Some characteristics of the spectra of F-, G-, and K-type stars.

Abstract

view Abstract Citations (3) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Some characteristics of the spectra of F-, G-, and K-type stars. Roman, Nancy G. Abstract At the Yerkes Observatory at the present time we are engaged in an extension of the Morgan-Keenan-Keilman system of spectral classification to all northern stars brighter than 5.5 visual magnitude. Although the work has not been completed, two results seem worthy of attention. Among the 168 stars studied having HD spectral types F~ to G~, there are 13 F~ giants, 29 G8 giants, 13 Ko giants, and only 12 giants of types F6, F8, Go, G2, and G5. That the scarcity of early G-type giants is real is shown clearly by a plot of colors against absolute magnitudes. Fourteen of the stars show a composite spectrum, usually consisting of a late-type giant and an A- or F-type star. Those with an A-type component are easily recognized by the characteristic appearance of the K-line but those with an F-type component simulate the spectra of normal early G-type giants. Capella, composed of an F6 star and a late G giant, is an excellent example of the latter type of system. The resulting composite spectrum can be distinguished from that of a G2 giant on low dispersion primarily by the strength of the CX. Since late- type giants are numerous and early G-type giants are scarce, a large percentage of the stars classed as early G-type giants are probably binaries with composite spectra. A number of giant and dwarf stars of types F~ to G~ show systematically weaker lines than other stars in the same position on the H-R diagram. Space velocities based on spectroscopic parallaxes and corrected for a solar motion of 20 km/sec were computed for 8~ stars of types F~ to G5. It was found that the speeds of the stars with strong lines show a maximum frequency between 10 and 20 km/sec with no stars having speeds larger than 70 km/sec. On the contrary, the speeds of the 40 stars with weaker lines show only a broad maximum between 30 and 6o km/sec; 8 of these stars have speeds greater than 70 km/sec. Verkes Observatory, Williams Bay, Wis. Publication: The Astronomical Journal Pub Date: October 1950 DOI: 10.1086/106403 Bibcode: 1950AJ.....55..182R full text sources ADS |