Ultraviolet Stellar Spectra and Related Ground-Based Observations

Two years ago, just before the Prague meeting of the International Astronomical Union, Armin Deutsch made the bold suggestion that the space spectroscopists hold a joint symposium with the ground-based observers. At that time the rocket observa­ tions of stellar spectra seemed too meagre to make such a meeting worthwhile, but we proceeded in the hope that there would be significant new results available by 1969. IAU Commissions 29 and 44, on Stellar Spectra and Observations from Outside the Terrestrial Atmosphere respectively, agreed to sponsor the symposium so that the organization was given to the Joint Working Group of these commissions. Conse­ quently, the Organizing Committee, which met first in Prague, consisted of A. Deutsch, M. W. Feast, L. Houziaux, V. G. Kurt, N. G. Roman, J. Sahade, A. B. Underhill, and R. Wilson, with myself as Chairman. Later COSP AR was invited to join in spon­ soring the symposium and T. Chubb was added as their representative. We were specially pleased when C. de Jager invited us to the Netherlands and offered the services of the Utrecht Observatory for the local organization. He suggested we hold the meeting at the new Lunteren Conference Centre located in a wooded area some 35 km east of Utrecht. The modern facilities of the Centre and the hospi­ tality of its staff contributed much to the enjoyment of our four days there.

I / Stellar Fluxes.- A. Absolute Calibration.- 1. Absolute intensity calibration methods in the vacuum UV region.- 2. An investigation of the properties of vacuum-ultraviolet radiation detectors (Abstract).- 3. Recent absolute calibration work at Palomar Mountain.- 4. General discussion (On calibration methods).- B. Interstellar Extinction.- 1. Interstellar extinction (Introductory lecture).- 2. Ultraviolet interstellar extinction from a comparison of ? Persei and ? Pesei.- 3. Observations of interstellar extinction in the ultraviolet with the OAO satellite.- 4. On dielectric models of interstellar grains.- 5. Extinction curves for graphite-silicate grain mixtures.- 6. Measurement of interstellar extinction in emission line stars.- 7. The interstellar extinction curve from 4000 Å to 6500 Å.- C. Theoretical Models for Stellar Fluxes.- 1. The effective temperatures of the O stars.- 2. The effect of Silicon and Carbon opacity on ultraviolet stellar spectra.- D. Observed Stellar Fluxes.- 1. Review of ultraviolet and visual continuum observations and comparisons with models.- 2. The stellar temperature scale from 05 to A0.- 3. On ultraviolet fluxes, bolometric corrections and effective temperatures of late B to F stars.- 4. Far-ultraviolet intensities of Orion stars.- 5. Ultraviolet photometry of stars obtained with the Celescope experiment in the Orbiting Astronomical Observatory.- 6. Photographic magnitudes of 201 stars at 2600 Å.- 7. Spectrophotometrie integree des galaxies proches dans l’ultraviolet (expérience Persée).- 8. Low resolution stellar spectrophotometrie observations in the region 1500 Å–3000 Å.- 9. Absolute stellar photometry in the region 1200 Å–3000 Å.- 10. Preliminary note on the astronomical satellite Kosmos 215.- 11. Ultraviolet photometry of stars from OSO II.- 12. The ultraviolet solar opacity.- II / Stellar Line Spectra.- A. Rocket and Satellite Observations of Ultraviolet Spectra.- 1. Observations of ultraviolet stellar spectra.- 2. Photoelectric rocket spectra at 10 Å resolution (Abstract).- 3. Rocket spectroscopy of ? Puppis below 1100 Å.- 4. Observations of strong stellar lines with the OAO.- 5. The far-ultraviolet spectrum of ? Cassiopeiae.- 6. UV spectrophotometry of Canopus from Gemini XI.- B. Ground-Based Observations of Spectra Relevant to the Ultraviolet.- 1. Review of ground-based observations of spectra relevant to the ultraviolet.- 2. Chromospheric activity in red giants, and related phenomena.- 3. Mass loss from early-type stars.- C. Theory Relevant to UV Spectra.- 1. A discussion of the theory for interpreting ultraviolet stellar spectra.- 2. Possibility of fluorescence phenomena in the ultraviolet spectrum of symbiotic stars and long period variables.- 3. Radiative acceleration and ultraviolet resonance line profiles in OB supergiants.- 4. Stellar-wind theory for O and B stars (Abstract).- D. The Sun — a Typical G2V Star.- 1. Review of astrophysical conclusions from the UV solar spectra.- 2. Resonance lines in the solar chromosphere.- 3. On the contribution of solar activity to the ultraviolet spectrum of the Sun.- 4. Intensity distribution in the Lyman-? line at the solar limb.- 5. A high-resolution solar spectrum 2000 Å–2200 Å.- 6. Fabry-Pérot interferograms of the solar MgII resonance lines.- III / Interstellar Absorption and Emission.- A. Absorption Lines.- 1. Observations of interstellar Lyman-? absorption.- 2. Observations of interstellar Lyman-? with the Orbiting Astronomical Observatory.- 3. Interstellar lines other than hydrogen.- 4. Interstellar molecular hydrogen (Abstract).- 5. General discussion.- B. Emission.- 1. The night sky brightness measured from satellites Kosmos 51 and 213.- 2. Mariner 5 measurements of ultraviolet emission from the Galaxy.- 3. The ultraviolet background (intergalactic gas, the Galaxy, and subcosmic rays).- 4. Lyman-? radiation from nebular objects.- Space and ground-based stellar spectrophotometry: a summary.