Simultaneous Photometry and Spectroscopy of the B2/E Variable Star HD45677

in IAU Colloq. 46: Changing Trends in Variable Star Research (1979)

Not Available

Line profiles in expanding envelopes

in Astronomy and Astrophysics (1979), 73

An attempt is made to show how the physical and geometrical parameters prevailing in an expanding stellar envelope can be inferred from an analysis of one or more observed line profiles. Attention is ... [more ▼]

An attempt is made to show how the physical and geometrical parameters prevailing in an expanding stellar envelope can be inferred from an analysis of one or more observed line profiles. Attention is given to the Sobolev approximation, line formation in outwardly accelerating envelopes, effects of a stellar core, and radiative transfer in outwardly decelerating envelopes. General equations are derived for both types of envelope, and some typical solutions are presented. Application of the method to P Cygni lines is discussed. [less ▲]

Photometric observations of 1978CA and 1978DA

in The Messenger (1978), 13

UBV photometric observations of the earth-crossing asteroid 1978 CA and the Mars-crosser 1978 DA are reported. Light curves are plotted which indicate that 1978 CA has a rotation period of approximately 3 ... [more ▼]

UBV photometric observations of the earth-crossing asteroid 1978 CA and the Mars-crosser 1978 DA are reported. Light curves are plotted which indicate that 1978 CA has a rotation period of approximately 3 hr 45 min and that 1978 DA rotates about its axis much more slowly than 1978 CA. The following color indices are determined: (B-V) of approximately 0.90 and (U-B) of about 0.48 for 1978 CA and (B-V) = 0.83 and (U-B) = 0.41 for 1978 DA. A model that may explain the observed smooth and nearly symmetric light curve of 1978 CA is briefly discussed. [less ▲]

Positions of the minor planets obtained in 1976 with the great objective prism of 40 CM /f equals 4 m/ of the ESO observatory at La Silla

in Astronomy and Astrophysics. Supplement Series (1978), 32

The results are presented of photographic observations of asteroid positions made in August 1976 at La Silla, Chile. The quality of the sky characteristics made it possible to record objects with the ... [more ▼]

The results are presented of photographic observations of asteroid positions made in August 1976 at La Silla, Chile. The quality of the sky characteristics made it possible to record objects with the magnitude 17. Measurements of all plates were conducted with the aid of the Ascorecord measuring machine of the Royal Belgian Observatory. The reduction method employed is based on the use of five reference stars. The equatorial planet coordinates can be easily obtained from the employed parameters with the aid of the formulas considered by Smart (1944). In the evaluation procedures use was made of the SAO catalog which had been recorded on magnetic tape by the Strasbourg Observatory. Three new asteroids were discovered. The obtained data are presented in two tables. [less ▲]

4U 1700-37

in IAU Astronomical Telegram N° 3290 (1978)

IAUC 3290 available at Central Bureau for Astronomical Telegrams.

Observations photographiques de la comète P/d'Arrest effectuées en 1976 à l'équatorial GPO de 40 cm de l'Observatoire Austral Européen (ESO) à La Silla (Chili).

in Bulletin de l'Observatoire Royal Astronomique de Belgique (1978), 9

Not Available

Radiative forces in expanding envelopes

in Astronomy and Astrophysics (1978), 62

The escape probability method introduced by Sobolev (1957) is applied to derive expressions for the radiative forces acting on atoms by the resonance scattering of radiation in envelopes which expand ... [more ▼]

The escape probability method introduced by Sobolev (1957) is applied to derive expressions for the radiative forces acting on atoms by the resonance scattering of radiation in envelopes which expand spherically with positive or negative radial-velocity gradients. In the latter case, it is shown that the contribution of the whole stellar envelope to the radiative force acting on individual atoms has the same effect as the one due to the stellar core radiation; i.e., a radial outward acceleration. Numerical applications to a two-level atom model illustrate the behavior of radiative forces in outward-accelerating and outward-decelerating stellar envelopes. [less ▲]

Spectroscopic and photometric observations of galaxies from the ESO/Uppsala list Second catalogue

in Astronomy and Astrophysics. Supplement Series (1978), 33

Abstract image available at: http://esoads.eso.org/abs/1978A&AS...33..243B

1978CA and 1978DA

in IAU Astronomical Telegram Nø 3185 (1978)

Orientation and structure of different components in the tail of comet West /1975n/

in Astronomy and Astrophysics (1977), 57

The orientation and structure of various components in the tail of comet West are studied from plates obtained March 4-11, 1976, with a 60-cm Schmidt telescope. A wavelike structure appears on March 10 ... [more ▼]

The orientation and structure of various components in the tail of comet West are studied from plates obtained March 4-11, 1976, with a 60-cm Schmidt telescope. A wavelike structure appears on March 10 and 11 in the type I tail. The mechanism for these waves is very probably excitation of surface waves in the ion tail due to Kelvin-Helmholtz instability at the interface between the comet plasma and the solar wind. According to this model, the measured wavelengths increase with distance from the comet head. The average wavelength of observed waves is 0.009 plus or - 0.002 AU. [less ▲]