- ID:
- ivo://CDS.VizieR/J/A+A/624/A94
- Title:
- The role of the host star's metallicity
- Short Name:
- J/A+A/624/A94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Most of our current understanding of the planet formation mechanism is based on the planet metallicity correlation derived mostly from solar-type stars harbouring gas-giant planets. To achieve a more extensive grasp on the substellar formation process, we aim to analyse in terms of their metallicity a diverse sample of stars (in terms of mass and spectral type) covering the whole range of possible outcomes of the planet formation process (from planetesimals to brown dwarfs and low-mass binaries). Our methodology is based on the use of high-precision stellar parameters derived by our own group in previous works from high-resolution spectra by using the iron ionisation and equilibrium conditions. All values were derived in an homogeneous way, except for the M dwarfs where a methodology based on the use of pseudo equivalent widths of spectral features was used. Our results show that as the mass of the substellar companion increases the metallicity of the host star tends to lower values. The same trend is maintained when analysing stars with low-mass stellar companions and a tendency towards a wide range of host star's metallicity is found for systems with low-mass planets. We also confirm that more massive planets tend to orbit around more massive stars. The core-accretion formation mechanism for planet formation achieves its maximum efficiency for planets with masses in the range 0.2 and 2M_{Jup}_. Substellar objects with higher masses have higher probabilities of being formed as stars. Low-mass planets and planetesimals might be formed by core-accretion even around low-metallicity stars.
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- ID:
- ivo://CDS.VizieR/J/A+A/659/A111
- Title:
- The rotational spectrum of acrylamide
- Short Name:
- J/A+A/659/A111
- Date:
- 15 Mar 2022 06:07:15
- Publisher:
- CDS
- Description:
- Numerous complex organic molecules have been detected in the universe and among them are amides, which are considered as prime models for species containing a peptide linkage. In its backbone, acrylamide (CH_2_CHC(O)NH_2_) bears not only the peptide bond, but also the vinyl functional group that is a common structural feature in many interstellar compounds. This makes acrylamide an interesting candidate for searches in the interstellar medium. In addition, a tentative detection of the related molecule propionamide (C_2_H_5_C(O)NH_2_) has been recently claimed toward Sgr B2(N). The aim of this work is to extend the knowledge of the laboratory rotational spectrum of acrylamide to higher frequencies, which would make it possible to conduct a rigorous search for interstellar signatures of this amide using millimeter wave astronomy. We measured and analyzed the rotational spectrum of acrylamide between 75 and 480GHz. We searched for emission of acrylamide in the imaging spectral line survey ReMoCA performed with the Atacama Large Millimeter/submillimeter Array toward Sgr B2(N). We also searched for propionamide in the same source. The astronomical spectra were analyzed under the assumption of local thermodynamic equilibrium. We report accurate laboratory measurements and analyses of thousands of rotational transitions in the ground state and two excited vibrational states of the most stable syn form of acrylamide. In addition, we report an extensive set of rotational transitions for the less stable skew conformer. Tunneling through a low energy barrier between two symmetrically equivalent configurations has been revealed for this higher-energy species. Neither acrylamide nor propionamide were detected toward the two main hot molecular cores of Sgr B2(N). We did not detect propionamide either toward a position located to the east of the main hot core, thereby undermining the recent claim of its interstellar detection toward this position. We find that acrylamide and propionamide are at least 26 and 14 times less abundant, respectively, than acetamide toward the main hot core Sgr B2(N1S), and at least 6 and 3 times less abundant, respectively, than acetamide toward the secondary hot core Sgr B2(N2). A comparison with results of astrochemical kinetics model for related species suggests that acrylamide may be a few hundred times less abundant than acetamide, corresponding to a value that is at least an order of magnitude lower than the observational upper limits. Propionamide may be as little as only a factor of two less abundant than the upper limit derived toward Sgr B2(N1S). Lastly, the spectroscopic data presented in this work will aid future searches of acrylamide in space.
- ID:
- ivo://CDS.VizieR/J/A+A/657/A99
- Title:
- The rotational spectrum of glycinamide
- Short Name:
- J/A+A/657/A99
- Date:
- 21 Mar 2022 09:35:44
- Publisher:
- CDS
- Description:
- Glycinamide (NH_2_CH_2_C(O)NH_2_) is considered to be one of the possible precursors of the simplest amino acid glycine. Its only rotational spectrum reported so far has been in the cm-wave region on a laser-ablation generated supersonic expansion sample. The aim of this work is to extend the laboratory spectrum of glycinamide into the millimetre wave region to support its searches in the interstellar medium and to perform the first check for its presence in the high-mass star forming region Sagittarius B2(N). Glycinamide was synthesised chemically and was studied with broadband rotational spectroscopy in the 90-329 GHz region with the sample in slow flow at 50{deg}C. Tunneling across a low energy barrier between two symmetry equivalent configurations of the molecule resulted in splitting of each vibrational state and many perturbations in associated rotational energy levels, requiring careful coupled state fits for each vibrational doublet. We searched for emission of glycinamide in the imaging spectral line survey ReMoCA performed with the Atacama Large Millimetre/submillimetre Array toward Sgr B2(N). The astronomical spectra were analysed under the assumption of local thermodynamic equilibrium. We report the first analysis of the mm-wave rotational spectrum of glycinamide, resulting in fitting to experimental measurement accuracy of over 1200 assigned and measured transition frequencies for the ground state tunneling doublet, of many lines for tunneling doublets for two singly excited vibrational states, and determination of precise vibrational separation in each doublet. We did not detect emission from glycinamide in the hot molecular core Sgr B2(N1S). We derived a column density upper limit of 1.5x10^16^cm^-2^, which implies that glycinamide is at least seven times less abundant than aminoacetonitrile and 1.8 times less abundant than urea in this source.
- ID:
- ivo://CDS.VizieR/J/ApJ/530/783
- Title:
- The r-process enriched giant HD 115444
- Short Name:
- J/ApJ/530/783
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New high-resolution, very high signal-to-noise spectra of ultrametal-poor (UMP) giant stars HD 115444 and HD 122563 have been gathered with the High-Resolution Echelle Spectrometer of the McDonald Observatory 2.7 m telescope. With these spectra, line identification and model atmosphere analyses have been conducted, emphasizing the neutron-capture elements. Twenty elements with Z > 30 have been identified in the spectrum of HD 115444. This star is known to have overabundances of the neutron-capture elements, but it has lacked a detailed analysis necessary to compare with nucleosynthesis predictions. The new study features a line-by-line differential abundance comparison of HD 115444 with the bright, well-studied halo giant HD 122563.
- ID:
- ivo://CDS.VizieR/J/ApJS/183/17
- Title:
- The SDSS DR5/XMM-Newton quasar survey
- Short Name:
- J/ApJS/183/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 792 Fifth Data Release Sloan Digital Sky Survey quasars with optical spectra that have been observed serendipitously in the X-rays with the XMM-Newton. These quasars cover a redshift range of z=0.11-5.41 and a magnitude range of i=15.3-20.7. Substantial numbers of radio-loud (70) and broad absorption line (51) quasars exist within this sample. Significant X-ray detections at >=2{sigma} account for 87% of the sample (685 quasars), and 473 quasars are detected at >=6{sigma}, sufficient to allow X-ray spectral fits. For detected sources, ~60% have X-ray fluxes between F_2-10keV_=(1-10)x10^-14^erg/cm^2^/s. We fit a single power law, a fixed power law with intrinsic absorption left free to vary, and an absorbed power-law model to all quasars with X-ray signal-to-noise ratio >=6, resulting in a weighted mean photon index {Gamma}=1.91+/-0.08, with an intrinsic dispersion {sigma}_{Gamma}_=0.38.
- ID:
- ivo://CDS.VizieR/J/ApJS/241/34
- Title:
- The SDSS Reverberation Mapping (SDSS-RM) project
- Short Name:
- J/ApJS/241/34
- Date:
- 07 Mar 2022 07:38:42
- Publisher:
- CDS
- Description:
- We present a detailed characterization of the 849 broad-line quasars from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project. Our quasar sample covers a redshift range of 0.1<z<4.5 and is flux-limited to i_PSF_<21.7 without any other cuts on quasar properties. The main sample characterization includes: (1) spectral measurements of the continuum and broad emission lines for individual objects from the coadded first-season spectroscopy in 2014, (2) identification of broad and narrow absorption lines in the spectra, and (3) optical variability properties for continuum and broad lines from multi-epoch spectroscopy. We provide improved systemic redshift estimates for all quasars and demonstrate the effects of the signal-to-noise ratio on the spectral measurements. We compile measured properties for all 849 quasars along with supplemental multi-wavelength data for subsets of our sample from other surveys. The SDSS-RM sample probes a diverse range in quasar properties and shows well-detected continuum and broad-line variability for many objects from first-season monitoring data. The compiled properties serve as the benchmark for follow-up work based on SDSS-RM data.
2837. The solar CNO abundances
- ID:
- ivo://CDS.VizieR/J/A+A/656/A113
- Title:
- The solar CNO abundances
- Short Name:
- J/A+A/656/A113
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Carbon, nitrogen, and oxygen are the fourth, sixth, and third most abundant elements in the Sun. Their abundances remain hotly debated due to the so-called solar modelling problem that has persisted for almost 20 years. We revisit this issue by presenting a homogeneous analysis of 408 molecular lines across 12 diagnostic groups, observed in the solar intensity spectrum. Using a realistic 3D radiative-hydrodynamic model solar photosphere and local thermodynamic equilibrium (LTE) line formation, we find log{epsilon}C=8.47+/-0.02, log{epsilon}N=7.89+/-0.04, and log{epsilon}O=8.70+/-0.04. The stipulated uncertainties mainly reflect the sensitivity of the results to the model atmosphere; this sensitivity is correlated between the different diagnostic groups, which all agree with the mean result to within 0.03dex. For carbon and oxygen, the molecular results are in excellent agreement with our 3D non-LTE analyses of atomic lines. For nitrogen, however, the molecular indicators give a 0.12dex larger abundance than the atomic indicators, and our best estimate of the solar nitrogen abundance is given by the mean: 7.83dex. The solar oxygen abundance advocated here is close to our earlier determination of 8.69dex, and so the present results do not significantly alleviate the solar modelling problem.
- ID:
- ivo://CDS.VizieR/J/A+A/643/A146
- Title:
- The solar gravitational redshift
- Short Name:
- J/A+A/643/A146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The General Theory of Relativity predicts the redshift of spectral lines in the solar photosphere, as a consequence of the gravitational potential of the Sun. This effect can be measured from a solar disk-integrated flux spectrum of the Sun's reflected light on solar system bodies. The laser frequency comb (LFC) calibration system attached to the HARPS spectrograph offers the possibility to perform an accurate measurement of the solar gravitational redshift (GRS) by observing the Moon or other solar system bodies. We have analysed the line shift observed in Fe absorption lines from five high-quality HARPS-LFC spectra of the Moon. We select an initial sample of 326 photospheric Fe lines in the spectral range 476-585nm and measure their line positions and equivalent widths (EWs). Accurate line shifts are derived from the wavelength position of the core of the lines compared with the laboratory wavelengths of Fe lines. We also use a CO^5^BOLD 3D hydrodynamical model atmosphere of the Sun to compute 3D synthetic line profiles of a subsample of about 200 spectral Fe lines centred at their laboratory wavelengths. We fit the observed relatively weak spectral Fe lines (with EW<180m{AA}) with the 3D synthetic profiles. Convective motions in the solar photosphere do not affect the line cores of Fe lines stronger than about 150m{AA}. In our sample, only 15 FeI lines have EWs in the range 150<EW(m{AA})<550, providing a measurement of the solar GRS at 639+/-14m/s, consistent with the expected theoretical value on Earth of 633.1m/s. A final sample of about 98 weak Fe lines with EW<180m{AA} allows us to derive a mean global line shift of 638+/-6m/s in agreement with the theoretical solar GRS. These are the most accurate measurements of the solar GRS so far. Ultrastable spectrographs calibrated with the LFC over a larger spectral range, such as HARPS or ESPRESSO, together with a further improvement on the laboratory wavelengths, could provide a more robust measurement of the solar GRS and further tests for the 3D hydrodynamical models.
- ID:
- ivo://CDS.VizieR/J/AJ/161/172
- Title:
- The Solar Neighborhood. XLVII. Mdwarfs with STIS
- Short Name:
- J/AJ/161/172
- Date:
- 18 Jan 2022
- Publisher:
- CDS
- Description:
- We use HST/STIS optical spectroscopy of 10 M-dwarfs in five closely separated binary systems to test models of M-dwarf structure and evolution. Individual dynamical masses ranging from 0.083 to 0.405M{sun} for all stars are known from previous work. We first derive temperature, radius, luminosity, surface gravity, and metallicity by fitting the BT-Settl atmospheric models. We verify that our methodology agrees with empirical results from long-baseline optical interferometry for stars of similar spectral types. We then test whether or not evolutionary models can predict those quantities given the stars' known dynamical masses and the conditions of coevality and equal metallicity within each binary system. We apply this test to five different evolutionary model sets: the Dartmouth models, the MESA/MIST models, the models of Baraffe et al., the PARSEC models, and the YaPSI models. We find marginal agreement between evolutionary model predictions and observations, with few cases where the models respect the condition of coevality in a self-consistent manner. We discuss the pros and cons of each family of models and compare their predictive power.
- ID:
- ivo://CDS.VizieR/J/ApJS/207/13
- Title:
- The spectrum and term analysis of V II
- Short Name:
- J/ApJS/207/13
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spectrum and extended term analysis of V II are presented. Fourier transform spectrometry was used to record high resolution spectra of singly ionized vanadium in the region 1492-5800 {AA} (67020-17260/cm) with vanadium-neon and vanadium-argon hollow cathode lamps as sources. The wavenumber uncertainty for the center of gravity of the strongest lines is typically 0.002/cm, an improvement of an order of magnitude over previous measurements. Most of the lines exhibit partly resolved hyperfine structure. The V II energy levels in the 1985 compilation of Sugar and Corliss have been confirmed and revised, with the exception of the high-lying 4f levels and eight of the lower levels. Thirty-nine of the additional eighty-five high levels published by Iglesias et al. (1988, Publicaciones del Instituto Optica Daza de Valdes Madrid, 47, 1) have also been confirmed and revised, and three of their missing levels have been found. The energy uncertainty of the revised levels has been reduced by about an order of magnitude. In total, 176 even levels and 233 odd levels are presented.
