Publications of the Astronomical Society of the Pacific

Canterna, R.; Crawford, D. L.; Perry, C. L.

doi: 10.1086/130482pmid: N/A

Multicolor uvby and H-beta photometries have been obtained for 42 stars in the field of the galactic cluster NGC 1039 (M34). Analyses give a mean cluster reddening of E(B-V) = 0.07 m and a distance modulus of 8.2 m corresponds to a distance of 440 pc. The metallicity of NGC 1039 is similar to the Pleiades cluster; its age is intermediate, older than the Pleiades but younger than the Hyades cluster. The properties of its three Ap stars, two additional peculiar stars, membership criteria, and gaps in the UBV color-color relation are discussed

Kenyon, S.; Starrfield, S.

doi: 10.1086/130483pmid: N/A

Polytropic models are constructed for Bok globules, and the calculated density distributions are used to obtain theoretical curves of Aupsilon versus radius. These curves, when compared with observations, will provide the density structure and the temperature required to prevent collapse for the globules. Also used are published values of Aupsilon versus radius for B361 and Coalsack globule 2 and it is found that B361 resembles an n = 1.75 polytrope while globule 2 resembles an n = 2.5 polytrope. Therefore, at densities of about 100,000/cu cm these two globules are centrally condensed. It can also be predicted that if their measured temperatures turn out to be no greater than about 12 K, then they are already collapsing.

Sabbadin, F.; Bianchini, A.

doi: 10.1086/130484pmid: N/A

The spectrum of the planetary nebula M4-18 (146+7°1, Perek and Kohoutek 1967) consists of broad emission lines of C II, C III and C IV of the central star superimposed on the emission lines of H I, [N II], and [S II] of the nebula. The [O III] emission lines λλ4959-5007 are very weak, a rather atypical case among planetary nebulae. The similarity of M4-18 to BD +30°3639 (Campbell's star) is discussed.

Sabbadin, F.; Bianchini, A.

doi: 10.1086/130485pmid: N/A

Spectroscopic investigations of M1-76 indicate that it is not a planetary nebula, but can be classified among the BQ [] stars.

Sabbadin, F.; Bianchini, A.

doi: 10.1086/130486pmid: N/A

Two hundred and fifty-two H II regions have been identified in NGC 4449 and positions in rectangular coordinates are given. The size-frequency relation is compared with that of M33, NGC 2403, NGC 628, NGC 3631, and NGC 6822. Very sharp and faint filaments radially arranged with respect to the main body of the galaxy have been identified. The characteristics of the discrete radio source recently detected by Seaquist and Bignell (1978) are discussed.

Barnes, T. G.; Moffett, T. J.

doi: 10.1086/130487pmid: N/A

An equatorial-extinction star network, based on 1503 observations of 37 stars, is presented. These results together with those of Crawford et al. (1971) provide a well-determined UBVRI extinction network. Identification charts are included.

Gutierrez-Moreno, A.

doi: 10.1086/130488pmid: N/A

A simple method for computing intrinsic color indices for stars of all luminosity classes applying the Q-method is presented. Calculations are performed on supergiants, less-luminous supergiants, giants and dwarfs, noting some systematic errors. The two main systematic errors were: (1) those produced by errors resulting from the color-color relations and (2) those caused by assuming a wrong value of x (first order coefficient in the color excess ratio). All of these errors were found to be dependent on the amount of reddening, the luminosity class, and the value of x itself. The errors due to the fitting of straight lines to the color-color relations were found to be independent of the amount of reddening and were generally small, reaching at most a 0.02 magnitude.

Batten, A. H.; Morbey, C. L.; Fekel, F. C.; Tomkin, J.

doi: 10.1086/130489pmid: N/A

High-dispersion spectrograms of the triple system HD 165590 are examined which were obtained during the periastron passage of 1978. The orbital elements are determined by combining the spectroscopic observations with visual observations of the long-period pair. The elements determined include a period of 20.25 yr, an orbital inclination of 82.7 deg, an eccentricity of 0.958, a semimajor axis of 151 billion km, and a longitude of the ascending node of 271.9 deg. A total system mass of 2.51 solar masses and a parallax of 0.024 arcsec are deduced. Reticon observations are discussed which indicate that the short-period binary (0.88-day period) is the visual primary. The spectra of the brighter component of the short-period pair and the visual secondary are shown to be visible in the combined light and to be of approximate types G0 and G5, respectively.