Otto Struve

THE PROBLEM OF U CEPHEI

The eclipsing binary U Cephei consists of a small, hot, and massive primary and a large, cool, and less massive secondary. The orbital period of nearly 2.5 days is subject to small irregular changes. A discussion of these changes by D. Wood will be published separately. The photometric orbital elements were determined in 1956 by Bolokadze1 by means of photographic determinations of the brightness of the system by Chudovichev,2 whose own discussion is now somewhat out of date.

SPECTROGRAPHIC OBSERVATIONS OF ALGOL

According to the elemeni determined by Pavel, the middle of the principal eclipse of Algol1 should have occurred at 6h 03m UT on September 21, 1956.2 On this night Sahade obtained a series of spectrograms of Algol with the coude spectrograph of the 100-inch telescope of the Mount Wilson Observatory. The dispersion was about 4 . S Â/mm in the violet and blue regions and about 9 A/mm at Ha. The first spectrogram, at 6h 04m UT, had an exposure of 75m and represents, as nearly as can be ascertained from the available literature, the precise time of the photometric minimum. Plate I shows the conspicuous doubling of the line Mg n 1 4481 a phenomenon discovered by Morgan in 19353 and most recently discussed by Struve.4 Algol is a multiple system : components A and B revolve with a period of 2 . 87 days ; component C has a period of 1 . 87 years. Component A is bright, and its spectral type is B8 ; B is invisible in the photographic region; but C produces a large number of narrow metallic lines, mostly of Fe i, which may to some extent blend with very weak, but relatively broad, lines of A. The lines of Fe ii are certainly to a large extent produced in the atmosphere of star A.

THE SPECTRUM OF BETA AURIGAE

THE SPECTRUM OF BETA AURIGAE (Abstract) Otto Struve and Clare Driscoll Berkeley Astronomical Department, University of California Figures 1 and 2 show the profiles of the lines CanK and ili<7 ii 4481 on twelve Mount Wilson coude spectrograms (dispersion 3 A/mm) . In each profile the red component is plotted on the left-hand side. The phases were computed with the formula used by B. Smith.1 At phase zero the less massive component is eclipsed. As was already shown by R. M. Petrie, the more massive

THE 140-FOOT RADIO TELESCOPE OF THE NATIONAL RADIO ASTRONOMY OBSERVATORY

The 140-foot radio telescope will be a precision instrument that will be used for the measurement of accurate positions of small radio sources, for making accurate maps of larger sources, for the determination of the radiative fluxes of many sources at different frequencies, for the study of variable sources of several kinds, for the measurement of the refraction and scintillation of radio waves, etc. Experience with other instruments has demonstrated the need for a fairly large and exceptionally stable telescope that will remain in use and retain its characteristics over intervals of many years. In optical astronomy the most accurate measurements of stellar coordinates have been obtained through the use of large transit instruments that have remained essentially unchanged for several decades. It would be an exaggeration to suggest that the 140-foot telescope will do for radio astronomy what modern meridian circles are doing for optical astronomy, but it should perform considerably better than Ulug-Begs or Tycho Brahes large visual quadrants. It would also be unrealistic to expect the 140-foot telescope to compete in photometry with present-day photoelectric

SPECTROSCOPIC FEATURES OF Β LYRAE

1. In a recent paper the distortion of the radial-velocity curve of s Lyrae during the partial phases of the eclipse was shown to undergo significant changes in two successive cycles.1 On June 25, 1958 the radial velocities obtained from the Sin lines of the B8 star were found to be approximately 10 km/sec more positive than those obtained on July 8, 1958 in the same phase interval 0^04 to 0?06, counted from the epoch of mid-eclipse. There was only a very slight indication of a difference in the same sense between phases (Fll and 0?14 on June 26 and July 9 ; there was no systematic difference between the two cycles in the phase interval 0?95 to 0?99 on June 24 and July 7. The systematic difference observed in the interval 0?04 to 0?06 was thought to be correlated with a systematic difference in the light curve of the variable which suggested that the integrated brightness of s Lyrae was lower on June 25 than on July 8.2 There was also an indication of a strengthening of the strong absorption lines produced in the shell of s Lyrae when the integrated brightness of the star was reduced and when the distortion of the velocity curve was less pronounced. We have now re-examined the B8 radial velocities of s Lyrae during the phase interval 0?95 to 0?15 as obtained from spectrograms taken in 1955. 3 The velocities obtained from the Si n lines in cycles 4-5 (June 3 to 10, 1955) and in cycles 6-7 (July 4 to 11, 1955) show no systematic differences in the intervals 0?95 to 0?99 and 0?03 to 0?06, but do show significant systematic differences in the interval 0?ll to OH 5. The three phase intervals covered by the 1955 observations accidentally agree very closely with the three intervals previously discussed. Figure 1 shows the Si n radial velocities. The observations in cycle 6-7 are displaced by about +3 km/sec with respect to those of cycle 4-5. As was already previously known, the meas-

THE VAN HOOF EFFECT IN BETA CANIS MAJORIS STARS

In 1953, A. van Hoof1 discovered a remarkable time lag in the radial velocities of β Canis Majoris determined from the hydrogen absorption lines with respect to the radial velocities determined from the rest of the absorption lines. He later2 found the same effect to be present in 16 Lacertae another member of the β Canis Majoris group of pulsating stars. The character of the lag envisioned by him is illustrated at the top of Figure 1. The velocity curve remains the same in shape and is simply displaced by about 0 . 04P with respect to the velocity curve defined by the lines of He ι, Ο π, Si in, etc. The phenomenon was therefore believed to resemble that known to exist in ordinary Cepheid variables.

Notes on Stellar Spectra.

Phi Persei. This star has a well-known helium-shell spectrum, with He i 3965 sharp, while those lines which have nonmetastable lower levels are usually broad and shallow. The H lines show absorption cores between broad emission wings. Several spectrograms, obtained on October 22, 1951, with the coude spectrograph of the Mount Wilson 100-inch telescope show that He i 3888 and He i 3188 (23S n3P°) also have strong absorption cores. But while the //-cores are distinctly unsymmetrical, or even double, being shaded shortward, the He cores are nearly symmetrical. Especially interesting is an exceedingly narrow, deep, absorption line which is centrally superposed over the normal absorption core of He i 3888. This feature has not been seen previously since it requires a dispersion of at least 10 A/mm. Its width is so small that it must come from an even higher layer than the rest of the He and H shell spectrum. Rotation, which at the normal shell level is sufficient to appreciably broaden the cores of many lines, is negligible at the height where the very narrow line originates. Moreover, turbulence at this high level is also negligible : it must be less than 2 or 3 km/sec, resembling in this respect the conditions within interstellar gas clouds. Since there is strong independent evidence that at more moderate heights, within extended stellar atmospheres, the turbulence at first increases with the height, we must now conclude that at still higher elevations it decreases. The H absorption cores are not very strong and can be seen as distinct, narrow lines only to H 14. Beyond this limit there are a few diffuse absorption features which probably result from the overlapping of broad underlying hydrogen lines. Even these disappear long before the Balmer limit is reached. AR Lacertae. The discovery of double absorption lines in the s Canis Ma joris stars, 12 Lacertae and o Scorpii, has led to

THE DECLINE OF INTERNATIONAL COOPERATION IN ASTRONOMY.

E. Kellogg, chief of the Soil Survey Division, Bureau of Chemistry and Soils, Department of Agriculture; Loyd V. Steere, agricultural attach6, . Berl in; L . G. -Michael, agricultural attachk, Belgrade; J. Clyde Marquis, American member of the Permanent Committee, International Institute of Agriculture, Rome; Dr. C. L. Stewart, professor of agricultural economics, University of Illinois, and Dr. John K. Galbraith, professor of economics a t Harvard University. Alan S. Rogers, secretary of embassy a t Rome, will be secretary of the delegation.