- ID:
- ivo://CDS.VizieR/J/A+A/657/A121
- Title:
- Collisional effects in blue wing of Balmer-alpha
- Short Name:
- J/A+A/657/A121
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- In order to investigate the near wing of the Lyman-{alpha} line, accurate line profile calculations and molecular data are both required due to the existence of a close line satellite responsible for its asymmetrical shape. Lyman-{alpha} lines observed with the Cosmic Origin Spectograph (COS) on the Hubble Space Telescope (HST) show this peculiarity in the spectra of DBA and DA white dwarf stars. A similar asymmetrical shape in the blue wing can be predicted in the Balmer-{alpha} line of H perturbed by He and H atoms. In continuation with a very recent work on the Lyman-{alpha} line, where the n = 2 potential energies and transition dipole moments from the ground state were determined, we present new accurate H-He potential energies and electronic transition dipole moments involving the molecular states correlated with H(n=3)+He and their transition dipole moments with the states correlated with H(n=2)+He. Those new data and existing molecular data for H(n=2,3)-H are used to provide a theoretical investigation of the collisional effects in the blue wing of the Balmer-{alpha} line of H perturbed by He and H atoms. We note the consequences for the Balmer-{alpha} line shape in the physical conditions found in the cool atmosphere of DZA white dwarfs where helium densities may be as high as 10^21^cm^-3^. This study is undertaken with a unified theory of spectral line broadening valid at very high helium densities.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/531/A103
- Title:
- Collisional excitation of sulfur dioxide
- Short Name:
- J/A+A/531/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present collisional rate coefficients for SO_2_ with ortho and para molecular hydrogen for the physical conditions prevailing in dark molecular clouds. Rate coefficients for the first 31 rotational levels of this species (energies up to 55K) and for temperatures between 5 and 30K are provided. We have found that these rate coefficients are about ten times more than those previously computed for SO_2_ with helium. We calculated the expected emission of the centimeter wavelength lines of SO_2_. We find that the transition connecting the metastable 2_02_ level with the 111 one is in absorption against the cosmic background for a wide range of densities. The 4_04_-3_13_ line is found to be inverted for densities below a few 10^4^cm^-3^. We observed the 1_11_-2_02_ transition with the 100m Green Bank Telescope towards some dark clouds. The line is observed, as expected, in absorption and provides an abundance of SO_2_ in these objects of a few 10^-10^. The potential use of millimeter lines of SO_2_ as tracers of the physical conditions of dark clouds is discussed.
- ID:
- ivo://CDS.VizieR/J/A+A/492/257
- Title:
- Collisional excitation of water in warm media
- Short Name:
- J/A+A/492/257
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The interpretation of water line emission from infrared and submillimetre observations requires a detailed knowledge of collisional rate coefficients over a wide range of levels and temperatures. We attempt to determine rotational and rovibrational rate coefficients for H_2_O colliding with both H_2_ and electrons in warm, molecular gas. Pure rotational rates are derived by extrapolating published data using a new method partly based on the information (phase space) theory of Levine and co-workers. Ro-vibrational rates are obtained using vibrational relaxation data available in the literature and by assuming a complete decoupling of rotation and vibration. Results. Rate coefficients were obtained for the lowest 824 ro-vibrational levels of H_2_O in the temperature range 200-5000K. Our data is expected to be accurate to within a factor of ~5 for the highest rates (>10^-11^cm^3^/s). Smaller rates, including the ro-vibrational ones, should be generally accurate to within an order of magnitude. As a first application of this data, we show that vibrationally excited water emission observed in evolved stars is expected to be at least partly excited by means of collisions.
- ID:
- ivo://CDS.VizieR/VI/51
- Title:
- Collisional Excitation Rates of Formaldehyde
- Short Name:
- VI/51
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Earlier calculations for rotational excitation of formaldehyde H2CO collisions with He atoms are extended to include the 81 lowest rotational levels and kinetic temperatures to 300K.
- ID:
- ivo://CDS.VizieR/J/ApJS/181/572
- Title:
- Collisional ring galaxies atlas
- Short Name:
- J/ApJS/181/572
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog and imaging atlas of classical (collisional) RING galaxies distilled from the Arp-Madore Atlas of Southern Peculiar Galaxies and Associations and supplemented with other known RING galaxies from the published literature. The catalog lists the original host object, compiles available redshifts, and presents newly determined positions for the central (target) galaxy and its nearest companion(s). 127 collisional RING systems are illustrated and their components identified. All of the RINGS have plausible colliders identified; many are radial-velocity confirmed companions. Finally, we make note of the existence of a rare subclass of RING galaxies exemplified by AM 2136-492, double/concentric RING galaxies. These objects are predicted by numerical simulations, but they appear to be quite rare and/or short lived in nature.
- ID:
- ivo://CDS.VizieR/J/AJ/153/165
- Title:
- Collisions of terrestrial worlds
- Short Name:
- J/AJ/153/165
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of an investigation into the occurrence and properties (stellar age and mass trends) of low- mass field stars exhibiting extreme mid-infrared (MIR) excesses (LIR/L*~>~0.01). Stars for the analysis were initially selected from the Motion Verified Red Stars (MoVeRS) catalog of photometric stars with Sloan Digital Sky Survey, 2MASS, and WISE photometry and significant proper motions. We identify 584 stars exhibiting extreme MIR excesses, selected based on an empirical relationship for main-sequence W1-W3 colors. For a small subset of the sample, we show, using spectroscopic tracers of stellar age (H{alpha} and LiI) and luminosity class, that the parent sample is most likely comprised of field dwarfs (>1Gyr). We also develop the Low-mass Kinematics (LoKi) galactic model to estimate the completeness of the extreme MIR excess sample. Using Galactic height as a proxy for stellar age, the completeness-corrected analysis indicates a distinct age dependence for field stars exhibiting extreme MIR excesses. We also find a trend with stellar mass (using r-z color as a proxy). Our findings are consistent with the detected extreme MIR excesses originating from dust created in a short-lived collisional cascade (<100000-years) during a giant impact between two large planetismals or terrestrial planets. These stars with extreme MIR excesses also provide support for planetary collisions being the dominant mechanism in creating the observed Kepler dichotomy (the need for more than a single mode, typically two, to explain the variety of planetary system architectures Kepler has observed), rather than different formation mechanisms.
- ID:
- ivo://CDS.VizieR/VI/148
- Title:
- Collision Strengths for [Co II] Forbidden Lines - SS4
- Short Name:
- VI/148
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The list presents electron collision strengths for the forbidden transitions between the fifteen lowest levels of the singly-ionized cobalt, Co^+^, as a function of the electron energy, in an intermediate coupling scheme using the Breit-Pauli relativistic terms as implemented in an R-matrix atomic scattering code. An atomic target for the R-matrix scattering defined by 26 atomic terms is used in these calculations. The data are particularly useful for analyzing the thermodynamic conditions of supernova ejecta.
- ID:
- ivo://CDS.VizieR/VI/149
- Title:
- Collision Strengths for [Co III] Forbidden Lines - SS5
- Short Name:
- VI/149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The list presents electron collision strengths for the forbidden transitions between the fifteen lowest levels of the doubly-ionized cobalt, Co^2+^, as a function of the electron energy, in an intermediate coupling scheme using the Breit-Pauli relativistic terms as implemented in an R-matrix atomic scattering code. An atomic target for the R-matrix scattering defined by 36 atomic terms is used in these calculations. The data are particularly useful for analyzing the thermodynamic conditions of supernova ejecta.
- ID:
- ivo://CDS.VizieR/J/ApJ/788/24
- Title:
- Collision strengths for transitions in Fe VII
- Short Name:
- J/ApJ/788/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Extensive calculations have been performed for electron impact excitation collision strengths and oscillator strengths for the Fe VII extreme ultraviolet lines of astrophysical importance. The collision strengths for fine-structure transitions are calculated in the B-spline Breit-Pauli R-matrix approach. The target wavefunctions have been calculated in the multiconfiguration Hartree-Fock method with term-dependent non-orthogonal orbitals. The close-coupling expansion includes 189 fine-structure levels of Fe VII belonging to terms of the ground 3p^6^ 3d^2^ and excited 3p^5^ 3d^3^, 3p^6^ 3d4l, 3p^6^ 3d5s, and 3p^6^ 3d5p configurations. The effective collision strengths are determined from the electron excitation collision strengths by integration over a Maxwellian distribution of electron velocities. The effective collision strengths are provided for 17766 fine-structure transitions at electron temperatures from 10^4^ to 10^7^ K. Our results normally agree with the previous R-matrix frame-transformation calculations by Witthoeft & Badnell (2008A&A...481..543W). However, there are important differences for some transitions with the previous calculations. The corrections to the previous results are mainly due to more extensive expansions for the Fe VII target states.
- ID:
- ivo://CDS.VizieR/J/ApJ/812/174
- Title:
- Collision strengths in FeIX
- Short Name:
- J/ApJ/812/174
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Collision strengths and thermally averaged collision strengths for a large number of extreme-ultraviolet lines of FeIX arising by electron impact have been reported. The thermally averaged collision strengths are calculated at electron temperatures in the range 10^4^-10^7^K for the 122043 forbidden and allowed transitions between the 370 fine-structure levels. The atomic parameters for FeIX play an important role in modeling of various astrophysical plasmas, including especially the solar corona. The B-spline Breit-Pauli R-matrix method has been used in the calculation of collision strengths. The target wave functions and transition probabilities have been determined by combining the multiconfiguration Hartree-Fock method with the B-spline box-based multichannel expansions. We have included 370 fine-structure levels of FeIX in the energy region up to 3s^2^3p^5^5s states. The close-coupling expansion includes levels of the 3s^2^3p^6^, 3s^2^3p^5^3d, 4l, 5s, 3s3p^6^3d, 4s, 4p, 3s^2^3p^4^3d^2^, 3s3p^5^3d^2^ configurations and some low-lying levels of the 3s^2^3p^3^3d^3^ configuration in our collision strengths and transition probabilities calculations. There is a good agreement with the previous R-matrix collision strength calculations by Storey et al. (2002, J/A+A/394/753) and Del Zanna et al. (2014, J/A+A/565/A77) for transitions between the lowest 17 levels of the 3s^2^3p^6^, 3s^2^3p^5^3d and 3s3p^6^3d configurations, especially for electron temperatures logT(K)>=5.0. The transitions between the first 17 levels are dominated by Rydberg series of resonances converging to the levels of the 3s^2^3p^4^3d^2^ configuration. The present results and the calculation of Del Zanna et al. show significant differences for many weaker forbidden and intercombination transitions with thermally averaged collision strengths smaller than 0.01.