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Emission lines of O bt III in the optical and ultraviolet spectra { } of planetary nebulae
Feibelman, W. A.; Keenan, F. P.; Aller, L. H. +3 more
Recent R-matrix calculations of electron impact excitation rates in O Iii are used to calculate electron temperature and density-dependent emission line ratios R1 = I(4363 Å) / I(4960 Å+ 5007 Å), R2 = I(1661 Å+ 1667 Å) / I(4960 Å+ 5007 Å) and R3 = I(2322 Å) / I(1661 Å+ 1667 Å), for a range of electron temperatures …
Far-infrared [C Ii]/continuum ratio toward the central kiloparsecs of M31. Comparison with that of our Galaxy
Mochizuki, K.
We observed the nearby spiral galaxy M31 with the Long-Wavelength Spectrometer on board the Infrared Space Observatory. Far-infrared line-to-continuum ratios of [C II] / 100 µ m =~ 6 x 10-3 were obtained for the central kiloparsec region along the major axis of the galaxy. These ratios are 2-3 times higher than those in the Galact…
QSO mass constraints from gravitational lensing studies of quasar pairs. The cases of Q1548+114 A & B and Q1148+0055 A & B
Surdej, J.; Sluse, D.; Claeskens, J. -F. +2 more
New constraints on the mass of quasars are derived from gravitational lensing studies of the QSO pairs Q1548+114 A & B and Q1148+0055 A & B, for which new ground-based and Hubble Space Telescope (HST) direct imagery have been obtained. In the case of Q1548+114 A & B, QSO A has been resolved into its host galaxy and a close companion. T…
The effect of different ion fraction datasets on plasma diagnostics
Landini, M.; Landi, E.; Gianetti, D.
In the present work the element abundances in an active region observed on the solar disk are studied using EUV spectral lines observed by the Coronal Diagnostic Spectrometer (CDS) on board of SOHO. Making use of the large number of lines identified in the CDS spectral range and of the instrument imaging capability, the abundances of several eleme…
A comparison of the SAO-Hipparcos reference frames
Arias, E. F.; Cionco, R. G.; Orellana, R. B. +1 more
The reference systems defined by the SAO and Hipparcos catalogues are compared using vector spherical harmonic analysis. The differences between astrometric data in both catalogues have been grouped into different data sets and separate harmonic analysis performed on them. The Fourier coefficients yield estimates of systematic errors in SAO catalo…
Absorption line systems on the line of sight from SN 1987A to SN 1993J and the intergalactic cloud in front of M 81
de Boer, K. S.; Marggraf, O.
We present an extended analysis of the high dispersion IUE spectra of
A survey of selected areas in the galactic plane with ISOCAM
Shipman, R. F.; Price, S. D.; Alard, C. +7 more
Seven 11.6' × 11.6' fields along the inner Galactic plane were imaged by the Infrared Space Observatory's ISOCAM camera to investigate the large scale properties of the Galaxy. We present results from this GPSURVEY program at wavelengths of 10 and 15 µm as well as some complementary observations from the ISOGAL project at 7 µm. Point s…
The central star of the Planetary Nebula NGC 6537
Pottasch, S. R.
The fact that Space Telescope WFPC2 images of the planetary nebula NGC 6537 fail to show the central star is used to derive a limit to its magnitude: it is fainter than a magnitude of 22.4 in the visible. This is used to derive a lower limit to the temperature of the star. The Zanstra temperature is at least 500 000 K. The Energy Balance temperatu…
A study of opacity in SOHO-SUMER and SOHO-CDS spectral observations. II. Atmospheric structure at the solar limb
Fischbacher, G. A.; Loch, S. D.; Summers, H. P.
To model the EUV emission from solar plasma at transition region temperatures it is necessary to take account of both the structure and dynamics of the plasma and the effects of opacity which radiatively couple different points within the plasma. Simple escape probability techniques exist which avoid the need for a full solution of the radiative t…
A thermokinetic study of wave-modulated solar wind electrons using truncated maxwellians
Fahr, H. J.; Chashei, I. V.
Classical kinetic solar wind theories reveal that the solar wind electron distribution function has a delicate influence on the acceleration of the coronal solar wind and its asymptotic velocity. In collisionless kinetics this results from the fact that no hyperbolic electrons with sunward velocities can be expected above the coronal exobase. This…