- ID:
- ivo://CDS.VizieR/J/A+A/591/A75
- Title:
- Millimeter wave spectrum of methyl cyanate
- Short Name:
- J/A+A/591/A75
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The recent discovery of methyl isocyanate (CH_3_NCO) in Sgr B2(N) and Orion KL makes methyl cyanate (CH_3_OCN) a potential molecule in the interstellar medium. The aim of this work is to fulfill the first requirement for its unequivocal identification in space, i.e. the availability of transition frequencies with high accuracy. The room-temperature rotational spectrum of methyl cyanate was recorded in the millimeter wave domain from 130 to 350GHz. All rotational transitions revealed A-E splitting owing to methyl internal rotation and were globally analyzed using the ERHAM program. The data set for the ground torsional state of methyl cyanate exceeds 700 transitions within J"=10-35 and K"a=0-13 and newly derived spectroscopic constants reproduce the spectrum close to the experimental uncertainty. Spectral features of methyl cyanate were then searched for in Orion KL, Sgr B2(N), B1-b, and TMC-1 molecular clouds. Upper limits to the column density of methyl cyanate are provided.
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- ID:
- ivo://CDS.VizieR/J/A+A/577/A91
- Title:
- Millimeter wave spectrum of vinyl acetate
- Short Name:
- J/A+A/577/A91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The recent discovery of methyl acetate in Orion KL makes vinyl acetate, CH3-(C=O)-O-CH=CH2, a potential molecule in the interstellar medium.We obtained very accurate spectroscopic constants in a comprehensive laboratory analysis of its rotational spectra which can be used to predict those transition frequencies towards interstellar sources. We present the experimental study and theoretical analysis of the ground torsional state of vinyl acetate in a large spectral range for astrophysical use. The room-temperature rotational spectrum of vinyl acetate has been measured from 125 to 305GHz to provide direct frequencies to the astronomical community. Additional measurements have also been made using a broadband CP-FTMWspectrometer in the region of 6 - 18 GHz. Transition lines, corresponding to the most stable conformer, have been observed and assigned. All the rotational transitions revealed the A-E splitting due to the methyl internal rotation and had to be treated with a specific internal rotation code (BELGI-Cs). We analyzed 2508 transitions up to J"=75 for vt=0 for the most stable conformer of vinyl acetate. The new lines were globally fitted with previously published data and 24 parameters of the Hamiltonian were accurately determined. The spectral features of vinyl acetate were then searched for in Orion KL. Using the whole line survey of Orion KL (80-280GHz) obtained with the IRAM 30m radio telescope we can provide only an upper limit to the column density of vinyl acetate. However, using the ALMA Science Verification data we obtain a tentative detection of this species that will require further search at other frequencies to confirm its presence in this high mass star forming region.
- ID:
- ivo://CDS.VizieR/J/A+A/549/A38
- Title:
- Millimetre and infrared spectrum of DC_4_H
- Short Name:
- J/A+A/549/A38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Diacetylene, C_4_H_2_, has been identified in several astronomical environments through its infrared spectrum. In contrast, monodeuterated diacetylene (DC_4_H) has not been detected in space so far owing to the low isotopic abundance of deuterated species but also to the rather poor laboratory spectroscopic characterisation of this molecule. The aim of this work is to provide accurate spectroscopic parameters for DC_4_H to achieve reliable predictions for both its spectra at millimetre and infrared wavelengths. We studied the rotational spectrum of DC_4_H in the range 85-615GHz by millimetre-wave spectroscopy and the infrared spectrum below 1000cm-1 by high-resolution, Fourier-transform spectroscopy. Several pure rotational transitions were recorded in the ground state and in excited vibrational bending states. The three fundamental bands v6, v7, and v8 have been identified and assigned in the infrared spectrum.
- ID:
- ivo://CDS.VizieR/J/ApJS/166/650
- Title:
- mm/sbmm spectrum of iso-propanol
- Short Name:
- J/ApJS/166/650
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Iso-propanol [(CH_3_)_2_CHOH], an isomer of n-propanol, has been studied in the millimeter- and submillimeter-wave region of the electromagnetic spectrum with our FASSST spectrometer through 360GHz. Spectra arising from the ground vibrational state of all three hydroxyl torsional substates, given the labels symmetric gauche, antisymmetric gauche, and trans in order of increasing energy, have been observed. We have successfully assigned ~7600 pure rotational transitions within the torsional substates as well as ~4700 torsional-rotational transitions between the symmetric and antisymmetric gauche substates through the lower rotational quantum number J"=68. Spectral lines involving one or both of the two gauche forms have been simultaneously analyzed with a 2x2 effective torsional-rotational Hamiltonian, which includes terms through fifth order in the torsional-rotational interaction. Excluding perturbed transitions, the assigned transitions were fitted to a root mean square deviation of 76kHz. The trans substate was analyzed as a semirigid rotor, and its unperturbed transitions fitted to a root mean square deviation of 63kHz. A perturbation was seen at transitions with J">50 in the trans substate. The torsional excitation energy for the trans substate above ground was estimated from intensity ratios to be about 120K.
- ID:
- ivo://CDS.VizieR/J/ApJS/216/2
- Title:
- MnI hyperfine lines in the 1.4-1.8um (H) band
- Short Name:
- J/ApJS/216/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The three Mn I lines at 17325, 17339, and 17349{AA} are among the 25 strongest lines (log(gf)>0.5) in the H band. They are all heavily broadened due to hyperfine structure, and the profiles of these lines have so far not been understood. Earlier studies of these lines even suggested that they were blended. In this work, the profiles of these three infrared (IR) lines have been studied theoretically and compared to experimental spectra to assist in the complete understanding of the solar spectrum in the IR. It is shown that the structure of these lines cannot be described in the conventional way using the diagonal A and B hyperfine interaction constants. The off-diagonal hyperfine interaction not only has a large impact on the energies of the hyperfine levels, but also introduces a large intensity redistribution among the hyperfine lines, changing the line profiles dramatically. By performing large-scale calculations of the diagonal and off-diagonal hyperfine interaction and the gf-values between the upper and lower hyperfine levels and using a semi-empirical fitting procedure, we achieved agreement between our synthetic and experimental spectra. Furthermore, we compare our results with observations of stellar spectra. The spectra of the Sun and the K1.5 III red giant star Arcturus were modeled in the relevant region, 1.73-1.74{mu}m, using our theoretically predicted gf-values and energies for each individual hyperfine line. Satisfactory fits were obtained and clear improvements were found using our new data compared with the old available Mn I data.
- ID:
- ivo://CDS.VizieR/J/A+AS/125/539
- Title:
- Mn III transition probabilities
- Short Name:
- J/A+AS/125/539
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Transition probabilities of the spectrum of Mn III are calculated using the orthogonal operator description for both the odd and the even energy levels.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A80
- Title:
- Mn lines 3D NLTE formation in late-type stars
- Short Name:
- J/A+A/631/A80
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Manganese (Mn) is a key Fe-group element, commonly employed in stellar population and nucleosynthesis studies to explore the role of SN Ia.We have developed a new non-local thermodynamic equilibrium (NLTE) model of Mn, including new photo-ionisation cross-sections and new transition rates caused by collisions with H and H- atoms. We applied the model in combination with onedimensional (1D) LTE model atmospheres and 3D hydrodynamical simulations of stellar convection to quantify the impact of NLTE and convection on the line formation. We show that the effects of NLTE are present in MnI and, to a lesser degree, in MnII lines, and these increase with metallicity and with the effective temperature of a model. Employing 3D NLTE radiative transfer, we derive a new abundance of Mn in the Sun, A(Mn)=5.52+/-0.03dex, consistent with the element abundance in CI meteorites. We also applied our methods to the analysis of three metal-poor benchmark stars. We find that 3D NLTE abundances are significantly higher than 1D LTE. For dwarfs, the differences between 1D NLTE and 3D NLTE abundances are typically within 0.15 dex, however, the effects are much larger in the atmospheres of giants owing to their more vigorous convection. We show that 3D NLTE successfully solves the ionisation and excitation balance for the RGB star HD 122563 that cannot be achieved by 1D LTE or 1D NLTE modelling. For HD 84937 and HD 140283, the ionisation balance is satisfied, however, the resonance MnI triplet lines still show somewhat lower abundances compared to the high-excitation lines. Our results for the benchmark stars confirm that 1D LTE modelling leads to significant systematic biases in Mn abundances across the full wavelength range from the blue to the IR. We also produce a list of Mn lines that are not significantly biased by 3D and can be reliably, within the 0.1 dex uncertainty, modelled in 1D NLTE.
- ID:
- ivo://CDS.VizieR/J/MNRAS/421/2786
- Title:
- Modelling of shock waves molecular line emission
- Short Name:
- J/MNRAS/421/2786
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have developed further the technique of time-dependent modelling of magnetohydrodynamic shock waves, with a view to interpreting the molecular line emission from outflow sources. The extensively observed source L1157 B1 was chosen as an exemplar of the application of this technique.
- ID:
- ivo://CDS.VizieR/J/ApJ/519/697
- Title:
- Molecular study of HC_3_NH^+^+e^-^
- Short Name:
- J/ApJ/519/697
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The dissociative recombination reaction between HC_3_NH^+^ and electrons is an important process in the chemistry of interstellar clouds. Motivated by the evidence that HCN and its metastable isomer HNC are both formed via the dissociative recombination reaction of HCNH^+^, we have examined the potential energy surface for the dissociation of the transient HC_3_NH following the recombination between HC_3_NH^+^ and electrons. We find that HC_3_NH^+^ gains 151 kcal mol^-1^ energy by the neutralization; this energy is high enough to isomerize HC_3_NH to HCCNCH, as well as to dissociate a hydrogen atom from either end of the molecule. The present calculation suggests, therefore, that the metastable linear and near-linear isomers of HC_3_N, namely, HNC_3_, HCCNC, and HCNCC, can be formed via the dissociative recombination between HC_3_NH^+^ and electrons. Two of these isomers, HNC3 and HCCNC, have already been detected in the dark cloud TMC-1. The unobserved species HCNCC is energetically the least stable. Since interstellar HC_3_N molecules are synthesized predominantly via neutral-neutral reactions, the HC_3_NH^+^ + e^-^ process serves mainly to produce the metastable isomers of HC_3_N.
- ID:
- ivo://CDS.VizieR/J/A+A/579/A46
- Title:
- Mono-^13^C acetaldehydes mm/submm wave spectra
- Short Name:
- J/A+A/579/A46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The acetaldehyde molecule is ubiquitous in the interstellar medium of our galaxy, and due to its dense and complex spectrum, large dipole moment, and several low-lying torsional states, acetaldehyde is considered to be a "weed" molecule for radio astronomy observations. Mono-^13^C acetaldehydes ^13^CH_3_CHO and CH_3_^13^CHO are likely to be identified in astronomical surveys, such as those available with the very sensitive ALMA telescope. Laboratory measurements and analysis of the millimeter and submillimeter-wave spectra are the prerequisites for the successful radioastronomical search for the new interstellar molecular species, as well as for new isotopologs of already detected interstellar molecules. In this context, to provide reliable predictions of ^13^CH_3_CHO and CH_3_^13^CHO spectra in millimeter and submillimeter wave ranges, we study rotational spectra of these species in the frequency range from 50 to 945GHz. The spectra of mono-^13^C acetaldehydes were recorded using the spectrometer based on Schottky-diode frequency-multiplication chains in the Lille laboratory. The rotational spectra of ^13^CH_3_CHO and CH_3_^13^CHO molecules were analyzed using the Rho axis method.
