Knowledge of the elemental abundances of symbiotic giants is essential to address the role of chemical composition in the evolution of symbiotic binaries, to map their parent population, and to trace their mass transfer history. However, there are few symbiotic giants for which the photospheric abundances are fairly well determined. This is the second in a series of papers on chemical composition of symbiotic giants determined from high-resolution (R~50000) near-IR spectra. Results are presented for the late-type giant star in the AE Ara, BX Mon, KX TrA, and CL Sco systems. Spectrum synthesis employing standard local thermal equilibrium (LTE) analysis and stellar atmosphere models were used to obtain photospheric abundances of CNO and elements around the iron peak (Sc, Ti, Fe, and Ni). Our analysis resulted in sub-solar metallicities in BX Mon, KX TrA, and CL Sco by [Fe/H]~-0.3 or -0.5 depending on the value of microturbulence. AE Ara shows metallicity closer to solar by ~0.2 dex. The enrichment in ^14^N isotope found in all these objects indicates that the giants have experienced the first dredge-up. In the case of BX Mon first dredge-up is also confirmed by the low ^12^C/^13^C isotopic ratio of ~8.
Linelists with calculated line positions and line intensities for ammonia (NH_3_) molecule and its three deuterated variants NH_2_D, ND_2_H, and ND_3_ with quadrupole coupling hyperfine splittings. Lines in linelists are formatted as in the JPL data base (Pickett, Poynter, Cohen et al. 1998, J. Quant. Spectrosc. Radiat. Transfer, 60, 883).
Pety et al. have reported the detection of eight transitions of a closed-shell, linear molecule (B11244) in observations toward the Horsehead photodissociation region (PDR), which they attribute to the l-C_3_H^+^ cation. Recent high-level ab initio calculations have called this assignment into question; the anionic C_3_H^-^ molecule has been suggested as a more likely candidate. Here, we examine observations of the Horsehead PDR, Sgr B2(N), TMC-1, and IRC+10216 in the context of both l-C_3_H^+^ and C_3_H^-^. We find no observational evidence of K_a_=1 lines, which should be present were the carrier indeed C_3_H^-^. Additionally, we find a strong anticorrelation between the presence of known molecular anions and B11244 in these regions. Finally, we discuss the formation and destruction chemistry of C_3_H^-^ in the context of the physical conditions in the regions. Based on these results, we conclude there is little evidence to support the claim that the carrier is C_3_H^-^.
New red and violet system line lists for the CN isotopologues ^13^C^14^N and ^12^C^15^N have been generated. These new transition data are combined with those previously derived for ^12^C^14^N, and applied to the determination of CNO abundances in the solar photosphere and in four red giant stars: Arcturus, the bright, very low-metallicity star HD 122563, and the carbon-enhanced metal-poor stars HD 196944 and HD 201626. When both red and violet system lines are detectable in a star, their derived N abundances are in good agreement. The mean N abundances determined in this work are also generally in accord with published values.
Vibration-rotation line lists for AlF, Al^35^Cl, and Al^37^Cl have been prepared in their ground electronic states (X^1^{Sigma}^+^). Experimental rotational and ro-vibrational lines were employed to calculate a potential energy surface (PES) by direct potential fitting. The PES was used to calculate ro-vibrational energy levels. Born-Oppenheimer Breakdown corrections were included in the energy level calculations for AlCl. Ro-vibrational energy levels were calculated for the v=0 to v=11 vibrational levels and up to Jmax=200 for the rotational levels. Dipole moment functions covering the range of the PES turning points were calculated for AlCl and AlF by ab initio methods and used to determine line intensities. Partition functions for temperatures up to 3000K were calculated. AlF and AlCl have been detected in circumstellar envelopes and are predicted to occur in cool stellar and sub- stellar atmospheres.
Vibration-rotation line lists for ^6^LiF, ^7^LiF, ^6^Li^35^Cl, ^6^Li^37^Cl, ^7^Li^35^Cl, and ^7^Li^37^Cl in the X^1^{Sigma}^+^ ground states have been prepared. The rovibrational energy levels have been calculated using potential energy surfaces determined by direct potential-fitting employing the rotational and rovibrational transition frequencies of all isotopologues, and required the inclusion of Born-Oppenheimer breakdown terms. Dipole moment functions calculated ab initio at the MRCI/aug-cc-pwCV5Z level have been used for line strength calculations. Partition functions for temperatures up to 5000K have been calculated. LiF and LiCl are predicted to be present in the atmospheres of hot rocky exoplanets, brown dwarfs, and cool stars.
A discharge of nitrogen gas, as created in a microwave-induced plasma, exhibits a very dense molecular emission line spectrum. Emission spectra of this kind could serve as wavelength calibrators for high-resolution astrophysical spectrographs in the near-infrared, where only very few calibration sources are currently available. The compilation of a spectral line list and the characterization of line intensities and line density belong to the initial steps when investigating the feasibility of potential wavelength calibration sources. Although the molecular nitrogen spectrum was extensively studied in the past, to our knowledge, no line list exists that covers a continuous range of several thousand wavenumbers in the near-infrared. We recorded three high-resolution spectra of a nitrogen gas discharge operated at different microwave powers. The nitrogen gas is kept inside a sealed glass cell at a pressure of 2mbar. The emission lines in the spectra were fitted by a superposition of Gaussian profiles to determine their position, relative intensity, and width. The line parameters were corrected for an absolute wavelength scale, instrumental line broadening, and intensity modulation. Molecular and atomic transitions of nitrogen were identified with available line positions from the literature. We report line lists with more than 40000 emission lines in the spectral range 4500-11000cm^-1^ (0.9-2.2{mu}m). The spectra exhibit emission lines over the complete spectral range under investigation with about 350-1300 lines per 100cm^-1^. Depending on the microwave power, a fraction of 35%-55% of all lines are blended. The total dynamic range of the detected lines covers about four orders of magnitude. Line density and peak intensities qualify the recorded discharge as a useful wavelength calibrator, and the line list provides an empirical reference for nitrogen spectra in the near-infrared.
In this paper, we present the results of an observational search for gas phase urea [(NH_2_)_2_CO] observed toward the Sgr B2(N-LMH) region. We show data covering urea transitions from ~100GHz to 250GHz from five different observational facilities: the Berkeley-Illinois-Maryland-Association (BIMA) Array, the Combined Array for Research in Millimeter-wave Astronomy (CARMA), the NRAO 12m telescope, the IRAM 30m telescope, and the Swedish-ESO Submillimeter Telescope (SEST). The results show that the features ascribed to urea can be reproduced across the entire observed bandwidth and all facilities by best-fit column density, temperature, and source size parameters which vary by less than a factor of two between observations merely by adjusting for telescope-specific parameters. Interferometric observations show that the emission arising from these transitions is cospatial and compact, consistent with the derived source sizes and emission from a single species. Despite this evidence, the spectral complexity of both (NH_2_)_2_ CO and of Sgr B2(N) makes the definitive identification of this molecule challenging. We present observational spectra, laboratory data, and models, and discuss our results in the context of a possible molecular detection of urea.
A consistent set of spectroscopic constants for the a^1^{Delta}, d^1^{Sigma}^+^, b^1^{Pi}, c^1^{Phi}, and f^1^{Delta} states of ^48^Ti^16^O has been determined from analysis of the b^1^{Pi}-a^1^{Delta}, b^1^{Pi}-d^1^{Sigma}^+^, c^1^{Phi}-a^1^{Delta}, and f^1^{Delta}-a^1^{Delta} systems. Three Fourier transform emission spectra have been used for the analysis. New bands of the b^1^{Pi}-a^1^{Delta} and c^1^{Phi}-a^1^{Delta} systems have been fitted. The first analysis of the c^1^{Phi}-a^1^{Delta} system using Fourier transform spectra is also provided. Extensive and improved line positions are measured. TiO is prominent in the spectra of oxygen-rich cool stellar objects and may be present in hot-Jupiter exoplanet atmospheres.
We present new unified theory line profiles of neutral Na perturbed by H_2_ . We used a priori NaH_2_ potentials, transition dipole moments and validated pseudo-potentials as input to the line shape, and evaluated the profiles for temperatures and densities appropriate for modeling exoplanet and brown dwarf atmospheres. The theory for the resonance lines was compared with new laboratory spectra of sodium to test the validity of the potentials and resulting profiles. The Lorentzian function commonly used to approximate a collisional line profile in radiative transfer calculations is shown to be inadequate, except within a few halfwidths of the line center. In the far wing, the opacity caused by collisions may be several orders of magnitude greater than the extrapolation of the Lorentzian core.
