- ID:
- ivo://CDS.VizieR/J/A+A/645/A64
- Title:
- Potential omega Cen associate EW
- Short Name:
- J/A+A/645/A64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Globular clusters (GCs) are important donors to the build-up of the Milky Way (MW) stellar halo, having contributed at the ten percent level over the Galactic history. Stars that originated from the second generation of dissolved or dissolving clusters can be readily identified via distinct light-element signatures such as enhanced N and Na and simultaneously depleted C and O abundances. In this paper we present an extensive chemical abundance analysis of the halo star J110842, which was previously kinematically associated with the massive MW GC {omega} Centauri ({omega} Cen), and we discuss viable scenarios from escape to encounter. Based on a high-resolution, high signal-to-noise spectrum of this star using the UVES spectrograph, we were able to measure 33 species of 31 elements across all nucleosynthetic channels. The star's low metallicity of [FeII/H]=2.10+/-0.02(stat.)+/-0.07(sys.) dex places it in the lower sixth percentile of {omega} Cen's metallicity distribution. We find that all of the heavier-element abundances, from - and Fepeak elements to neutron-capture elements are closely compatible with {omega} Cen's broad abundance distribution. However, given the major overlap of this object's abundances with the bulk of all of the MW components, this does not allow for a clear-cut distinction of the star's origin. In contrast, our measurements of an enhancement in CN and its position on the Na-strong locus of the Na-O anticorrelation render it conceivable that it originally formed as a second-generation GC star, lending support to a former association of this halo star with the massive GC {omega} Cen.
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- ID:
- ivo://CDS.VizieR/J/ApJ/726/25
- Title:
- Production of the p-process nuclei in SNe Ia
- Short Name:
- J/ApJ/726/25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We calculate the nucleosynthesis of proton-rich isotopes in the carbon-deflagration model for Type Ia supernovae (SNe Ia). The seed abundances are obtained by calculating the s-process nucleosynthesis that is expected to occur in the repeating helium shell flashes on the carbon-oxygen (CO) white dwarf (WD) during mass accretion from a binary companion. When the deflagration wave passes through the outer layer of the CO WD, p-nuclei are produced by photodisintegration reactions on s-nuclei in a region where the peak temperature ranges from 1.9 to 3.6x10^9^K. We confirm the sensitivity of the p-process on the initial distribution of s-nuclei. We show that the initial C/O ratio in the WD does not affect much the yield of p-nuclei. On the other hand, the abundance of ^22^Ne left after s-processing has a large influence on the p-process via the ^22^Ne({alpha},n) reaction. We find that about 50% of p-nuclides are co-produced when normalized to their solar abundances in all adopted cases of seed distribution. Mo and Ru, which are largely underproduced in Type II supernovae (SNe II), are produced more than in SNe II although they are underproduced with respect to the yield levels of other p-nuclides. The ratios between p-nuclei and iron in the ejecta are larger than the solar ratios by a factor of 1.2. We also compare the yields of oxygen, iron, and p-nuclides in SNe Ia and SNe II and suggest that SNe Ia could make a larger contribution than SNe II to the solar system content of p-nuclei.
- ID:
- ivo://CDS.VizieR/J/A+A/640/A98
- Title:
- Propargylimine in laboratory and in space
- Short Name:
- J/A+A/640/A98
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Small imines containing up to three carbon atoms are present in the interstellar medium. As alkynyl compounds are abundant in this medium, propargylimine (2-propyn-1-imine, HC=C-CH=NH) thus represents a promising candidate for a new interstellar detection. The goal of the present work is to perform a comprehensive laboratory investigation of the rotational spectrum of propargylimine in its ground vibrational state in order to obtain a highly precise set of rest-frequencies and to search it in space. The rotational spectra of E and Z geometrical isomers of propargylimine have been recorded in laboratory in the 83-500GHz frequency interval. The measurements have been performed using a source-modulation millimetre-wave spectrometer equipped with a pyrolysis system for the production of unstable species. High-level ab initio calculations were performed to assist the analysis and to obtain reliable estimates for an extended set of spectroscopic quantities. We have searched for propargylimine at 3 and 2mm in the spectral survey of the quiescent giant molecular cloud G+0.693-0.027 located in the "Central Molecular Zone", close to the Galactic Centre. About 1000 rotational transitions have been recorded for the E- and Z-propargylimine, in the laboratory. These new data have enabled the determination of a very accurate set of spectroscopic parameters including rotational, quartic and sextic centrifugal distortion constants. The improved spectral data allow us to perform a successful search for this new imine in the G+0.693-0.027 molecular cloud. Eighteen lines of Z-propargylimine have been detected at level >2.5*sigma, resulting in a column density estimate of N=(0.24+/-0.02)x10^-14^cm^-2^. An upper limit was retrieved for the higher-energy E isomer, which was not detected in the data. The fractional abundance (w.r.t. H_2_) derived for Z-propargylimine is 1.8x10^-10^. We discuss the possible formation routes by comparing the derived abundance with those measured in the source for possible chemical precursors.
- ID:
- ivo://CDS.VizieR/J/ApJS/218/30
- Title:
- Propenal (CH_2_CHCHO) transition frequencies
- Short Name:
- J/ApJS/218/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Since interstellar detection of propenal is only based on two rotational transitions in the centimeter wave region, its high resolution rotational spectrum has been measured up to 660GHz and fully characterized by assignment of more than 12000 transitions to provide direct laboratory data to the astronomical community. Spectral assignments and analysis include transitions from the ground state of the trans and cis isomers, three trans-^13^C isotopologues, and ten excited vibrational states of the trans form. Combining new millimeter and submillimeter data with those from the far-infrared region has yielded the most precise set of spectroscopic constants of trans-propenal obtained to date. Newly determined rotational constants, centrifugal distortion constants, vibrational energies, and Coriolis and Fermi interaction constants are given with high accuracy and were used to predict transition frequencies and intensities over a wide frequency range. Results of this work should facilitate astronomers further observation of propenal in the interstellar medium.
- ID:
- ivo://CDS.VizieR/J/ApJ/896/24
- Title:
- Properties of atomic lines in 51 Oph UV spectra
- Short Name:
- J/ApJ/896/24
- Date:
- 07 Mar 2022 13:24:57
- Publisher:
- CDS
- Description:
- We measured 304 absorption features in the ultraviolet and visible spectra of the star 51 Oph, which is known to have a debris disk with a high inclination. We analyzed the relative populations of atoms in excited fine-structure and metastable levels that are maintained by optical pumping and collisional excitation by electrons, and we found that most of the gas is situated at about 6 au from the star, has an electron volume density 10^5^<n(e)<3x10^6^cm^-3^, and a temperature T=8000K. Our interpretations reveal that the gas is partly ionized, has a column density of neutral hydrogen equal to 10^21^cm^-2^, and has a composition similar to that of a mildly depleted interstellar medium or that of Jupiter-family comets. Compared to results for disks around some other stars, such as {beta} Pic and 49 Cet, we find surprisingly little neutral carbon. No molecular features were detected, which indicates that our line of sight misses the molecule-rich central plane of the disk. The tilt of the disk is also validated by our being able to detect resonant scattering of the starlight by oxygen atoms.
- ID:
- ivo://CDS.VizieR/J/ApJ/788/119
- Title:
- Properties of the highly ionized gas of quasars
- Short Name:
- J/ApJ/788/119
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results from our NASA Keck Observatory Database of Ionized Absorbers toward Quasars (KODIAQ) survey which aims to characterize the properties of the highly ionized gas of galaxies and their circumgalactic medium (CGM) at 2<z<4. We select absorbers optically thick at the Lyman limit ({tau}_LL_>1, logN_HI_>17.3}) as probes of these galaxies and their CGM where both transitions of the O VI doublet have little contamination from the Ly{alpha}, {beta} forests. We found 20 absorbers that satisfy these rules: 7 Lyman limit systems (LLSs), 8 super-LLSs (SLLSs) and 5 damped Ly{alpha} (DLAs). The O VI detection rate is 100% for the DLAs, 71% for the LLSs, and 63% for the SLLSs. When O VI is detected, log(N_O VI_)=14.9+/-0.3, an average O VI column density substantially larger and with a smaller dispersion than found in blind O VI surveys at similar redshifts. Strong O VI absorption is therefore nearly ubiquitous in the CGM of z~2-3 galaxies. The total velocity widths of the O VI profiles are also large (200<={Delta}_{upsilon}_O VI_<=400 km/s). These properties are quite similar to those seen for O VI in low-z star-forming galaxies, and therefore we hypothesize that these strong CGM O VI absorbers (with {tau}_LL_>1) at 2<z<~3.5 also probe outflows of star-forming galaxies. The LLSs and SLLSs with no O VI absorption have properties consistent with those seen in cosmological simulations tracing cold streams feeding galaxies. When the highly ionized (Si IV and O VI) gas is taken into account, we determine that the {tau}_LL_>1 absorbers could contain as much as 3%-14% of the cosmic baryon budget at z~2-3, only second to the Ly{alpha} forest. We conservatively show that 5%-20% of the metals ever produced at z~2-3 are in form of highly ionized metals ejected in the CGM of galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJ/708/1452
- Title:
- Quadratic F_ij_ force field in l-CH_4_^-^
- Short Name:
- J/ApJ/708/1452
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using state-of-the-art theoretical methods, we investigate the stable isomers of C^-^_4_, C_4_H and C_4_H^-^. Three of them are relevant for astrophysics and astrochemistry. These computations are performed using highly correlated ab initio methods and the aug-cc-pVXZ (X=T,Q) basis sets. In addition to the linear isomers, we predict the existence of several cyclic and branched forms for these molecules. For all the molecular species of interest here, sets of spectroscopic parameters are determined with perturbation theory, which compare quite well with experiment. For l-C_4_H^-^(X^1^{Sigma}^+^), the quartic force field is computed at the coupled cluster level of theory. This force field is derived from full nine-dimensional potential energy surface generated close to the equilibrium geometry of this anion. Finally, we treat the thermochemistry of the hydrogen attachment and the electron attachment reactions that may lead to the formation of the C_4_H^-^ from either C^-^_4_ or C_4_H.
- ID:
- ivo://CDS.VizieR/J/A+A/410/359
- Title:
- Radiative and Auger decay for Fe II-Fe IX
- Short Name:
- J/A+A/410/359
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A detailed analysis of the radiative and Auger de-excitation channels of K-shell vacancy states in Fe II-Fe IX has been carried out. Level energies, wavelengths, A-values, Auger rates and fluorescence yields have been calculated for the lowest fine-structure levels populated by photoionization of the ground state of the parent ion. Different branching ratios, namely K-alpha_2/K-alpha_1, K-beta/K-alpha, KLM/KLL, KMM/KLL, and the total K-shell fluorescence yields, omega_K, obtained in the present work have been compared with other theoretical data and solid-state measurements, finding good general agreement with the latter. The K-alpha_2/K-alpha_1 ratio is found to be sensitive to the excitation mechanism. From these comparisons it has been possible to estimate an accuracy of ~10% for the present transition probabilities.
- ID:
- ivo://CDS.VizieR/J/A+A/529/A103
- Title:
- Radiative losses in solar and stellar coronae
- Short Name:
- J/A+A/529/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The radiative-loss function is an important ingredient in the physics of the solar corona, transition region and flares. We investigate the radiative losses due to the bound-bound transitions and bremsstrahlung and bremsstrahlung for nonthermal {kappa}- and n-distributions. The bound-bound radiative losses are computed by integration of synthetic spectra. Analytical expression for nonthermal bremsstrahlung is derived. The bremsstrahlung is computed numerically using accurate values of the free-free Gaunt factor. We find that the changes in radiative-loss functions due to nonthermal distributions are several times larger than the errors due to missing contribution of the free-bound continuum or errors in atomic data. For {kappa}-distributions, the radiative-loss functions are in general lesser than for Maxwellian distribution, with few exceptions caused by the behavior of Fe. The peaks of the radiative-loss functions are in general flatter. The situation is opposite for n-distributions, for which the radiative-loss functions have higher and narrower peaks. Local minima and maxima of the radiative-loss functions may also be shifted. The contribution from bremsstrahlung change only by few percent except the extreme nonthermal case of {kappa}=2. Stability analysis reveals that the X-ray loops are stable against the radiatively-driven thermal instability.
- ID:
- ivo://CDS.VizieR/J/A+A/436/1141
- Title:
- Radiative rates in Ar XIII, Ar XIV & Ar XV
- Short Name:
- J/A+A/436/1141
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Energies for 524 levels of Ar XIII, 460 levels of Ar XIV and 156 levels of Ar X V have been calculated using the GRAS code of Dyall et al. (1989, Comput. Phys. Commun, 55, 424). Additionally, radiative rates, oscillator strengths, and line strengths are calculated for all electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2) transitions among these levels. Comparisons are made with the limited results available in the literature, and the accuracy of the data is assessed. Our energy levels are estimated to be accurate to better than 1%, whereas results for other parameters are probably accurate to better than 20%. Additionally, the level lifetimes derived from our radiative rates are in excellent agreement with measured values.
