Publications of the Astronomical Society of the Pacific

Morbey, C. L.; McClure, R. D.

doi: 10.1086/131504pmid: N/A

Recently obtained CCD photographs of the giant elliptical galaxy NGC 3557 were examined in order to determine its luminosity structure and to discern whether the galaxy possesses a globular cluster system. A 50-minute frame was obtained from the CCD camera of the 4-meter telescope of the Cerro Tololo Inter-American Observatory by averaging ten different 300-second exposures. The frame shows that the luminosity structure of NGC 3557 was very much like the structures of first-ranked galaxies in poor clusters. An extended luminous envelope surrounds the galaxy, but it is less luminous than the envelope of a cD galaxy in a rich cluster. Only a marginal excess of faint star-like images brighter than the limiting magnitude of 25.5 mB could be detected. It is suggested that a sparse globular cluster population with a specific frequency of 0.8 + or - 0.6 S is located in NGC 3557.

Corso, G. J.; Schultz, J.; Purcell, B.; Garino, G.; Dey, A.

doi: 10.1086/131505pmid: N/A

The results of photometric observations of 3C 273 carried out in blue light with a 1-meter reflecting telescope are reported. The results were obtained using a standard 103a-O and GG 13 plate-filter combination, and data reduction was performed using a Cuffey Iris photometer. The internal accuracy of the blue magnitudes is estimated to be 0.05 mag. The complete data are given in a table.

Reed, B. C.

doi: 10.1086/131506pmid: N/A

Using the data homogenization technique of Reed and FitzGerald (1982), some 1400 photoelectric observations of integrated UBVRI colors for 114 galactic globular clusters have been reduced to the UBV and VRI systems of van den Bergh (1967) and Hamuy (1984), respectively. Use is made of all mutually common obervations.

Stocke, J.; Silva, D.; Black, J. H.; Kodaira, K.

doi: 10.1086/131507pmid: N/A

High-resolution spectral observations of the optical candidate for the X-ray transient X0331 + 53 are presented. The data show broad hydrogen and helium emission and strong interstellar absorption corresponding to a visual extinction of about 7 mag. No photospheric absorption in the emission lines, and no radial-velocity variations greater than 0.5 km/s were found over a three-day period. It is concluded that the optical continuum does not arise at or near the primary star. As an example of the spectrographic data, a resolution profile of H-alpha emission in X0331 + 53 is provided.

Mould, J. R.; Schneider, D. P.; Gordon, G. A.; Aaronson, M.; Liebert, J. W.

doi: 10.1086/131508pmid: N/A

Nine carbon stars at high galactic latitude, including the first eight carbon stars from the Case survey have a corrected line-of-sight velocity dispersion of 101 km s-1. If they are similar to the carbon stars found in dwarf spheroidal galaxies, they range in distance from 5 to 50 kpc. Their velocity dispersion is higher than the prediction of the cylindrical model for the galactic velocity ellipsoid by Ratnatunga and Freeman, but equal to that of galactic globular clusters. One of these stars may have an age of less than six billion years.

Dobias, J. J.; Plavec, M. J.

doi: 10.1086/131509pmid: N/A

Recent optical and ultraviolet observations of U Sge are presented, and the results are compared with observations of U Cephei. The observations were carried out with: the International Ultraviolet Explorer (IUE) satellite; with the ITS scanner of the Lick Observatory; and with a Varo image-tube camera attached to a coude spectrograph. Comparison with data for U Ceph showed that U Sge is of the B7.5 V spectral type with an effective temperature of 12,250 + or 250 K, and a surface gravity of 3.9 + or - 0.1 log g. The secondary component of U Sge appears to be of the G4 III-IV spectral type. The best estimate for the distance of U Sge was 295 + or - 20 pc. Emission lines of the W Serpentis type were found in the IUE spectrum for U Sge. Although the observed fluxes for the lines were low, the powers were half as strong as those observed in U Cep. Selected emission lines of Fe II, Si II, and Si III were also found assuming solar abundances. A complete summary of the IUE and optical data is provided in a series of graphs and tables.

Mochnacki, S. W.; Starkman, G.

doi: 10.1086/131510pmid: N/A

The spectrum of RT Ser (Nova Serpentis 1909) was observed in 1979 in the range 6300 Å to 6750 Å, at a resolution of 0.6 Å. In addition to the dominant Hα line, weak emission lines of [O I] λ6363 and He I λ6678 were detected. These lines have radial velocities of 64, 82, and 77 km s-1, respectively. Emitting regions with different physical conditions around RT Ser appear to have different radial velocities.

Joner, M. D.; Johnson, S. B.

doi: 10.1086/131511pmid: N/A

Photometric observations have been carried out over ninety percent of the pulsation cycle for the variable star HD 200925. The observations were obtained using a single-channel photometer, and a photomultiplier attached to a 61-cm reflecting telescope. The instrumental indices were reduced to the standard Stromgren and beta-systems of 13 standard stars. The photometric data show that HD 200925 is multiperiodic. A reddening value of 0.040 mag was derived as the average of the variable and comparison star observations. Analysis of the intrinsic (b-y) and cl values for one primary pulsation cycle indicated a mean effective temperature of 7470 K, and a mean surface gravity of 3.87 log g. HD 200925 is found to have a somewhat higher (+0.33) Fe/H abundance ratio than stars in the Hyades. The observed magnitude and color variations of HD 200925 are reproduced in graphic form.