International Business Machines for spectroscopic absolute-magnitude reductions and results for 500 A5-G stars.

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view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS International Business Machines for spectroscopic absolute-magnitude reductions and results for 500 A5-G stars. Hoffleit, Dorrit Abstract In resumption of the war-interrupted Harvard program for the determination of spectroscopic absolute magnitudes of bright southern stars, provisional results have now been obtained for approximately 500 A5-G2 stars, most of them 5-7 visual mag. and south of 200. The spectra were obtained at the Harvard Southern Station with the I ~-inch Boyden refractor and an ob- jective prism giving a dispersion at H~ of 45 A!mm. The estimates of line intensiti~s were carried out at Harvard, two-thirds of them prior to 1942. The reductions were performed on the International Business Machine equipment of the Ballistic Research Laboratories, Aberdeen Proving Ground, through the generous perm1s- sion of Col~nel Leslie E. Simon. The advantages of punch cards in the reduction of data for "normal" stars are discussed. The spectroscopic absolute magnitudes are compared with absolute magnitudes computed from trigonometric parallaxes, reduced proper motions, and spectroscopic results obtained at other observatories. The relative scale and zero- point errors of the Harvard reductions for the main sequence stars are within the natural uncertainties of the various systems. A total dispersion in absolute magnitude of +0.7-0.8 is found of which +0.5 mag. is apparent observational error. This leaves +0.5 mag. as the indicated dispersion of the true absolute magnitudes, a result not inconsistent with published results from various statistical investigations. The list of stars contains numerous peculiar objects, namely: 6 "Strontium stars" I "Chromium Europium star" 39 "Metallic-line stars" 9 Cepheid variables I Star with probable variable spectrum, HR 7055 23 Other supergiants. The Harvard absolute magnitudes for the supergiant stars are poorly determined. This is primarily because these stars were not separated from the others in the automatic machine reductions, and it is well known that all the criteria for the run of the stars are not applicable to supergiants. Also, too few data are available for an independent calibration of the supergiants. They are, however, included in the discussion in order to demonstrate the consequence of ignoring luminosity class before `calibrating supergiant luminosities. About 40 of the stars have "ambiguous" spectral classes. On the basis of Miss Cannon S Henry Draper criteria they are A stars while Mount Wilson's metallic-line criteria place them in the F groups. The absolute magnitudes estimated for both types indicate no definitive preference for either. Color data (Cape photographic magnitudes) indicate a slight preference for the F-types. On the other hand, in a comparison of Victoria (classified on the Draper system) and Mount Wilson spectral classes for northern stars, the colors of stars with discordant spectral classes appear to favor the earlier class. For 50 of the stars the Yale Bright Star Catalogue has listed variable radial velocities: 7 Cepheids, 17 possible binary stars, the rest undefined. For 30 of these more than one Harvard spectrum each was available. With the exception of the plates for one Cepheid, the plates showed no variations in line intensities beyond the differences attributable to diverse quality and exposure. The reduction and analysis of data such as those described require a large amount of sorting, listing, averaging and re-sorting of data. A moderately experienced operator would find I.B.M. equipment advantageous except in the analysis of those peculiar stars which are not, amenable to statistical methods. Harvard College Observatory, Cambridge, Mass. Publication: The Astronomical Journal Pub Date: 1948 DOI: 10.1086/106169 Bibcode: 1948AJ.....54S..39H full text sources ADS |