High-resolution Emission Spectra Research Articles

Comparative Planetology of Magnetic Effects in Ultrahot Jupiters: Trends in High-resolution Spectroscopy

Ultrahot Jupiters (UHJs), being the hottest class of exoplanets known, provide a unique laboratory for testing atmospheric interactions with internal planetary magnetic fields at a large range of temperatures. Thermal ionization of atmospheric species on the dayside of these planets results in charged particles becoming embedded in the planet’s mostly neutral wind. The charges will resist flow across magnetic field lines as they are dragged around the planet and ultimately alter the circulation pattern of the atmosphere. We model this process to study this effect on high-resolution emission and transmission spectra in order to identify observational signatures of the magnetic circulation regime that exist across multiple UHJs. Using a state-of-the-art kinematic MHD/active drag approach in a 3D atmospheric model, we simulate three different UHJs with and without magnetic effects. We postprocess these models to generate high-resolution emission and transmission spectra and explore trends in the net Doppler shift as a function of phase. In emission spectra, we find that the net Doppler shift before and after secondary eclipse can be influenced by the presence of magnetic drag and the wavelength choice. Trends in transmission spectra show our active drag models consistently produce a unique shape in their Doppler shift trends that differs from the models without active drag. This work is a critical theoretical step to understanding how magnetic fields shape the atmospheres of UHJs and provides some of the first predictions in high-resolution spectroscopy for observing these effects.

Visible Opacities of S-type Stars: The d 3Φ–a 3Δ Band System of ZrO

ZrO is a well-studied metal monoxide because of its astrophysical importance in characterizing S stars. The bands of the d 3Φ–a3Δ system (γ system) with v′≤4 and v″ ≤ 5 are rotationally analyzed using the PGOPHER program to provide spectroscopic constants. The high-resolution ZrO emission spectrum was recorded with a Fourier transform spectrometer using a high-temperature carbon furnace source. New ab initio calculations of the transition dipole moment were carried out in order to determine the vibronic band strengths. The spectroscopic constants, along with the band strengths, are used to calculate a line list for the γ system. This line list can be used to determine Zr abundances in S stars. We also correct the line strengths for the B 1Π–A 1Δ transition calculated in our previous work.

A high-resolution spectroscopic technique for the analysis of the external quantum efficiency of a multimode semiconductor laser

The high-resolution emission spectra of a GaN-based semiconductor laser were utilized to investigate the external differential quantum efficiency variation with temperature and stability over an extended period of continuous operation time. Moreover, the dynamics and evolution of the optical gain and longitudinal modes emitted both below and above threshold current were also reported. Upon studying the L-I curves over the full range of operating current and temperature, three distinct temperature regimes of the quantum efficiency were identified, with the regime of the temperature range 285–301 K yielding the highest stability. The thermal stability of the laser was also assessed by monitoring the variation of threshold current with temperature.

ESPRESSO reveals blueshifted neutral iron emission lines on the dayside of WASP-76 b

Context. Ultra hot Jupiters (gas giants with Teq > 2000 K) are intriguing exoplanets due to the extreme physics and chemistry present in their atmospheres. Their torrid daysides can be characterised using ground-based high-resolution emission spectroscopy. Aims. We search for signatures of neutral and singly ionised iron (Fe I and Fe II, respectively) in the dayside of the ultra hot Jupiter WASP-76 b, as these species were detected via transmission spectroscopy in this exoplanet. Furthermore, we aim to confirm the existence of a thermal inversion layer, which has been reported in previous studies, and attempt to constrain its properties. Methods. We observed WASP-76 b on four epochs with ESPRESSO at the VLT, at orbital phases shortly before and after the secondary transit, when the dayside is in view. We present the first analysis of high-resolution optical emission spectra for this exoplanet. We compare the data to synthetic templates created with petitRADTRANS, using cross-correlation function techniques. Results. We detect a blueshifted (−4.7 ± 0.3 km s−1) Fe I emission signature on the dayside of WASP-76 b at 6.0σ. The signal is detected independently both before and after the eclipse, and it is blueshifted in both cases. The presence of iron emission features confirms the existence of a thermal inversion layer. Fe II was not detected, possibly because this species is located in the upper layers of the atmosphere, which are more optically thin. Thus the Fe II signature on the dayside of WASP-76 b is too weak to be detected with emission spectroscopy. Conclusions. We propose that the blueshifted Fe I signature is created by material rising from the hot spot to the upper layers of the atmosphere, and discuss possible scenarios related to the position of the hotspot. This work unveils some of the dynamic processes ongoing on the dayside of the ultra hot Jupiter WASP-76 b through the analysis of the Fe I signature from its atmosphere, and complements previous knowledge obtained from transmission studies. It also highlights the ability of ESPRESSO to probe the dayside of this class of exoplanets.

Molecules in Cool Stars: The A2Π − X2Σ+ and the B2Σ+ − X2Σ+ Band Systems of CaCl

Cool red giant stars exhibit absorption bands of calcium monochloride (CaCl) in the optical region. In this work, the bands of CaCl corresponding to the A2Π − X2Σ+ transition with v′≤ 4 and v″ ≤ 4, and B2Σ+ − X2Σ+ transition with v′≤ 2 and v″ ≤ 2 are rotationally analyzed with PGOPHER, a multipurpose program for simulating and fitting molecular spectra. All bands were analyzed using high-resolution absorption spectra collected at the National Solar Observatory in 1985, calibrated with atomic lines from a high-resolution emission spectrum obtained in a separate hollow cathode experiment. The results are compared with previous laser-induced fluorescence measurements. Overall, the accuracy of spectroscopic constants for the A2Π and B2Σ+ states is improved. Scaled transition dipole moment calculations were used to obtain line strengths. Line lists are provided with Einstein A coefficients and oscillator strengths, which can be used to determine CaCl stellar abundances. Additionally, isotope splittings allowed us to estimate band origins for the 40Ca37Cl isotopologue based on band-head positions.

Influence of O-H⋅⋅⋅Pt interactions on photoluminescent response in the (Et4N)2{[Pt(bph)(CN)2][phenylene-1,4-diresorcinol]} framework.

Tunable photoluminescence (PL) is one of the hot topics in current materials science, and research performed on the molecular phases is at the forefront of this field. We present the new (Et4N)2[PtII(bph)(CN)2]⋅rez3⋅1/3H2O (Pt2rez3) (bph=biphenyl-2,2'-diyl; rez3=3,3",5,5"-tetrahydroxy-1,1':4',1"-terphenyl, phenylene-1,4-diresorcinol coformer, a linear quaternary hydrogen bond donor) co-crystal salt based on the recently appointed promising [PtII(bph)(CN)2]2- luminophore. Within the extended hydrogen-bonded subnetwork [PtII(bph)(CN)2]2- complexes and rez3 coformer molecules form two types of contacts: the rez3O-H⋅⋅⋅Ncomplex ones in the equatorial plane of the complex and non-typical rez3O-H⋅⋅⋅Pt ones along its axial direction. The combined structural, PL, and DFT approach identified the rez3O-H⋅⋅⋅Pt synthons to be crucial in promoting the noticeable uniform redshift of bph ligand centered (LC) emission compared to the LC emission of the (Et4N)2[PtII(bph)(CN)2]⋅H2O (Pt2) precursor, owing to the direct interference of the phenol group with the PtII-bph orbital system via altering the CT processes within. The high-resolution emission spectra for Pt2 and Pt2rez3 were successfully reproduced at 77 K by using the Franck-Cordon expressions. The possibility to tune PL properties along the plausible continuum of rez3O-H⋅⋅⋅Pt synthons is indicated, considering various scenarios of molecular occupation of the space above and below the complex plane.

Contrasting impact of coordination polyhedra and site symmetry on the electronic energy levels in nine-coordinated Eu(III) and Sm(III) crystals structures determined from single crystal luminescence spectra.

Lanthanide luminescence is characterised by "forbidden" 4f-4f transitions and a complicated electronic structure. Our understanding of trivalent lanthanide(III) ion luminescence is centered on Eu3+ because absorbing and emitting transitions in Eu3+ occur from a single electronic energy level. In Sm3+ both absorbing and emitting multiplets have a larger multiplicity. A band arising in transitions from the first emitting state multiplet to the ground state multiplet will have nine lines for a Sm3+ complex. In this study, high-resolution emission and excitation spectra were used to determine the electronic energy levels for the lowest multiplet and first emitting multiplet in four Sm3+ compounds with either tricapped trigonal prismatic TTP or capped square antiprismatic cSAP coordination polyhedra but different site symmetry. This was achieved by the use of Boltzmann distribution population analysis and experimentally determined transition probabilities from emission and excitation spectra. Using this analysis it was possible to show the effect of changing three oxygen atoms with three nitrogen atoms in the donor set for two compounds with the same coordination polyhedra and site symmetry. This work celebrates the 40th anniversary of Kirby and Richardson's first report of [Eu(ODA)3]3- luminescence.

Atmospheric Metallicity and C/O of HD 189733 b from High-resolution Spectroscopy

We present high-resolution K-band emission spectra of the quintessential hot Jupiter HD 189733 b from the Keck Planet Imager and Characterizer. Using a Bayesian retrieval framework, we fit the dayside pressure–temperature profile, orbital kinematics, mass-mixing ratios of H2O, CO, CH4, NH3, HCN, and H2S, and the 13CO/12CO ratio. We measure mass fractions of and , and place upper limits on the remaining species. Notably, we find logCH4 < −4.5 at 99% confidence, despite its anticipated presence at the equilibrium temperature of HD 189733 b assuming local thermal equilibrium. We make a tentative (∼3σ) detection of 13CO, and the retrieved posteriors suggest a 12C/13C ratio similar to or substantially less than the local interstellar value. The possible 13C enrichment would be consistent with accretion of fractionated material in ices or in the protoplanetary disk midplane. The retrieved abundances correspond to a substantially substellar atmospheric C/O = 0.3 ± 0.1, while the carbon and oxygen abundances are stellar to slightly superstellar, consistent with core-accretion models which predict an inverse correlation between C/O and metallicity. The specific combination of low C/O and high metallicity suggests significant accretion of solid material may have occurred late in the formation process of HD 189733 b.

Opacities of S-type Stars: The Singlet B 1Π–X 1Σ+, B 1Π–A 1△, and C 1Σ+–X 1Σ+ Band Systems of ZrO

The ZrO B 1Π–X 1Σ+, B 1Π–A 1Δ, and C 1Σ+–X 1Σ+ band systems are important opacity sources in the near-infrared and optical spectra of S-type stars. A total of 21 rovibronic bands with v″ ≤ 7 and were observed and fit for the B 1Π–X 1Σ+ transition, five bands for the 90ZrO B 1Π–A 1Δ transition and one band for the 90ZrO C 1Σ+–X 1Σ+ transition. All band systems were analyzed using high-temperature, high-resolution emission spectra collected at the National Solar Observatory (Kitt Peak). A modern spectroscopic analysis was performed using the PGOPHER program to provide updated spectroscopic constants. In general, we improve the accuracy of the line positions reported in the literature and slightly extend the vibrational analysis. Equilibrium molecular constants were then derived and combined with new ab initio calculations of transition dipole moment functions to produce line lists with line strengths.

ExoMol line lists – LIV. Empirical line lists for AlH and AlD and experimental emission spectroscopy of AlD in A1Π (v = 0, 1, 2)

ABSTRACT New ExoMol line lists AloHa for aluminium hydride (AlH and AlD) are presented improving the previous line lists WYLLoT. The revision is motivated by the recent experimental measurements and astrophysical findings involving the highly excited rotational states of AlH in its A 1Π − X 1Σ+ system. A new high-resolution emission spectrum of 10 bands from the A 1Π − X 1Σ+ system of AlD, in the region 17 300–32 000 cm−1 was recorded with a Fourier transform spectrometer, which probes the predissociative A 1Π v = 2 state. The AlD new line positions are combined with all available experimental data on AlH and AlD to construct a comprehensive set of empirical rovibronic energies of AlH and AlD covering the X 1Σ+ and A 1Π electronic states using the MARVEL approach. We then refine the spectroscopic model WYLLoT to our experimentally derived energies using the nuclear-motion code Duo and use this fit to produce improved line lists for 27AlH, 27AlD, and 26AlH with a better coverage of the rotationally excited states of A 1Π in the predissociative energy region. The lifetimes of the predissociative states are estimated and are included in the line list using the new ExoMol data structure, alongside the temperature-dependent continuum contribution to the photoabsorption spectra of AlH. The new line lists are shown to reproduce the experimental spectra of both AlH and AlD well, and to describe the AlH absorption in the recently reported Proxima Cen spectrum, including the strong predissociative line broadening. The line lists are included into the ExoMol data base www.exomol.com.

Stellar surface information from the Ca ii H&amp;K lines – I. Intensity profiles of the solar activity components

ABSTRACT The detection of Earth-like planets with the radial-velocity (RV) method is currently limited by the presence of stellar activity signatures. On rotational time-scales, spots and plages (or faculae) are known to introduce different RV signals, but their corrections require better activity proxies. The best-known chromospheric activity proxies in the visible are the Ca ii H&amp;K lines, but the physical quantities measured by their profiles need to be clarified. We first investigate resolved images of the Sun in order to better understand the spectrum of plages, spots, and the network using the Meudon spectroheliogram. We show that distinct line profiles are produced by plages, spots, and by the network component and we also derived the centre-to-limb variations of the three profiles. Some care is required to disentangle their contributions due to their similarities. By combining disc-integrated spectra from the ISS high-resolution spectrograph with SDO direct images of the Sun, we managed to extract a high-resolution emission spectrum of the different components, which tend to confirm the spectra extracted from the Meudon spectroheliogram datacubes. Similar results were obtained with the HARPS-N Sun-as-a-star spectra. We concluded using a three-component model that the temporal variation of the popular Sindex contains, on average for the 24th solar cycle: $70\pm 12{{\ \rm per\ cent}}$ of plage, $26\pm 12{{\ \rm per\ cent}}$ of network, and $4\pm 4 {{\ \rm per\ cent}}$ of spots. This preliminary investigation suggests that a detailed study of the Ca ii H&amp;K profiles may provide rich information about the filling factor and distribution of different types of active regions.

Slow magnetic relaxation and photoluminescence behaviors of dilanthanide complexes bearing N8O2 donor macrocyclic ligand

On account of the complicated magnetic exchange interactions between lanthanide ions, binuclear lanthanide complexes have broad application prospect in the field of single-molecule magnets. Therefore, it is necessary to develop reasonable bridging ligands to manipulate the directional assembly of binuclear lanthanide complexes. Herein, we selected the macrocyclic ligand LN8O2 to build up two new dilanthanide complexes [Ln2(LN8O2) (OpyO)2(H2O)2](NO3)2 (1-Ln, Ln = Dy, Tb; LN8O2 = hexamethyl-tetraaza-dioxe-dipyrazolacycloicosaphane-2,9,12,19-tetraene; OpyOH = 2-pyridinol-1-oxide). Dynamic magnetic studies show that 1-Dy exhibits slow relaxation behavior under a 1 kOe applied field. Further fitting analysis of relaxation times gives the effective energy barrier of 38.2 cm−1, and reveals that the slow magnetic relaxation behavior is dominated by the Orbach and Raman processes. High-resolution luminescence emission spectrum indicates the energy gap of 36.8 cm−1 between the ground state and the first excited state, consistent with the magnetic measurement results. 1-Tb exhibits brilliant characteristic green light emission under UV light excitation. The absolute quantum yield of 1-Tb is 44.8%, and its first-order fitted decay lifetime is 779.21 μs at room temperature. This study provides the way for directional construction of high-performance molecular materials with magnetic and optical dual-function.

Mid-infrared laser heterodyne spectrometer byhollow optical fiber and its newly designedcoupler.

We demonstrate a newly designed, to the best of our knowledge, hollow optical fiber coupler for a mid-infrared (IR) laser heterodyne spectrometer that mixes a targeted light source with local oscillator (LO) light. The hollow fiber achieves a high transmission efficiency ∼80-90%/m, not only for a coherent laser source but also for an incoherent blackbody source. The branching characteristics of the hollow optical fiber coupler are found to be strongly dependent on the curvature and length of the input port fiber, indicating that the branching ratio could be designed independently for each input port. Our laboratory measurements demonstrate that the branching ratio and transmittance of the coupler can be varied by coupling a flexible fiber to the input side owing to the excitation of higher-order modes. Using the hollow optical fiber coupler, a high-resolution emission spectrum of the quantum cascade laser at 10.3µm for our C O 2 laser-based heterodyne spectrometer is successfully achieved. Using a C O 2 laser with a hollow fiber and a blackbody as a direct input signal in free space, we obtain the sensitivity performance of IR laser heterodyne spectrometer as 2000-3000K of the system noise temperature. This suggests that the transmission of a coherent LO laser through a hollow optical fiber has almost the same sensitivity for the IR heterodyne detection as that without a fiber.

Retrieval of atmospheric trace gases from satellite infrared limb sounding data

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument which operated in the near-to-mid infrared on the Envisat satellite from 2002–2012 is a Fourier-transform spectrometer for the measurement of high-resolution atmospheric emission spectra at the Earth’s limb. The initial operational products are profiles of temperature, H2O, O3, CH4, N2O, HNO3, and NO2, and this list is extended to include the important GHG (greenhouse gases) and ODS (ozone depleting substances) species using MORSE (orbital retrieval processor). This paper discusses retrievals of minor trace species of HCFC-22, HOCl, OCS, C2H6, COF2, HCN, CF4, SF6, and CCl4. Preliminary zonal mean results of these retrievals are satisfactory except for HCN and CF4 species. We then use MIPAS to estimate the total F and Cl budget in the atmosphere. Comparisons with SLIMCAT are also discussed, with the results consistent. Finally, we focus on improving the retrieval method for minor trace species, COF2, by adjusting correlation length and a priori constraint, as well as the chi-square method introduced to analyze noise. Tests have shown that our improvement could get more information from the measurements.

High-resolution FT-VIS emission spectroscopy of the [formula omitted] system of AlH

An extensive high-resolution visible wavelength emission spectrum of AlH, that covers eight bands of the A1Π−X1Σ+ system, has been observed with a Fourier-transform spectrometer for the first time. The 0−0,1,2 and 1−0,1,2,3,4 bands were recorded with an instrumental resolution of 0.03 cm−1. The best signal-to-noise ratio of 9000:1 was obtained for the strongest 0−0 band. In total, 259 ro-vibronic frequencies were measured with an absolute accuracy of about 0.0020 cm−1. The experimental data were fitted using the PGOPHER program written by Western (2017). Molecular constants were derived for the X1Σ+, ν=0−4 and A1Π, ν=0,1 levels. Also derived were rotational term values for the A1Π, ν=0,1 levels. The current data were combined with the previous ground state results of White et al. (1993) using the instruction called the constraints on parameters within PGOPHER. The Dunham parameters (Ykl) for the A1Π state of AlH were determined for the first time. A very small shifts of the A1Π, ν=0,J=17 and ν=1,J=5 levels have been observed and identified as result of the possible interaction between A1Π and 3Σ+ states.

Magnetic Drag and 3D Effects in Theoretical High-resolution Emission Spectra of Ultrahot Jupiters: the Case of WASP-76b

Ultrahot Jupiters are ideal candidates to explore with high-resolution emission spectra. Detailed theoretical studies are necessary to investigate the range of spectra that we can expect to see from these objects throughout their orbit, because of the extreme temperature and chemical longitudinal gradients that exist across their dayside and nightside regions. Using previously published 3D general circulation models of WASP-76b with different treatments of magnetic drag, we postprocess the 3D atmospheres to generate high-resolution emission spectra for two wavelength ranges, throughout the planet’s orbit. We find that the high-resolution emission spectra vary strongly as a function of phase, at times showing emission features, absorption features, or both, which are a direct result of the 3D structure of the planet. At phases exhibiting both emission and absorption features, the Doppler shift differs in direction between the two spectral features, making them differentiable, instead of canceling each other out. Through the use of cross correlation, we find different patterns in net Doppler shift for models with different treatments of drag: the nightside spectra show opposite signs in their Doppler shift, while the dayside phases display a reversal in the trend of net shift with phase. Finally, we caution researchers against using a single spectral template throughout the planet’s orbit; this can bias the corresponding net Doppler shift returned, as it can pick up on a bright region on the edge of the planet disk that is highly redshifted or blueshifted.

High-resolution spectral models of TRAPPIST-1e seen as a Pale Blue Dot for ELT and JWST observations

ABSTRACT Rocky exoplanets orbiting in the habitable zone (HZ) of nearby M dwarfs provide unique opportunities for characterizing their atmospheres and searching for biosignature gases. TRAPPIST-1e, a temperate Earth-sized exoplanet in the HZ of a nearby M dwarf, is arguably the most favourable target for ground- and space-based atmospheric characterization by the extremely large telescopes (ELTs) and the James Webb Space Telescope. To inform future observations in reflected and emitted lights using these upcoming telescopes, we simulate the high-resolution reflection and emission spectra for TRAPPIST-1e for both modern and prebiotic Earth-like atmospheric compositions. To demonstrate the effects of wavelength-dependent albedo on climate and spectra, we further simulate five albedo scenarios for each atmospheric composition: cloudy modern Earth-like, cloud-free modern Earth-like, cloudy ocean planet, 100 per cent cloudy planet, and wavelength-independent albedo of 0.31. We use the recent Mega-MUSCLES spectral energy distribution of TRAPPIST-1 for our models. We show that the O2 + CH4 and O3 + CH4 biosignature pairs as well as climate indicators (CO2 and H2O) show features in both high-resolution reflection and emission spectra of TRAPPIST-1e that the ELTs can search for. Our high-resolution data base for modern and prebiotic Earth TRAPPIST-1e models with various surface compositions and cloud distributions provides a tool for observers to train retrieval algorithms and plan observation strategies to characterize this potentially habitable world.

Probing luminescence of rare earth ions in natural pink fluorites using Raman microscopes

AbstractIt is well‐known that many natural fluorite crystals contain rare earth ions. In this work, a series of pink fluorites is studied to demonstrate that the use of Raman microscopes allows to obtain high resolution emission spectra of trivalent rare earth ions. These emission spectra allow in principle to distinguish differences of the local environment related to the charge compensation necessary when the divalent Ca ion is replaced by a trivalent rare earth ion. The pink fluorites from the Alps have grown under hydrothermal conditions, which results in the incorporation of oxygen into the fluorite. In one sample from Juchlistock (Bern, Switzerland), a trigonal Eu3+‐oxygen center is clearly identified. Interestingly, a pink fluorite from China (Huanggang Mine, Inner Mongolia, China) shows a quite different emission spectrum from those of the Alps. In this sample, the emission bands have much lower relative intensity compared with the intensity of the CaF2 Raman peak, indicating a much lower content of Er3+ and Ho3+ which emit around 520–560 nm. Literature examples show that Raman measurements of differently colored fluorite crystals can also present sharp rare earth spectra. By extension, it is thus possible to observe and identify emission spectra of rare earth ions in other mineral crystals using Raman microspectroscopy and avoid misassignments of the corresponding observed Raman spectra.

Modeling the High-resolution Emission Spectra of Clear and Cloudy Nontransiting Hot Jupiters

Abstract The advent of high-resolution spectroscopy (R ≳ 25,000) as a method for characterization of exoplanet atmospheres has expanded our capability to study nontransiting planets, vastly increasing the number of planets accessible for observation. Many of the most favorable targets for atmospheric characterization are hot Jupiters, where we expect large spatial variation in physical conditions such as temperature, wind speed, and cloud coverage, making viewing geometry important. Three-dimensional models have generally simulated observational properties of hot Jupiters assuming edge-on viewing, which can be compared to observations of transiting planets, but neglected the large fraction of planets without nearly edge-on orbits. As the first investigation of how orbital inclination manifests in high-resolution emission spectra from three-dimensional models, we use a general circulation model to simulate the atmospheric structure of Upsilon Andromedae b, a typical nontransiting hot Jupiter with high observational interest, due the brightness of its host star. We compare models with and without clouds, and find that cloud coverage intensifies spatial variations by making colder regions dimmer and relatedly enhancing emission from the clear, hotter regions. This increases both the net Doppler shifts and the variation of the continuum flux amplitude over the course of the planet’s orbit. In order to accurately capture scattering from clouds, we implement a generalized two-stream radiative transfer routine for inhomogeneous multiple scattering atmospheres. As orbital inclination decreases, four key features of the high-resolution emission spectra also decrease in both the clear and cloudy models: (1) the average continuum flux level, (2) the amplitude of the variation in continuum with orbital phase, (3) net Doppler shifts of spectral lines, and (4) Doppler broadening in the spectra. Models capable of treating inhomogeneous cloud coverage and different viewing geometries are critical in understanding results from high-resolution emission spectra, enabling an additional avenue to investigate these extreme atmospheres.

Near-infrared and Visible Opacities of S-type Stars: The B1Π—X1Σ+ Band System of ZrO

Abstract The ZrO B1Π—X1Σ+ transition is an important opacity source in the near-infrared and optical spectrum of S-type stars. The 0–0, 0–1, 0–2, 1–0, 1–2, 1–3, 2–0, 2–1, 2–3, 2–4, 3–1, 3–4, and 4–2 bands of the 90Zr16O B1Π—X1Σ+ transition are reanalyzed using a high-temperature (2390 K) high-resolution (0.04 cm−1) emission spectrum collected at the National Solar Observatory (Kitt Peak). A modern spectroscopic analysis was performed using the PGOPHER program to provide updated spectroscopic constants and to produce a high-precision line list with line strengths based on an ab initio calculation of the transition dipole moment.