WHAT STARS BECOME SUPERNOVAE?Tinsley, B. M.
doi: 10.1086/129857pmid: N/A
This paper assembles a variety of empirical lines of evidence on the masses and stellar-population types of stars that trigger supernova (SN) explosions. The main theoretical motivations are to determine whether type I supernovae (SN I) can have massive precursors and whether there is an interval of stellar mass between the masses of precursors of pulsars and white dwarfs that is disrupted by carbon detonation. Statistics of stellar birthrates, SN, pulsars, and SN remnants in the Galaxy show that SN II (or all SN) could arise from stars with masses greater than about 12 to 49 solar masses. Several methods of estimating the masses of stars that become white dwarfs are consistent with a lower limit of about 5 solar masses, so carbon detonation may be avoided. Studies of the properties of galaxies in which SN occur, and their distributions within galaxies, support the usual views that SN I have low-mass precursors and SN II have massive precursors. The restriction of known SN II to Sc and Sb galaxies is shown to be statistically consistent with massive stars in other galaxies also dying as SN II. Possible implications of the peculiarities of some SN-producing galaxies are discussed.
SPECTRAL TYPES IN THE OPEN CLUSTER IC 4665.Abt, H. A.; Levato, H.
doi: 10.1086/129858pmid: N/A
Spectral types for 18 bright cluster members have been derived from spectra of several dispersions. Among the peculiar spectra are (1) two B6 Vp stars with enhanced C ii, (2) one Hg-Mn Ap star, (3) a shell star, and (4) a classical Am star. Key words: open clusters - peculiar stars - spectral classification
ON THE RATIO OF EXTINCTION TO REDDENING FOR INTERSTELLAR MATTER USING GALAXIES. I. A LIMIT ON THE NEUTRAL EXTINCTION FROM PHOTOMETRY OF THE 3C 129 GROUP.Sandage, A.
doi: 10.1086/129859pmid: N/A
The ratio of total extinction to reddening of interstellar matter has been determined by a method applied to galaxies in the highly obscured 3C 129 and 3C 129.1 group. The difference between the observed magnitude of the first-ranked group member and the magnitude calculated from the redshift-apparent magnitude diagram (at the known redshift of the group) is the total extinction to within the dispersion in magnitude that applies to the first-ranked cluster member. Comparison of the observed color with the known intrinsic color of giant E galaxies gives the color excess and, therefore, the ratio of total extinction to reddening. Photometry of the 3C 129 group gives a ratio of 3.72 plus or minus 0.32; correction for the finite bandwidth of the BV system gives a ratio (O-star base) of 3.35 plus or minus 0.29. Comparison with the ratio determined from the color-difference method gives a limit for the fraction of neutral-to-selective extinction which is a null result to within the statistics. Hence, no neutral extinction has been detected at the one-sigma level of the experiment. Use of the method on many additional groups of galaxies is expected to reduce the error of this limit substantially.
THE NIGHT SKY BRIGHTNESS AT MCDONALD OBSERVATORY.Kalinowski, J. K.; Roosen, R. G.; Brandt, J. C.
doi: 10.1086/129862pmid: N/A
Baseline observations of the night sky brightness in B and V are presented for McDonald Observatory. In agreement with earlier work by Elvey and Rudnick (1937) and Elvey (1943), significant night-to-night and same-night variations in sky brightness are found. Possible causes for these variations are discussed. The largest variation in sky brightness found during a single night is approximately a factor of two, a value which corresponds to a factor-of-four variation in airglow brightness. The data are used to comment on the accuracy of previously published surface photometry of M 81.
THE SPECTRAL ENERGY DISTRIBUTION OF NGC 1275.Shields, G. A.; Oke, J. B.
doi: 10.1086/129864pmid: N/A
An analysis of absolute spectral energy distributions for NGC 1275 (Per A) covering the wavelength interval from 3300 A to 10,800 A is presented. The data are consistent with the heavy reddening discovered by Wampler (1971). The H-alpha intensity varied by less than 10% between the times of Wampler's earlier measurements and the two occasions of the present observations. The line-emitting region has a characteristic density of about 10 to the 4.5 power per cu cm, a mass of about 10 to the 5.5 power solar masses, and a volume filling factor of about 10 to the -6th power. The gas may be ionized by shock waves or by nonthermal or stellar radiation. It is suggested, in the vein of Minkowski's (1957) original proposal, that the high-velocity emission-line knots described by Minkowski are H II regions in a Perseus-cluster galaxy or intergalactic gas cloud seen in projection against NGC 1275.
SPECTROSCOPY OF FIVE FAINT M DWARF STARS NEAR THE NORTH GALACTIC POLE.Koo, D. C.; Kron, R. G.
doi: 10.1086/129865pmid: N/A
Radial velocities and estimates of absolute magnitudes are presented for five M dwarfs selected from a proper-motion study of M stars near the north galactic pole by Murray and Sanduleak (1972). The derived mean distance and velocity dispersion are significantly larger than the corresponding quantities found by Murray and Sanduleak, but only a small sample limited to the earlier-type stars on their list was used in the present study.