- ID:
- ivo://CDS.VizieR/J/ApJ/873/L5
- Title:
- Magnetic field measurements of Ap/Bp stars
- Short Name:
- J/ApJ/873/L5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on magnetic field measurements of 157 chemically peculiar A/B stars (Ap/Bp) based on resolved, magnetically split absorption lines present in H-band spectra provided by the Sloan Digital Sky Survey (SDSS)/Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. These stars represent the extreme magnetic end of a still-growing sample of >900 Ap/Bp stars selected among the APOGEE telluric standard stars as those with CeIII absorption lines and/or literature Ap/Bp classifications. The lines most frequently resolved into their split components for these stars in the H-band pertain primarily pertain to CeIII, CrII, FeI, MnII, SiI, and CaII, in addition to one or more unidentified ions. Using mean magnetic field modulus (<B>) estimates for transitions with known Lande factors, we estimate effective Lande factors for 5 CeIII lines and 15 unknown lines and proceed to measure <B> of 157 stars, only 3 of which have previous literature estimates of <B>. This 183% increase in the number of Ap/Bp stars for which <B> has been measured is a result of the large number of stars observed by SDSS/APOGEE, extension of high-resolution Ap/Bp star observations to fainter magnitudes, and the advantages of long wavelengths for resolving magnetically split lines. With <B>~25kG, the star 2MASS J02563098+4534239 is currently the most magnetic star of the SDSS/APOGEE sample. Effective Lande factors, representative line profiles, and magnetic field moduli are presented. The validity of the results is supported using optical, high-resolution, follow-up spectra for 29 of the stars.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/387/1146
- Title:
- M1 and E2 emission lines in K-like ions
- Short Name:
- J/A+A/387/1146
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Relativistic Quantum Defect Orbital (RQDO) calculations of transition probabilities for E2 (electric quadrupole) and M1 (magnetic dipole) forbidden transition in the potassium sequence have been performed. Intensities for the higher ions are reported, to our knowledge, for the first time, as they are potentially important for the study of the plasma in astrophysical objects and fusion devices.
- ID:
- ivo://CDS.VizieR/J/ApJS/228/15
- Title:
- MARVEL analysis of TiO energy levels
- Short Name:
- J/ApJS/228/15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate, experimental rovibronic energy levels, with associated labels and uncertainties, are reported for 11 low-lying electronic states of the diatomic ^48^Ti^16^O molecule, determined using the MARVEL (Measured Active Rotational-Vibrational Energy Levels) algorithm. All levels are based on lines corresponding to critically reviewed and validated high-resolution experimental spectra taken from 24 literature sources. The transition data are in the 2-22160cm^-1^ region. Out of the 49679 measured transitions, 43885 are triplet-triplet, 5710 are singlet-singlet, and 84 are triplet-singlet transitions. A careful analysis of the resulting experimental spectroscopic network (SN) allows 48590 transitions to be validated. The transitions determine 93 vibrational band origins of ^48^Ti^16^O, including 71 triplet and 22 singlet ones. There are 276 (73) triplet-triplet (singlet-singlet) band-heads derived from Marvel experimental energies, 123(38) of which have never been assigned in low- or high-resolution experiments. The highest J value, where J stands for the total angular momentum, for which an energy level is validated is 163. The number of experimentally derived triplet and singlet ^48^Ti^16^O rovibrational energy levels is 8682 and 1882, respectively. The lists of validated lines and levels for ^48^Ti^16^O are deposited in the supporting information to this paper.
- ID:
- ivo://CDS.VizieR/J/ApJS/216/21
- Title:
- Matrix elements and energies for Hydrogen
- Short Name:
- J/ApJS/216/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The matrix elements and energies needed to calculate vibrational-rotational state resolved cross sections and rate coefficients for radiative association of H and H^+^ and for photodissociation of H_2_^+^ are presented for applications to simulations of chemistry in the early universe and to stellar atmospheres.
- ID:
- ivo://CDS.VizieR/J/ApJS/226/14
- Title:
- MBPT calculations for Ne-like ions (CrXV to KrXXVII)
- Short Name:
- J/ApJS/226/14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Level energies, wavelengths, electric dipole, magnetic dipole, electric quadrupole, and magnetic quadrupole transition rates, oscillator strengths, and line strengths from combined relativistic configuration interaction and many-body perturbation (MBPT) calculations are reported for the 201 fine-structure states of the 2s^2^2p^6^, 2s^2^2p^5^3l, 2s2p^6^3l, 2s^2^2p^5^4l, 2s2p^6^4l, 2s^2^2p^5^5l, and 2s^2^2p^5^6l configurations in all Ne-like ions between CrXV and KrXXVII. Calculated level energies and transition data are compared with experiments from the National Institute of Standards and Technology (NIST) and CHIANTI databases, and other recent benchmark calculations. The mean energy difference with the NIST experiments is only 0.05%. The present calculations significantly increase the amount of accurate spectroscopic data for the n>3 states in a number of Ne-like ions of astrophysical interest. A complete data set should be helpful for analyzing new observations from solar and other astrophysical sources, and is also likely to be useful for modeling and diagnosing a variety of plasmas, including astronomical and fusion plasma.
- ID:
- ivo://CDS.VizieR/J/A+A/639/A25
- Title:
- MCDHF calculations of Lande g-factors
- Short Name:
- J/A+A/639/A25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Lande g-factor is an important parameter in astrophysical spectropolarimetry, used to characterize the response of a line to a given value of the magnetic field. The purpose of this paper is to present accurate Lande g-factors for states in BII, CI-IV, AlI-II, SiI-IV, PII, SII, ClIII, ArIV, CaI, TiII, ZrIII, and SnII. The multiconfiguration Dirac-Hartree-Fock and relativistic configuration interaction methods, which are implemented in the general-purpose relativistic atomic structure package GRASP2K, are employed in the present work to compute the Lande g-factors for states in BII, CI-IV, AlI-II, SiI-IV, PII, SII, ClIII, ArIV, CaI, TiII, ZrIII, and SnII. The accuracy of the wave functions for the states, and thus the accuracy of the resulting Lande g-factors, is evaluated by comparing the computed excitation energies and energy separations with the National Institute of Standards and Technology (NIST) recommended data. All excitation energies are in very good agreement with the NIST values except for TiII, which has an average difference of 1.06%. The average uncertainty of the energy separations is well below 1% except for the even states of AlI; odd states of SiI, CaI, TiII, ZrIII; and even states of SnII for which the relative differences range between 1% and 2%. Comparisons of the computed Lande g-factors are made with available NIST data and experimental values. Analysing the $LS$-composition of the wave functions, we quantify the departures from $LS$-coupling and summarize the states for which there is a difference of more than 10% between the computed Lande g-factor and the Lande g-factor in pure $LS$-coupling. Finally, we compare the computed Lande g-factors with values from the Kurucz database.
- ID:
- ivo://CDS.VizieR/J/A+A/643/A156
- Title:
- MCDHF calculations of TiII
- Short Name:
- J/A+A/643/A156
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Accurate atomic data for TiII are essential for abundance analyses in astronomical objects. The aim of this work is to provide accurate and extensive results of oscillator strengths and lifetimes for TiII. The multiconfiguration Dirac-Hartree-Fock (MCDHF) and relativistic configuration interaction (RCI) methods, which are implemented in the general-purpose relativistic atomic structure package GRASP2018, were used in the present work. In the final RCI calculations, the transverse-photon (Breit) interaction, the vacuum polarization, and the self-energy corrections were included. Energy levels and transition data were calculated for the 99 lowest states in TiII. Calculated excitation energies are found to be in good agreement with experimental data from the Atomic Spectra Database (ASD) of the National Institute of Standards and Technology (NIST) based on the study by Huldt et al. (Physica Scripta 25, 401 (1982)). Lifetimes and transition data, e.g. line strengths, weighted oscillator strengths, and transition probabilities for radiative electric dipole (E1),magnetic dipole (M1), and electric quadrupole (E2) transitions are given and extensively compared with results from previous calculations and measurements, when available. The present theoretical results of the oscillator strengths are in overall better agreement with values from the experiments than the other theoretical predictions. The computed lifetimes of the odd states are in excellent agreement with the measured lifetimes. Finally, we suggest a relabelling of the 3d^2^(^1^_2_D)4p y^2^D_3/2_^o^ and z^2^P_3/2_^o^ levels.
- ID:
- ivo://CDS.VizieR/J/MNRAS/501/1440
- Title:
- MCDHF radiative parameters for CeII-IV
- Short Name:
- J/MNRAS/501/1440
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Large-scale calculations of atomic structures and radiative properties have been carried out for singly, doubly- and trebly ionized cerium. For this purpose, the purely relativistic multiconfiguration Dirac-Hartree-Fock (MCDHF) method was used, taking into account the effects of valence-valence and core-valence electronic correlations in detail. The results obtained were then used to calculate the expansion opacities characterizing the kilonovae observed as a result of neutron star mergers. Comparisons with previously published experimental and theoretical studies have shown that the results presented in this work are the most complete currently available, in terms of quantity and quality, concerning the atomic data and monochromatic opacities for CeII, CeIII and CeIV ions.
- ID:
- ivo://CDS.VizieR/J/ApJ/789/2
- Title:
- Methane partition function
- Short Name:
- J/ApJ/789/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The paper describes the construction of complete sets of hot methane lines based on accurate ab initio potential and dipole moment surfaces and extensive first-principle calculations. Four line lists spanning the [0-5000]/cm infrared region were built at T = 500, 1000, 1500, and 2000 K. For each of these four temperatures, we have constructed two versions of line lists: a version for high-resolution applications containing strong and medium lines and a full version appropriate for low-resolution opacity calculations. A comparison with available empirical databases is discussed in detail for both cold and hot bands giving a very good agreement for line positions, typically <0.1-0.5/cm and ~5% for intensities of strong lines. Together with numerical tests using various basis sets, this confirms the computational convergence of our results for the most important lines, which is the major issue for theoretical spectra predictions. We showed that transitions with lower state energies up to 14,000/cm could give significant contributions to the methane opacity and have to be systematically taken into account. Our list at 2000 K calculated up to J = 50 contains 11.5 billion transitions for I > 10^-29^ cm/mol. These new lists are expected to be quantitatively accurate with respect to the precision of available and currently planned observations of astrophysical objects with improved spectral resolution.
- ID:
- ivo://CDS.VizieR/J/MNRAS/409/29
- Title:
- Methanol line formation in outflow sources
- Short Name:
- J/MNRAS/409/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first calculations of the spectrum of methanol, arising in shock waves in molecular outflows. The small grid of shock wave models that we have computed incorporates the results of very recent computations of the rate coefficients for the collisional excitation of methanol by ortho- and para-H2 and by He. The two strongest transitions, one of A- and the other of E-type methanol, are masers that have been observed in a Class I methanol maser source, which is believed to be related to a molecular outflow. The same collisional propensities that give rise to population inversion and maser action can, in other transitions, lead to population anti-inversion and the lines appearing in absorption against the cosmic background radiation. We attempted to model specifically the outflow source L1157 B1, in which transitions of methanol have been observed recently by means of the Herschel satellite. Comparison with the predictions of the shock wave models is complicated by uncertainty in the value of the beam filling factor that should be adopted.
