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5 results on '"Department of Physics and Astronomy [Louisville]"'

1. H-He collision-induced satellite in the Lyman alpha profile of DBA white dwarf stars

Author

Grégoire Guillon, John F. Kielkopf, Roberto Linguerri, Majdi Hochlaf, Siyi Xu, Ivan Hubeny, Muneerah Mogren Al Mogren, N. F. Allard, Bilel Mehnen, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Department of Physics and Astronomy [Louisville], University of Louisville, Gemini Observatory, parent, Laboratoire Interdisciplinaire Carnot de Bourgogne [Dijon] (LICB), Université de Bourgogne (UB)-Université de Technologie de Belfort-Montbeliard (UTBM)-Centre National de la Recherche Scientifique (CNRS), Laboratoire Instrumentation, Simulation et Informatique Scientifique (COSYS-LISIS), Université Gustave Eiffel, King Saud University [Riyadh] (KSU), and University of Arizona

Subjects
ATOMIC DATA, LINE: PROFILE, Ab initio, chemistry.chemical_element, BASIS-SET, LINE, EXCITED-STATE, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Spectral line, Physics - Atomic Physics, WHITE DWARF, 0103 physical sciences, Radiative transfer, ABSORPTION, Astrophysics::Solar and Stellar Astrophysics, AB-INITIO CALCULATION, Physics::Atomic Physics, ELECTRONIC-TRANSITION MOMENT, 010306 general physics, STARS: ATMOSPHERE, 010303 astronomy & astrophysics, Helium, Line (formation), POTENTIAL-ENERGY CURVE, Physics, [PHYS]Physics [physics], BALMER-ALPHA, White dwarf, Astronomy and Astrophysics, MOLECULAR DATA, Potential energy, Dipole, chemistry, Astrophysics - Solar and Stellar Astrophysics, Space and Planetary Science, ATOMIC PROCESS, SHAPE, [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], Atomic physics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

The spectra of helium-dominated white dwarf stars with hydrogen in their atmosphere present a distinctive broad feature centered around 1160~\AA\/ in the blue wing of the Lyman-$\alpha$ line. It is extremely apparent in WD 1425+540 recently observed with HST COS. With new theoretical line profiles based on ab initio atomic interaction potentials we show that this feature is a signature of a collision-induced satellite due to an asymptotically forbidden transition. This quasi-molecular spectral satellite is crucial to understanding the asymmetrical shape of Lyman-$\alpha$ seen in this and other white dwarf spectra. Our previous work predicting this absorption feature was limited by molecular potentials that were not adequate to follow the atomic interactions with spectroscopic precision to the asymptotic limit of large separation. A new set of potential energy curves and electronic dipole transition moments for the lowest electronic states of the H--He system were developed to account accurately for the behavior of the atomic interactions at all distances, from the chemical regime within 1~\AA\/ out to where the radiating H atoms are not significantly perturbed by their neighbors. We use a general unified theory of collision-broadened atomic spectral lines to describe a rigorous treatment of hydrogen Lyman-$\alpha$ with these potentials and present a new study of its broadening by radiative collisions of hydrogen and neutral helium. These results enable ab initio modeling of radiative transport in DBA white dwarf atmospheres., Comment: 9 pages, 7 figures

Published
2020
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2. LiHe spectra from brown dwarfs to helium clusters

Author

Grégoire Guillon, John F. Kielkopf, Frank Stienkemeier, Nicole F. Allard, Akira Nakayama, Alexandra Viel, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Division of Chemistry, Graduate School of Science, Hokkaido University [Sapporo, Japan], Physikalisches Institut [Freiburg], Albert-Ludwigs-Universität Freiburg, Department of Physics and Astronomy [Louisville], University of Louisville, Institut de Physique de Rennes (IPR), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS), and Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Atmospheric Science, Line: profiles, Brown dwarf, Aerospace Engineering, chemistry.chemical_element, Astrophysics, Stellar classification, Resonance (particle physics), Spectral line, Stars: atmospheres-brown dwarfs, chemistry.chemical_compound, Astrophysics::Solar and Stellar Astrophysics, LiHe, Spectroscopy, Astrophysics::Galaxy Astrophysics, Helium, Line (formation), Physics, Solar mass, Astronomy and Astrophysics, [PHYS.PHYS.PHYS-SPACE-PH]Physics [physics]/Physics [physics]/Space Physics [physics.space-ph], [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry, Geophysics, chemistry, Helium clusters, Space and Planetary Science, General Earth and Planetary Sciences, Astrophysics::Earth and Planetary Astrophysics, Atomic physics, Atomic and molecular clusters, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

International audience; The detection of Li I lines is the most decisive spectral indicator of substellarity for young brown dwarfs with masses below about 0.06 solar mass. Due to the weakness of the Li resonance lines, it is important to be able to model precisely both their core widths and their wing profiles. This allows an adequate prediction of the mass at which Li lines reappear in the spectra of brown dwarfs for a given age, or reversely an accurate determination of the age of a cluster. We report improved line profiles and the dependence of line width on temperature suitable for modeling substellar atmospheres that were determined from new LiHe molecular potential energies. Over a limited range of density and temperature, comparison with laboratory measurements was used to validate the potential energies which support the spectral line profile theory.

Published
2014
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3. K–H 2 line shapes for the spectra of cool brown dwarfs

Author

John F. Kielkopf, N. F. Allard, Fernand Spiegelman, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut d'Astrophysique de Paris (IAP), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Modélisation, Agrégats, Dynamique (LCPQ) (MAD), Laboratoire de Chimie et Physique Quantiques (LCPQ), Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Institut National des Sciences Appliquées (INSA)-Institut National des Sciences Appliquées (INSA)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut National des Sciences Appliquées - Toulouse (INSA Toulouse), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), Department of Physics and Astronomy [Louisville], University of Louisville, Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC)-Institut de Recherche sur les Systèmes Atomiques et Moléculaires Complexes (IRSAMC), Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)-Institut de Chimie du CNRS (INC), and Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Université Toulouse III - Paul Sabatier (UT3)

Subjects
Physics, Opacity, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], Brown dwarf, Resonance, Astronomy and Astrophysics, Astrophysics, Effective temperature, Stellar classification, 01 natural sciences, Spectral line, Space and Planetary Science, Planet, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010306 general physics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, Line (formation), line: profiles / brown dwarfs
Abstract

International audience; Observations of cooler and cooler brown dwarfs show that the contribution from broadening at many bars pressure is becoming important. The opacity in the red optical to near-IR region under these conditions is dominated by the extremely pressure-broadened wings of the alkali resonance lines, in particular, the K I resonance doublet at 0.77 µm. Collisions with H 2 are preponderant in brown dwarf atmospheres at an effective temperature of about 1000 K; the H 2 perturber densities reach several 10 19 even in Jupiter-mass planets and exceed 10 20 for super-Jupiters and older Y dwarfs. As a consequence, it appears that when the far wing absorption due to alkali atoms in a dense H 2 atmosphere is significant, accurate pressure broadened profiles that are valid at high densities of H 2 should be incorporated into spectral models.

Published
2016
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4. Shift and width of the Balmer series H α line at high electron density in a laser-produced plasma

Author

Nicole F. Allard, John F. Kielkopf, Department of Physics and Astronomy [Louisville], University of Louisville, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)

Subjects
media_common.quotation_subject, Electron, 01 natural sciences, Asymmetry, 010305 fluids & plasmas, law.invention, symbols.namesake, law, 0103 physical sciences, 010306 general physics, Astrophysics::Galaxy Astrophysics, ComputingMilieux_MISCELLANEOUS, Line (formation), media_common, Physics, [PHYS]Physics [physics], Range (particle radiation), Balmer series, Plasma, Condensed Matter Physics, Laser, Atomic and Molecular Physics, and Optics, Pinch, symbols, Atomic physics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

Time-resolved profiles of the Balmer series Hα line emitted by a laser-produced hydrogen plasma have been measured to determine the shift and width for electron densities from below 1018 to above 1020 cm−3 at an average temperature of 28000 K. Fits of the profiles that allow for self-absorption in the plasma yield shifts and widths that are consistent with experiments on lower density and cooler gas-liner pinch plasmas. The width scales as and the shift as between and cm−3. Hα shifts monotonically and nearly linearly to the red with increasing density under the reported conditions. A comparison to theory calculations using exact potentials for shows that an intrinsic asymmetry becomes significant only in the upper limit of this range when a satellite develops in the far red wing.

Published
2014
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5. Temperature dependence of sodium and ionized calcium resonance lines perturbed by helium

Author

Grégoire Guillon, Alexandra Viel, Nicolle F Allard, John F. Kielkopf, Derek Homeier, Institut d'Astrophysique de Paris (IAP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Institut de Physique de Rennes (IPR), Université de Rennes (UR)-Centre National de la Recherche Scientifique (CNRS), Department of Physics and Astronomy [Louisville], University of Louisville, CREATE Project '4023 HELIUM', Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Université de Rennes 1 (UR1), and Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Centre National de la Recherche Scientifique (CNRS)

Subjects
History, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics, Helium, 01 natural sciences, Astronomical spectroscopy, Spectral line, Education, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, 010306 general physics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, [PHYS]Physics [physics], [PHYS.PHYS.PHYS-ATOM-PH]Physics [physics]/Physics [physics]/Atomic Physics [physics.atom-ph], Chemistry, Stellar atmosphere, White dwarf, Astronomy, Planetary system, [PHYS.ASTR.SR]Physics [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR], Accretion (astrophysics), Computer Science Applications, Stars, 13. Climate action, Circumstellar dust, Atomic and molecular collisions, [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph], Astrophysics::Earth and Planetary Astrophysics, Molecular physics, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

International audience; Traces of heavy metals in cool DZ white dwarf stars may be attributed to the accretion of circumstellar dust thought to originate from tidal disruption of rocky parent bodies. Spectra of such stars therefore provide a unique opportunity to study the composition of extrasolar planetary systems. The determination of metal abundances from stellar spectra depends on stellar atmospheric parameters and an accurate prior knowledge of the collision broadening of the line profiles by the most common constituents of the stellar atmosphere. For this purpose, we present theoretical absorption spectra of Na and Ca+ broadened by He for the conditions prevailing in cool white dwarfs.

Published
2014
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