Publications of the Astronomical Society of the Pacific

Langer, G. E.; Kraft, R. P.; Carbon, D. F.; Friel, E.; Oke, J. B.

doi: 10.1086/131781pmid: N/A

The authors find that >[C/Fe]< ≈ 0.0 in stars at the base of the subgiant branch and approaches +0.1 in stars near the main-sequence turnoff in the metal-poor globular cluster M92. The carbon abundance falls on the average by about 0.5 dex by the time stars reach MV0 ≡ +1.5. These carbon depletions occur early enough and are approximately the right size to account for the large average nitrogen enhancement ([N/Fe] ≡ +0.65) observed in M92 subgiants near MV0 ≡ +1.5. Although the present observations do not absolutely prove that C→N conversion and mixing alone control the C- and N-abundances seen in M92 giants, neither is there any longer a compelling reason to believe there were large primordial nitrogen abundance variations in M92. The mechanism responsible for the large (Δ[C/Fe] ≈ 1.0) carbon depletions observed as stars ascend the M92 giant branch to the red-giant tip remains unknown.

Peterson, C. J.

doi: 10.1086/131782pmid: N/A

Photometric data for 78 elliptical galaxies observed in V and B colors with the Cerro Tololo Inter-American Observatory 0.9-m telescope during April and November 1983 are examined. Lamberts' data from the ESO survey of the ESO (B) Atlas are presented. The data are analyzed in order to study the motion of the Local Group and the spatial distribution of galaxies in the local region of the universe. The photometric data are compared to the data in the photometry catalog of Longo and de Vaucouleurs (1983, 1985) and good correlation between the observations is detected.

Gutierrez-Moreno, A.; Moreno, H.; Cortes, G.

doi: 10.1086/131783pmid: N/A

Electron temperatures and densities for 14 bright southern planetary nebulae, obtained from data previously published, are presented here. It is found that the difference between the logarithmic electron densities obtained from the ratio of nebular lines and from the ratio of auroral or transauroral lines to nebular lines is linearly correlated with the electron densities. It is also found that the ratio of the temperatures in the O III and N II forbidden line regions, TH/TL, is linearly correlated with the degree of excitation, measured through the intensity of He II 4686A. The relation is double valued, with values of TH/TL both larger and smaller than 1 for the same degree of excitation. Up to this moment, no physical parameter giving a unique correlation with TH/TL has been found.

Gray, D. F.; Toner, C. G.

doi: 10.1086/131784pmid: N/A

The authors observed a group of supergiants spanning the F5 Ib to K2 Ib interval. The line asymmetries of the F supergiants are found to be large and opposite in direction from the normal case seen in cooler and less-luminous stars, and in the Sun. There is a continuous and monotonic change in the bisector behavior with spectral type, with the transition from the anomalous to the normal asymmetry occurring near G1 Ib. The authors reproduce the observations with numerical simulations based on a simple two-stream model, and from this deduce velocities of rise of the hot material to be ≡ -25 km s-1 for the F Ib supergiants.

Sadun, A. C.; Ressler, M.

doi: 10.1086/131785pmid: N/A

Photometric observations were made during the summer of 1984 of the short-period dwarf Cepheid XX Cyg. The light curves of XX Cyg taken with B and V filters are presented, as well as current estimates of various parameters inferred from them. Among these parameters are an accurate determination of the period and the change in visual light output. In addition, the light curves suggest a small migrating bump that slowly changes in shape and position over many periods, and may even disappear altogether.

Hutchings, J. B.; Thomas, B.; Link, R.

doi: 10.1086/131786pmid: N/A

Measurements have been made on about 50 spectra of TT Ari taken during high states in 1979 and 1981. The phasing of the velocity variation T0 appears to be the same for all high-state spectra, and varies smoothly with mean system magnitude in lower states. The emission-line equivalent widths and their orbital phase dependence do not appear to be related only to system state. There is normally an orbital modulation of line equivalent widths when the system is bright, but its phasing is variable. The velocity amplitude in high state appears to be variable by at least a factor two.

RaoVahia, A.R.M.N.

doi: 10.1086/131787pmid: N/A

In continuation of a recent study of Abt (1984b) that multiple author papers get higher citations, it is suggested that this may be due to a higher circulation of the preprints/reprints of the publication as well as higher frequency of contact of the authors with the other scientists in the same field. This suggestion is further supported by our earlier study (Rao and Vahia 1984) that joint-author papers tend to be written by comparatively senior scientists who are definitely well established and consequently extensively read.

Rossano, G. S.

doi: 10.1086/131788pmid: N/A

A small, versatile microcomputer-based data-acquisition system has been developed for astronomical observing in the infrared. The hardware is a 16-bit 8086/8087 based system which has been tailored for use in spectroscopic observing programs. The hardware is operated using interactive software which permits high-speed data acquisition and real-time analysis of spectroscopic data. The combined hardware and software system facilitates flexible, efficient, and uniform operation of a variety of spectroscopic instruments. Key words: microcomputers-spectroscopic instruments

Tollefson, M. V.; Bloomer, R. H.

doi: 10.1086/131789pmid: N/A

The addition of an auxiliary circuit to the Heathkit GC-1000 clock is described. The circuit, which consists of two integrated circuits, two resistors, and three capacitors, will supply a more accurate timing pulse to the computer. The circuit contains two input signals and produces one output; the inputs are multiplexed seven-digit displays (two digits for hour, minute, and second, and one for tenths of a second) and the output appears as a string of about 10 low-going pulses about 1.25 ms in duration. Low pass filters (R1 and C1) are utilized to eliminate extraneous pulses. The materials and procedures for attaching the circuit to the clock are examined. The software for the data set ready signal, and the method for accurate timing of data collection are discussed. The accuracy of the clock is evaluated and it is observed that the circuit improves the correct time provided by the clock from + or - 29 ms to + or - 5 ms.