Search

Start Over Subject atomic physics Publisher CDS Validation Level 2
1. 3600-24700{AA} deep X-shooter spectrum of HH 1
ID:
ivo://CDS.VizieR/J/ApJ/814/52
Title:
3600-24700{AA} deep X-shooter spectrum of HH 1
Short Name:
J/ApJ/814/52
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present deep spectroscopic (3600-24700{AA}) X-shooter observations of the bright Herbig-Haro object HH 1, one of the best laboratories to study the chemical and physical modifications caused by protostellar shocks on the natal cloud. We observe atomic fine structure lines, HI and HeI recombination lines and H_2_ ro-vibrational lines (more than 500 detections in total). Line emission was analyzed by means of Non-local Thermal Equilibiurm codes to derive the electron temperature and density, and for the first time we are able to accurately probe different physical regimes behind a dissociative shock. We find a temperature stratification in the range 4000K/80000K, and a significant correlation between temperature and ionization energy. Two density regimes are identified for the ionized gas, a more tenuous, spatially broad component (density ~10^3^/cm^3^), and a more compact component (density>=10^5^/cm^3^) likely associated with the hottest gas. A further neutral component is also evidenced, having a temperature <~10000K and a density >10^4^/cm^3^. The gas fractional ionization was estimated by solving the ionization equilibrium equations of atoms detected in different ionization stages. We find that neutral and fully ionized regions co-exist inside the shock. Also, indications in favor of at least partially dissociative shock as the main mechanism for molecular excitation are derived. Chemical abundances are estimated for the majority of the detected species. On average, abundances of non-refractory/refractory elements are lower than solar of about 0.15/0.5dex. This indicates the presence of dust inside the medium, with a depletion factor of iron of ~40%.
2. Absolute photoionization cross sections
ID:
ivo://CDS.VizieR/J/A+A/439/387
Title:
Absolute photoionization cross sections
Short Name:
J/A+A/439/387
Date:
21 Oct 2021
Publisher:
CDS
Description:
Absolute photoionization cross sections for the ions N2+, N3+, O3+, O4+, F3+ , F4+ and Ne4+ are measured using the merged-beam technique, combining the synchrotron radiation from an undulator at the storage ring ASTRID with ions produced by an ECR ion source. The files contain the experimental absolute cross-section data reported in the paper. Each ascii file has 3 columns: Photon energy (eV), Cross section (Mb) and Statistical uncertainty (Mb). In addition to the latter there is a systematic uncertainty on the cross sections of about 15%. (1Mb=10^-18^cm^2^).
3. Absorption coefficient of polystyrene
ID:
ivo://CDS.VizieR/J/A+A/517/A60
Title:
Absorption coefficient of polystyrene
Short Name:
J/A+A/517/A60
Date:
21 Oct 2021
Publisher:
CDS
Description:
The surfaces of airless bodies in the Solar System are continuously altered by the bombardment of micrometeoroids and irradiation by solar wind, flares, and cosmic particles. Major effects of this process - space weathering - are darkening and "reddening" of the spectra of surface materials, as well as a "degrading" of absorption features. We studied the changes induced by energetic ion irradiation in the ultraviolet-visual-near-infrared (UV-Vis-NIR) (0.2-0.98um) reflectance spectra of targets selected to mimic the surfaces of airless bodies in the inner Solar System. Our chosen targets are olivine pellets, pure or covered by an organic polymer (polystyrene), which is transparent before irradiation. Polystyrene is used as a template for organic matter of low volatility that can be present on asteroidal surfaces. Moreover we measured the changes induced by ion irradiation in the absorption coefficient of the polymer. The purpose was to have a tool to better compare laboratory with observed spectra and distinguish between planetary objects with pure silicate surfaces and those whose surface is covered by organic matter exposed to cosmic ion bombardment.
4. Absorption spectrum of SO up to 2.5THz
ID:
ivo://CDS.VizieR/J/ApJ/799/115
Title:
Absorption spectrum of SO up to 2.5THz
Short Name:
J/ApJ/799/115
Date:
21 Oct 2021
Publisher:
CDS
Description:
In order to obtain accurate terahertz center frequencies for SO and its isotopologues, we have studied the absorption spectrum of SO, ^34^SO, and ^33^SO up to 2.5THz using continuous-wave terahertz photomixing based on a frequency comb providing an accuracy down to 10kHz. Sulfur monoxide was produced in a radio frequency discharge of air in a cell containing pure sulfur. Together with the strong absorption signal of the main isotopologue, transitions of ^34^SO (^34^S: 4.21%) and ^33^SO (^33^S: 0.75%) were observed in natural abundance. The newly observed transitions constitute an extension of the observed rotational quantum numbers of the molecule toward higher N values, allowing an improvement of the molecular parameters for the three species. An isotopically invariant fit has been performed based on pure rotational and ro-vibrational transitions of all SO isotopologues, enabling their accurate line position prediction at higher frequencies. Thanks to this new set of parameters, it is now possible to predict with very high accuracy the frequencies of the ro-vibrational lines. This should enable the research of SO in the mid-IR using ground-based IR telescopes, space-based telescope archives (Infrared Space Observatory, Spitzer), and future space missions such as the James Webb Space Telescope. This set of parameters is particularly well adapted for the detection of SO lines in O-rich evolved stars or in molecular clouds in absorption against bright IR sources.
5. Abundances in PNe. III: Se and Kr
ID:
ivo://CDS.VizieR/J/ApJS/218/25
Title:
Abundances in PNe. III: Se and Kr
Short Name:
J/ApJS/218/25
Date:
21 Oct 2021
Publisher:
CDS
Description:
The detection of neutron(n)-capture elements in several planetary nebulae (PNe) has provided a new means of investigating s-process nucleosynthesis in low-mass stars. However, a lack of atomic data has inhibited accurate trans-iron element abundance determinations in astrophysical nebulae. Recently, photoionization (PI) and recombination data were determined for Se and Kr, the two most widely detected n-capture elements in nebular spectra. We have incorporated these new data into the photoionization code Cloudy (Ferland et al. 2013RMxAA..49..137F). To test the atomic data, numerical models were computed for 15 PNe that exhibit emission lines from multiple Kr ions. We found systematic discrepancies between the predicted and observed emission lines that are most likely caused by inaccurate PI and recombination data. These discrepancies were removed by adjusting the Kr^+^-Kr^3+^ PI cross sections within their cited uncertainties and the dielectronic recombination rate coefficients by slightly larger amounts. From grids of models spanning the physical conditions encountered in PNe, we derive new, broadly applicable ionization correction factor (ICF) formulae for calculating Se and Kr elemental abundances. The ICFs were applied to our previous survey of near-infrared [KrIII] and [SeIV] emission lines in 120 PNe. The revised Se and Kr abundances are 0.1-0.3dex lower than former estimates, with average values of [Se/(O,Ar)]=0.12+/-0.27 and [Kr/(O,Ar)]=0.82+/-0.29, but correlations previously found between their abundances and other nebular and stellar properties are unaffected. We also find a tendency for high-velocity PNe that can be associated with the Galactic thick disk to exhibit larger s-process enrichments than low-velocity PNe belonging to the thin-disk population.
6. Abundances of 26 barium stars. II.
ID:
ivo://CDS.VizieR/J/A+A/454/917
Title:
Abundances of 26 barium stars. II.
Short Name:
J/A+A/454/917
Date:
21 Oct 2021
Publisher:
CDS
Description:
The aim of this work is to quantify the contributions of the s-, r-, and p-processes for the total abundance of heavy elements from abundances derived for a sample of 26 barium stars. The abundances of the sample stars were compared to those of normal stars, thus identifying the fraction relative to the main component of the s-process s. The fittings of the sigmaN curves (neutron-capture cross-section times abundance, plotted against atomic mass number) for the sample stars suggest that the material from the companion asymptotic giant branch star had approximately the solar isotopic composition as concerns fractions of abundances relative to the s-process main component.
7. Acetaldehyde CH_2_DCOH and CH_3_COD
ID:
ivo://CDS.VizieR/J/A+A/624/A70
Title:
Acetaldehyde CH_2_DCOH and CH_3_COD
Short Name:
J/A+A/624/A70
Date:
21 Oct 2021
Publisher:
CDS
Description:
Detection of deuterated species may provide information on the evolving chemistry in the earliest phases of star-forming regions. For molecules with two isomeric forms of the same isotopic variant, gas-phase and solid-state formation pathways can be differentiated using their abundance ratio. Spectroscopic databases for astrophysical purposes are built for the two mono deuterated isomeric species CH_2_DCOH and CH_3_COD of the complex organic molecule acetaldehyde. These databases can be used to search and detect these two species in astrophysical surveys, retrieving their column density and therefore abundances. Submillimeter wave and terahertz transitions were measured for mono deuterated acetaldehyde CH2DCOH which is a non-rigid species displaying internal rotation of its asymmetrical CH_2_D methyl group. An analysis of a dataset consisting of previously measured microwave data and the newly measured transition was carried out with a model accounting for the large amplitude torsion. The frequencies of 2556 transitions are reproduced with a unitless standard deviation of 2.3 yielding various spectroscopic constants. Spectroscopic databases for astrophysical purposes were built for CH_2_DCOH using the results of the present analysis and for CH_3_COD using the results of a previous spectroscopic investigation. These two species were both searched for and are detected toward a low-mass star-forming region. We report the first detection of CH2DCOH (93 transitions) and the detection of CH_3_COD (43 transitions) species in source B of the IRAS 16293-2422 young stellar binary system located in the {rho} Ophiuchus cloud region, using the publicly available ALMA Protostellar Interferometric Line Survey.
8. Al I & Al II absolute transition probabilities
ID:
ivo://CDS.VizieR/J/A+A/388/704
Title:
Al I & Al II absolute transition probabilities
Short Name:
J/A+A/388/704
Date:
21 Oct 2021
Publisher:
CDS
Description:
Relative intensity measurements of Al I and Al II spectral lines in the visible and ultraviolet spectral ranges are performed using a capacitively coupled high frequency double hollow electrode discharge. Branching ratios and intensity ratios within multiplets are determined. By using selected lifetimes absolute transition probabilities are calculated.
9. AlI and AlII extended transition rates
ID:
ivo://CDS.VizieR/J/A+A/621/A16
Title:
AlI and AlII extended transition rates
Short Name:
J/A+A/621/A16
Date:
21 Oct 2021
Publisher:
CDS
Description:
MultiConfiguration Dirac-Hartree-Fock (MCDHF) and relativistic configuration interaction (RCI) calculations were performed for 28 and 78 states in neutral and singly ionized aluminium, respectively. In AlI the configurations of interest are 3s^2^nl for n=3,4,5 with l=0 to 4, as well as 3s3p^2^ and 3s^2^6l for l=0,1,2. In AlII, in addition to the ground configuration 3s^2^, the studied configurations are 3snl with n=3 to 6 and l=0 to 5, 3p^2^, 3s7s, 3s7p, and 3p3d. Valence and core-valence electron correlation effects are systematically accounted for through large configuration state function (CSF) expansions. Calculated excitation energies are found to be in excellent agreement with experimental data from the National Institute of Standards and Technology (NIST) database. Lifetimes and transition data for radiative electric dipole (E1) transitions are given and compared with results from previous calculations and available measurements for both AlI and AlII. The computed lifetimes of AlI are in very good agreement with the measured lifetimes in high-precision laser spectroscopy experiments. The present calculations provide a substantial amount of updated atomic data, including transition data in the infrared region. This is particularly important since the new generation of telescopes are designed for this region. There is a significant improvement in accuracy, in particular for the more complex system of neutral AlI. The complete tables of transition data are available online.
10. ALMA obs. of star-forming regions toward NGC6334I
ID:
ivo://CDS.VizieR/J/ApJ/883/129
Title:
ALMA obs. of star-forming regions toward NGC6334I
Short Name:
J/ApJ/883/129
Date:
21 Oct 2021
Publisher:
CDS
Description:
The relative column densities of the structural isomers methyl formate, glycolaldehyde, and acetic acid are derived for a dozen positions toward the massive star-forming regions MM1 and MM2 in the NGC 6334I complex, which are separated by ~4000au. Relative column densities of these molecules are also gathered from the literature for 13 other star-forming regions. In this combined data set, a clear bimodal distribution is observed in the relative column densities of glycolaldehyde and methyl formate. No such distribution is evident with acetic acid. The two trends are comprised of star-forming regions with a variety of masses, suggesting that there must be some other common parameter that is heavily impacting the formation of glycolaldehyde. This is indicative of some demonstrable differentiation in these cores; studying the abundances of these isomers may provide a clue as to the integral chemical processes ongoing in a variety of protostellar environments.

Limit your search