′′. AtLBand, the WIDAR correlator at the VLA was set to cover the 21 cm H Iline, four OH transitions, a series of Hnαradio recombination lines (RRLs;n= 151 to 186), and eight 128 MHz-wide continuum spectral windows, simultaneously.Results.We publish all OH and RRL data from the C-configuration observations, and a new H Idataset combining VLA C+D+GBT (VLA D-configuration and GBT data are from the VLA Galactic Plane Survey) for the whole survey. The H Iemission shows clear filamentary substructures at negative velocities with low velocity crowding. The emission at positive velocities is more smeared-out, likely due to higher spatial and velocity crowding of structures at the positive velocities. Compared to the spiral arm model of the Milky Way, the atomic gas follows the Sagittarius and Perseus Arm well, but with significant material in the inter-arm regions. With the C-configuration-only H I+continuum data, we produce an H Ioptical depth map of the THOR areal coverage from 228 absorption spectra with the nearest-neighbor method. With thisτmap, we corrected the H Iemission for optical depth, and the derived column density is 38% higher than the column density with optically thin assumption. The total H Imass with optical depth correction in the survey region is 4.7 × 108 M⊙, 31% more than the mass derived assuming the emission is optically thin. If we applied this 31% correction to the whole Milky Way, the total atomic gas mass would be 9.4–10.5 × 109 M⊙. Comparing the H Iwith existing CO data, we find a significant increase in the atomic-to-molecular gas ratio from the spiral arms to the inter-arm regions.Conclusions.The high-sensitivity and resolution THOR H Idataset provides an important new window on the physical and kinematic properties of gas in the inner Galaxy. Although the optical depth we derive is a lower limit, our study shows that the optical depth correction issignificant for H Icolumn density and mass estimation. Together with the OH, RRL and continuum emission from the THOR survey, these new H Idata provide the basis for high-angular-resolution studies of the interstellar medium in different phases.

Evolution of the H2O Maser Emission in the Star-Forming Region S252A

Results of observations of the star-forming region S252A in the 1.35-cm H2O and 18-cm OH lines obtained using the 22-m Pushchino (Russia) and Nancay (France) radio telescopes are presented. A catalog of H2O maser spectra for 1995-2019 is presented. The variability of the integrated flux has two components: a cyclic component with a time interval between cycles ~30-35 yrs and a short-period component with a mean period of about 2.6 yrs. This may reflect non-stationary formation of a protostar. It is shown that the medium where the H2O maser emission and thermal OH emission are generated is strongly fragmented, and contains small-scale turbulent motions comparable to the thermal motions of the matter. The observed drift and jumps in the radial velocity of the H2O emission features could be a consequence of complex, non-uniform structure of the maser condensations.

Iron Contamination in High-Enthalpy Test Facilities: OH PLIF Imaging Considerations

Thermometry measurements were performed in a scramjet combustor using thermally-assisted laser-induced fluorescence. Experimental data were obtained through laser-induced fluorescence where a laser beam was focused into the combustor and the OH () transition at 283.55 nm was excited. Measurements in the 360 nm spectral region resulted in detection of a strong fluorescence line. Investigation of this phenomenon led to the conclusion that when the OH line is chosen for excitation, another line of a different species that lies very close to is also unintentionally excited. The second species has been identified as iron, Fe I. The assumption is that the erosion of the shock tunnel walls introduced iron in the flow that is excited with the laser when exciting OH. Thus, it is very important to ensure that this is avoided in future. Instead, another OH excitation line should be used for OH excitation line in planar laser-induced fluorescence (PLIF) experiments where iron may potentially also be present in the flow. Alternatively, fluorescence from this iron line can be circumvented by proper filtering of the PLIF. A proposal is made to turn the iron contamination into advantage by using iron present in the non-combusting flow for PLIF.

A Spectral Analysis of the Centimeter Regime of Nearby Galaxies: RRLs, Excited OH, and NH3

Centimeter-wave transitions are important counterparts to the rotational mm-wave transitions usually observed to study gas in star-forming regions. However, given their relative weakness, these transitions have historically been neglected. We present Australia Telescope Compact Array 4cm- and 15mm-band spectral line observations of nine nearby star-forming galaxies in the H75 array configuration. Thirteen different molecular lines are detected across the sample from OH, NH$_3$, H$_2$O, H$_2$CO, and c-C$_3$H$_2$, as well as 18 radio recombination lines (RRLs) in NGC 253. Excited OH $^2\Pi_{3/2}$ absorption is detected towards NGC 253 (J=5/2), NGC 4945 (J=9/2), and Circinus (J=9/2); the latter two represent only the third and fourth extragalactic J=9/2 detections. These lines in Circinus suggest rotation temperatures in excess of 2000 K, and thus it is likely that the populations of OH rotational states are not governed by a Boltzmann distribution. Circinus's OH lines are blueshifted from the systemic velocity by ~35 km s$^{-1}$, while NGC 4945's are redshifted by ~100 km s$^{-1}$. NGC 4945's OH absorption likely indicates infall onto the nucleus. The NH$_3$ (1,1) through (6,6) lines in NGC 4945 display a superposition of emission and absorption similar to that seen in other dense gas tracers. Strong (3,3) emission points towards maser activity. The relative NH$_3$ absorption strengths in NGC 4945 show similar anomalies as in previous studies of Arp 220 (weak (1,1) and strong (5,5) absorption). A trend towards higher LTE electron temperatures with increasing RRL frequency is present in NGC 253, likely indicative of stimulated emission within the nuclear region.

Detection of 4765 MHz OH Emission in a Preplanetary Nebula: CRL 618

Abstract Jets and outflows are ubiquitous phenomena in astrophysics, found in our Galaxy in diverse environments, from the formation of stars to late-type stellar objects. We present observations conducted with the 305 m Arecibo Telescope of the preplanetary nebula CRL 618 (Westbrook Nebula)—a well-studied late-type star that has developed bipolar jets. The observations resulted in the first detection of 4765 MHz OH in a late-type stellar object. The line was narrow (FWHM ∼ 0.6 km s−1) and ∼40 km s−1 blueshifted with respect to the systemic velocity, which suggests association with the expanding jets/bullets in CRL 618. We also report nondetection at Arecibo of any other OH transition between 1 and 9 GHz. The nondetections were obtained during the observations in 2008, when the 4765 MHz OH line was first discovered, and also in 2015 when the 4765 MHz OH line was not detected. Our data indicate that the 4765 MHz OH line was a variable maser. Modeling of the 4765 MHz OH detection and nondetection of the other transitions is consistent with the physical conditions expected in CRL 618. The 4765 MHz OH maser could originate from dissociation of H2O by shocks after sublimation of icy objects in this dying carbon-rich stellar system, although other alternatives such as OH in an oxygen-rich circumstellar region associated with a binary companion are also possible.

Effects of dust evolution on protoplanetary disks in the mid-infrared

In this paper, we couple the dust evolution code two-pop-py with the thermochemical disk modelling code ProDiMo. We create a series of thermochemical disk models that simulate the evolution of dust over time from 0.018 to 10 Myr, including the radial drift, growth, and settling of dust grains. We examine the effects of this dust evolution on mid-infrared gas emission, focusing on the mid-infrared spectral lines of C2H2, CO2, HCN, NH3, OH, and H2O, which are readily observable with Spitzer and the upcoming E-ELT and JWST. The addition of dust evolution acts to increase line fluxes by reducing the population of small dust grains. We find that the spectral lines of all species except C2H2 respond strongly to dust evolution; line fluxes increase by more than an order of magnitude across the model series as the density of small dust grains decreases over time. The C2H2 line fluxes are extremely low because of a low abundance in the infrared line-emitting regions, even though C2H2 is commonly detected with Spitzer, suggesting that warm chemistry in the inner disk may need further investigation. Finally, we find that the CO2 flux densities increase more rapidly than the other species as the dust disk evolves. This suggests that the flux ratios of CO2 to other species may be lower in disks with less-evolved dust populations.

Be and O in the ultra metal-poor dwarf 2MASS J18082002-5104378: the Be–O correlation

Context. Measurable amounts of Be could have been synthesised primordially if the Universe were non-homogeneous or in the presence of late decaying relic particles. Aims. We investigate the Be abundance in the extremely metal-poor star 2MASS J1808-5104 ([Fe/H] = −3.84) with the aim of constraining inhomogeneities or the presence of late decaying particles. Methods. High resolution, high signal-to-noise ratio (S/N) UV spectra were acquired at ESO with the Kueyen 8.2 m telescope and the UVES spectrograph. Abundances were derived using several model atmospheres and spectral synthesis code. Results. We measured log(Be/H) = −14.3 from a spectrum synthesis of the region of the Be line. Using a conservative approach, however we adopted an upper limit two times higher, i.e. log(Be/H) < −14.0. We measured the O abundance from UV–OH lines and find [O/H] = −3.46 after a 3D correction. Conclusions. Our observation reinforces the existing upper limit on primordial Be. There is no observational indication for a primordial production of 9Be. This places strong constraints on the properties of putative relic particles. This result also supports the hypothesis of a homogeneous Universe, at the time of nucleosynthesis. Surprisingly, our upper limit of the Be abundance is well below the Be measurements in stars of similar [O/H]. This may be evidence that the Be–O relation breaks down in the early Galaxy, perhaps due to the escape of spallation products from the gas clouds in which stars such as 2MASS J1808-5104 have formed.

Database of molecular masers and variable stars

We present the database of maser sources in H2O, OH and SiO lines that can be used to identify and study variable stars at evolved stages. Detecting the maser emission in H2O, OH and SiO molecules toward infrared-excess objects is one of the methods for identifing long-period variables (LPVs, including miras and semiregulars), because these stars exhibit maser activity in their circumstellar shells. Our sample contains 1803 known LPV objects. Forty-six percent of these stars (832 objects) manifest maser emission in the line of at least one molecule: H2O, OH or SiO. We use the database of circumstellar masers in order to search for LPVs which are not included in the General Catalogue of Variable Stars (GCVS). Our database contains 4806 objects (3866 objects without associations in GCVS) with maser detection in at least one molecule. Therefore it is possible to use the database in order to locate and study the large sample of LPV stars. The database can be accessed at http://maserdb.net.

Hidden or missing outflows in highly obscured galaxy nuclei?

Context. Understanding the nuclear growth and feedback processes in galaxies requires investigating their often obscured central regions. One way to do this is to use (sub)millimeter line emission from vibrationally excited HCN (HCN-vib), which is thought to trace warm and highly enshrouded galaxy nuclei. It has been suggested that the most intense HCN-vib emission from a galaxy is connected to a phase of nuclear growth that occurs before the nuclear feedback processes have been fully developed. Aims. We aim to investigate if there is a connection between the presence of strong HCN-vib emission and the development of feedback in (ultra)luminous infrared galaxies ((U)LIRGs). Methods. We collected literature and archival data to compare the luminosities of rotational lines of HCN-vib, normalized to the total infrared luminosity, to the median velocities of 119 μm OH absorption lines, potentially indicating outflows, in a total of 17 (U)LIRGs. Results. The most HCN-vib luminous systems all lack signatures of significant molecular outflows in the far-infrared OH absorption lines. However, at least some of the systems with bright HCN-vib emission have fast and collimated outflows that can be seen in spectral lines at longer wavelengths, including in millimeter emission lines of CO and HCN (in its vibrational ground state) and in radio absorption lines of OH. Conclusions. We conclude that the galaxy nuclei with the highest LHCN − vib/LIR do not drive wide-angle outflows that are detectable using the median velocities of far-infrared OH absorption lines. This is possibly because of an orientation effect in which sources oriented in such a way that their outflows are not along our line of sight also radiate a smaller proportion of their infrared luminosity in our direction. It could also be that massive wide-angle outflows destroy the deeply embedded regions responsible for bright HCN-vib emission, so that the two phenomena cannot coexist. This would strengthen the idea that vibrationally excited HCN traces a heavily obscured stage of evolution before nuclear feedback mechanisms are fully developed.

Water and OH Emission from the Inner Disk of a Herbig Ae/Be Star

Abstract We report the detection of hot H2O and OH emission from the Herbig Ae/Be star HD 101412 using the Cryogenic Infrared Echelle Spectrograph on the Very Large Telescope. Previous studies of Herbig Ae/Be stars have shown the presence of OH around some of these sources, but H2O has proven more elusive. While marginal water emission has been reported in the mid-infrared, and a few Herbig Ae/Be stars show water emission in the far-infrared, water emission near 2.9 μm has not been previously detected. We apply slab models to the rovibrational OH, H2O, and CO spectra of this source and show that the molecules are consistent with being cospatial. We discuss the possibility that the detection of the CO overtone bandhead emission, detection of water emission, and the large line to continuum contrast of the OH lines may be connected to its high inclination and the λ Boö nature of this star. If the low abundance of refractories results from the selective accretion of gas relative to dust, the inner disk of HD 101412 should be strongly dust-depleted, allowing us to probe deeper columns of molecular gas in the disk, enhancing its molecular emission. Our detection of C- and O-bearing molecules from the inner disk of HD 101412 is consistent with the expected presence, in this scenario, of abundant volatiles in the accreting gas.

The EDIBLES survey

We report cosmic ray ionization rates toward ten reddened stars studied within the framework of the EDIBLES (ESO Diffuse Interstellar Bands Large Exploration Survey) program, using the VLT-UVES. For each sightline, between two and ten individual rotational lines of OH+ have been detected in its (0,0) and (1,0) A3Π − X3Σ− electronic band system. This allows constraining of OH+ column densities toward different objects. Results are also presented for 28 additional sightlines for which only one or rather weak signals are found. An analysis of these data makes it possible to derive the primary cosmic ray ionization rate ζp in the targeted diffuse interstellar clouds. For the ten selected targets, we obtain a range of values for ζp equal to (3.9–16.4) × 10−16 s−1. These values are higher than the numbers derived in previous detections of interstellar OH+ in the far-infrared/submillimeter-wave regions and in other near-ultraviolet studies. This difference is a result of using new OH+ oscillator strength values and a more complete picture of all relevant OH+ formation and destruction routes (including the effect of proton recombinations on PAHs), and the relatively high N(OH+) seen toward those ten targets.

Gemini IFU, VLA, and HST observations of the OH Megamaser Galaxy IRAS17526 + 3253★

AbstractWe present a multiwavelength study of the OH megamaser galaxy IRAS17526 + 3253, based on new Gemini multi-object spectrograph integral field unit (GMOS/IFU) observations, Hubble Space Telescope F814W, and H α + [N ii] images, and archival 2MASS and 1.49 GHz VLA data. The Hubble Space Telescope(HST) images clearly reveal a mid-to-advanced stage major merger whose northwestern and southeastern nuclei have a projected separation of ∼8.5 kpc. Our HST/H α + [N ii] image shows regions of ongoing star formation across the envelope on ∼10 kpc scales, which are aligned with radio features, supporting the interpretation that the radio emission originates from star-forming regions. The measured H α luminosities imply that the unobscured star formation rate (SFR) is ∼10–30 M⊙ yr−1. The GMOS/IFU data reveal two structures in northwestern separated by 850 pc and by a discontinuity in the velocity field of ∼ 200 km s−1. We associate the blueshifted and redshifted components with, respectively, the distorted disc of northwestern and tidal debris, possibly a tail originating in southeastern. Star formation is the main ionization source in both components, which have SFRs of ∼2.6–7.9 M⊙ yr−1 and ∼1.5–4.5 M⊙ yr−1, respectively. Fainter line emission bordering these main components is consistent with shock ionization at a velocity ∼200 km s−1 and may be the result of an interaction between the tidal tail and the northwestern galaxy’s disc. IRAS17526 + 3253 is one of only a few systems known to host both luminous OH and H2O masers. The velocities of the OH and H2O maser lines suggest that they are associated with the northwestern and southeastern galaxies, respectively (Martin et al.; Wagner).

Investigation of turbulence flow characteristics in a dual-mode scramjet combustor using hydroxyl tagging velocimetry

The results of an investigation of the turbulence characteristics of a kerosene-fueled, dual-mode scramjet combustor are reported in this paper. The combustor had a cavity flame holder and was operated at an inlet Mach number of 2. The combustor was made to transition across different modes by adjusting the fuel injection and inlet flow total temperature. The velocity and fluctuations thereof in the flow field upstream of the combustion zone were measured using the hydroxyl tagging velocimetry method. Given a signal-to-noise ratio of about 4 for the OH lines and considering the effect of dithering of the optical equipment owing to strong vibration, the uncertainty in the measured velocity was about 29 m/s. The computational fluid dynamics solution of the flow was compared with the measurements, and the computed positions of the shock wave trains were used to distinguish the combustion modes. The results show that the turbulence fluctuation velocity (u'rms) in the supersonic mode was the same as that in the case of the nonreacting flow, but it was considerably higher in the subsonic mode. During the ram-to-scram process, the turbulence intensity (u'rms/ū) declined exponentially as the local Mach number of the flow field upstream of the combustion zone increased.

Technical characteristics of a DC plasma jet with Ar/N2 and O2/N2 gaseous mixtures

In this paper, the optical emission spectroscopy technique is used to examine the physical properties and technical characteristics of the plasma discharge in a fabricated DC plasma jet. The background gas is nitrogen molecular gas which is mixed with argon and oxygen gases at various percentages. The emission spectra are analyzed and, the plasma density, rotational, vibrational and excitation temperatures are obtained for the formed plasma discharges with Ar/N2 and O2/N2 mixtures. Moreover, the NO and OH lines from NOγ(A2Σ+→X2Πr), (A2Σ,v=0→X2Π,v′=0) excitation transitions are observed. It is shown that, at the higher argon and oxygen percentages in both the Ar/N2 and O2/N2 gaseous mixture, the emission intensities of argon ions and oxygen atoms are increased. In addition, at the higher Ar and O2 contributions in both the gaseous mixtures, while the rotational, vibrational and excitation temperatures are higher, they are decreased at the O2/N2 gaseous mixture. Moreover, the plasma electron density reduces for O2/N2 and increases for Ar/N2 gaseous mixture. On the other hand, for both the mixtures, the plasma density, rotational, vibrational and excitation temperatures are increased at the higher DC power source currents. Furthermore, it is seen that the N2 dissociation rate increases at the higher DC currents and Ar and O2 percentages in both the mixtures. However, N2 dissociation rate in the formed plasma jet with Ar/N2 gaseous mixture is higher.

An Updated Line List for NUV Spectral Synthesis in Evolved Stars: Redetermination of the Beryllium Abundance in the Solar Photosphere

Abstract Motivated by the desire to measure beryllium abundances in red giant stars, we have constructed a new line list for synthesizing spectra in the near-ultraviolet. Using the Sun, Arcturus, and Pollux as benchmark stars, we explore potential sources of missing continuous opacity and line absorption. Despite the inclusion of new sources of continuous opacity, fitting the ultraviolet OH lines in the solar spectrum still requires artificially inflating the continuous opacity. The red giants also require the addition of a line of unknown origin in the blue wing of the Be line at λ3131.065 Å, and we find a good match can be made by adopting a Ti ii line with low excitation potential. The inclusion of this line does not affect the measurement of the solar Be abundance. Because the fits to all of the benchmark stars require tuning the properties of known spectral lines and including both an unknown source of additional continuous opacity and spectral lines of unknown origin, we argue that the absolute abundances of Be in stars should be interpreted with caution. Therefore, the question of whether the solar Be abundance is depleted may not yet be resolved, although our model favors minimal Be depletion in the Sun.