Theoretical astrophysics and plasma physics at RPC

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A study of velocity fields in the transition region of ε Eri (K2 V)

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY 341:2 (2003) 517-533

Authors:

SA Sim, C Jordan
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A transient event in lines of Ne V, VI and VII

ASTRONOMY & ASTROPHYSICS 401:3 (2003) 1131-1142

Authors:

ER Houdebine, C Jordan
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An atlas of Hubble Space Telescope spectra and images of nearby spiral galaxies

ASTRONOMICAL JOURNAL 126:2 (2003) 742-761

Authors:

MA Hughes, A Alonso-Herrero, D Axon, C Scarlata, J Atkinson, D Batcheldor, J Binney, A Capetti, CM Carollo, L Dressel, J Gerssen, D Macchetto, W Maciejewski, A Marconi, M Merrifield, M Ruiz, W Sparks, M Stiavelli, Z Tsvetanov, R van der Marel
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Is there really a black hole at the center of NGC 4041? Constraints from gas kinematics

ASTROPHYSICAL JOURNAL 586:2 (2003) 868-890

Authors:

A Marconi, DJ Axon, A Capetti, W Maciejewski, J Atkinson, D Batcheldor, J Binney, M Carollo, L Dressel, H Ford, J Gerssen, MA Hughes, D Macchetto, MR Merrifield, C Scarlata, W Sparks, M Stiavelli, Z Tsvetanov, RP van der Marel
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New constraints on the formation of the helium lines

EAS PUBLICATIONS 9 (2003) 365-370

Authors:

ER Houdebine, GR Smith, C Jordan

Abstract:

We analyse observations of the helium lines obtained with CDS onboard SOHO. The He I 584.3 Angstrom/O III intensity ratio shows a lower limit and an upper limit that decrease with increasing 0 in intensity. At low O III intensities this ratio increases significantly. An upper limit arises naturally if the enhancement mechanism involves turbulent motions transporting the helium atoms and ions through the steep transition region temperature gradient. The He I 537.0-Angstrom/He I 584.3-Angstrom and He II 303.8-Angstrom/He I 584.3-Angstrom intensity ratios both decrease as the He I 584.3-Angstrom line intensity increases. The values of the line ratios support the enhancement of the helium lines by turbulent motions, but appear to rule out the enhancement due to excitation by non-thermal coronal electrons.
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