Publications of the Astronomical Society of the Pacific

Walker, Gordon A.; Walker, Andrew R.; Racine, Rene; Fletcher, Murray J.; McClure, Robert D.

doi: 10.1086/133385pmid: N/A

The ability of directly detect close, faint companions to bright stars, depends on image sharpness to a high power (6 to 8 in the case of a planet). We present the first observations with a cornographic mode of the high-resolution camera on the CFH 3.6-m telescope. About 98% of the light of the guide star fell through a 5 arcsec hole and the wings of the image were well-represented by a Moffat profile. Chopping in angle did not reduce glare in the wings as much as we expected because of eccentricity of the star in the aperture, residual asymmetry in the point spread function, and weak radial patterns (in addition to those from the spider). Combing an angular chop with the image of another star to give an instrumental psf, was more successful. We discuss the recognition and photometry of a faint star in the field of sigma Dra. Snapshots of Procyon yielded a separation of 5.2 arcsec, mv = 11.3, B-V = +0.26, and B-I = +0.62 for its white dwarf companion. The detection limits close to sigma Dra, tau Cet and epsilon Eri, are still some 5 magnitudes too bright for the detection of giant planets. Nonetheless, we remain optimistic that, with improving centering, the introduction of frame transfer CCDs, longer exposure times in the 15 percentile seeing at CFHT, and the use of other stars to define the telescope psf and fixed speckle background, it may be possible to realize these limits. Alt-azimuth telescopes present a special challenge!.

Heintz, Wulff D.; Cantor, Bruce A.

doi: 10.1086/133386pmid: N/A

Completion of long-term astrometric plate series yields revised results on the orbits and parallaxes. The subdwarf mu Cas seems to be overluminous; the distance of the supergiant epsilon Aur is near 600 pc. The unresolved companion in the red dwarf pair BD +6degree398 is of very low mass, and the companion of BD +67degree552 massive but probably underluminous.

Tomkin, Jocelyn; Lambert, David L.

doi: 10.1086/133387pmid: N/A

We report observations of visual and near-infrared C I, N I, and O I lines in the A2 II secondary of V356 Sgr made during a total eclipse of the primary. We confirm the weakness of the secondary's C I lines first seen in ultraviolet observations. Based on a marginal detection of the 9100A C I lines we estimate that relative to a standard star (HR 7145; A0 II) of similar spectral type the [C/Fe] abundance ratio of the secondary is -1.7 ± 0.3 dex. The secondary is not significantly underabundant in N or O. We interpret the C poorness of the secondary as a result of mass transfer, which has removed its outer layers and exposed its CN-processed interior.

Fox, G. K.

doi: 10.1086/133388pmid: N/A

The behavior of hte B-band polarimetric data of Y Cyg (Koch and Pfeiffer 1989) are analyzed. A period search of the data indicates that the only significant periods arise due to the frequency with which the system had been observed. Around the eclipsing phases there is evidence to suggest that the primary star possesses a stellar wind. The speculations by Koch and Pfeiffer regarding the possible envelope geometry are also commented upon.

Giovagnoli, Alessandra; Mould, Jeremy

doi: 10.1086/133389pmid: N/A

Spectrophotometry of 36 Long Period Variable stars in M33 is presented. Most of them show strong TiO bands. These spectra together with published photometry indicate that the red variables exceeding 5 x 104 L are M supergiants, evolved from young massive stars which are prominent in this galaxy. A small number of lower luminosity stars are present in this sample. These are asymptotic giant branch stars. We identify 2 of them as carbon stars. There are no strong S stars.

Danks, Anthony C.; Dennefeld, Michel

doi: 10.1086/133390pmid: N/A

An atlas of stellar spectra covering the wavelength range from 5800A to 10,200A is presented of 126 southern MK standard stars, covering the luminosity classes I, III, and V. Some peculiar stars are included for comparison purposes. The spectra were obtained at a resolution of 4.3A per pixel using a Cassegrain mounted Boller and Chivens spectrograph equipped with a Reticon detector. The quality and utility of the data are discussed and examples of the spectra are presented. The atlas is available in digital format through the NSSDC.

Crawford, David L.

doi: 10.1086/133391pmid: N/A

New uvby and Beta photoelectric photometry has been obtained for stars in NGC 1502, a young open cluster with relatively high interstellar reddening. It is shown that some of the previous published data for the cluster suffers from small systematic errors. After correction for zero-point differences, the previous data have been combined with the new data and accurate values of the interstellar reddening [E(b-y)=0.54 mag] and distance modulus [(V0-MV=9.71 mag] have been obtained. These are compared with similar values calculated from published UBV photometry and MK spectral types, which agree well with the uvby-Beta analysis. It is found that the reddening is not variable over the cluster field, contrary to previous estimates. The fact that systematic errors exist in precise photometry highlights the importance of a careful selection of standard stars in any photometry of reddened B-type stars.

Sarajedini, Ata

doi: 10.1086/133392pmid: N/A

The first CCD color-magnitude diagram (CMD) in B and V is presented for the Galactic globular cluster NGC 6535. From this CMD, which extends below the main sequence turnoff, we draw the following conclusions: (1) The horizontal branch (HB) is predominantly blue in nature with no RR Lyrae variables known to be cluster members. Nonetheless, based on a comparison with clusters which have blue HBs and RR Lyraes (M15 and M79), we infer a mean HB magnitude of < VRR ≥ 15.73 ± 0.11 for NGC 6535. (2) Again, via a direct comparison with the blue HBs of M15 and M79, we derive a cluster reddening of E(B-V)=0.44 ± 0.02. (3) When combined with the apparent color of the red giant branch at the level of the HB, (B-V)g = 1.18 ± 0.02, the derived reddening yields a metal abundance of [Fe/H] = -1.85 ± 0.10, similar to that of NGC 6397. (4) Application of the delta-VTO-HB and delta(B-V)SGB-TO cluster dating techniques reveals no perceptible age difference between NGC 6535 and NGC 6397. (5) A significant population of 9 blue straggler candidates is detected in NGC 6535. However, this is too few to facilitate a meaningful analysis of their radial distribution.