G. Cortes

STUDIES OF SOUTHERN PLANETARY NEBULAE. I. FLUXES FROM BRIGHT PLANETARY NEBULAE.

A study of spectrophotometric observations of some southern planetary nebulae, made during 1980 and 1981, to increase and improve the absolute data for some of them and to detect objects of special interest, is discussed. Observed H-beta fluxes, logarithmic reddening correctitons, and intrinsic forbidden-line intensities relative to H-beta are given for 14 bright southern planetary nebulae. The results of the study, as well as those obtained from other authors, are listed in tables and compared.

A STUDY OF ATMOSPHERIC EXTINCTION AT CERRO TOLOLO INTER-AMERICAN OBSERVATORY. II

The behavior of the atmospheric extinction at CTIO during 1984 is analyzed. Rayleigh scattering, aerosol extinction, and ozone absorption parameters are determined. The behavior of the extinction during different months of the year is discussed.

SPECTROSCOPIC OBSERVATIONS OF THE PLANETARY NEBULAE ME 2-1

Observations of the planetary nebula Me2-1 were obtained with different set-ups, in order to analyze some effects of contamination produced by the second order ultraviolet spectrum in the first order red, for wavelengths longer than approximately 6000 A. This contamination problem will be discussed elsewhere. Here we present the observations of Me2-1, which include a wide wavelength range, from about 3100 to 10200 A. A comparison with previous results is shown for the wavelength intervals in common. From these data, the most relevant nebular parameters are derived, using lines in the optical and near IR regions. Some parameters corresponding to the central star are also determined. The results are compared with previously obtained values.

STUDIES OF SOUTHERN PLANETARY NEBULAE. II. ELECTRON TEMPERATURES AND DENSITIES.

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.

OBSERVATIONS OF FIVE SUSPECTED SYMBIOTIC STARS

We present observations of five objects previously classified as suspected symbiotic stars: CD -36 8436, He 2-101, Sa 3-43, Th 4-4 and V3804 Sgr. We find that they are all symbiotic, and deduce some of their physical characteristics.

ATMOSPHERIC EXTINCTION IN THE (U-B) COLOR INDEX.

Various methods for obtaining the atmospheric extinction in the (U-B) color index taking into account the dependence of extinction coefficient on the intrinsic color index of the star are examined. Numerical integrations are performed to determine synthetic color indices for 32 stars of spectral classes O9 to M0 and luminosity classes I, III and V through 0, 1 and 2 air masses, resulting in three (u-b) color indices for each star. Photometric reduction of the color indices to the (U-B) color index was then performed by the classical method, by the method proposed by Gutierrez-Moreno et al. (1966) and various modifications of it, and by the method proposed by Moffat and Vogt (1977). Comparison with observations of 71 stars in the standard region E5, nine extinction standard stars and 25 Johnson standard stars in the UBV reveals that the reduction of (U-B) by the classical method gives internal errors between two and three times larger than those obtained for (B-V) and V, while the methods of Gutierrez-Moreno et al. and Moffat and Vogt provide greatly improved accuracy.

THREE TYPE I PLANETARY NEBULAE

Observations of three planetary nebulae (PNe) with [N II] lambda-6583 > H-alpha are presented. They are He 2-111, He 2-145, and He 2-152. He 2-111 has already been classified by several authors as a type I PN. It is concluded that He 2-145 and He 2-152 are both type I PNe. Physical parameters of the nebulae and the central stars are given. It is found that He 2-152 has an extremely high He contents. The luminosities of the central stars run from 340 L* for He 2-152 to 1090 L* for He 2-111. When using distance independent parameters for the determination of the luminosity, much higher values are obtained, running from 5200 L* for He 2-145 to 19800 L* for He 2-111.

Probable Type I Planetary Nebulae

During a program of observations of planetary nebulae (PN) made at CTIO in 1982 using the 1.5 m telescope equipped with a Cassegrain spectrograph and a Vidicon detector, and repeated in 1991 using the same configuration with a CCD detector, we found four PN for which Hα < [N II] λ6583: He2–109, He2–45, He2–152, and He2–163. The analysis of the data was made using the computing facilities of Cerro Tololo Computing Center at La Serena, and of the Centro de Procesamiento Digital de Imagenes of the Departamento de Astronomia de la Universidad de Chile.

Two Southern Low Excitation Planetary Nebulae

Within a spectroscopic study of some southern planetary nebulae, we have observed 32 objects. Some of them are symbiotic or suspected symbiotic stars, and one (He 2–61) is evidently not an emission object.

The Probable Low Excitation Planetary Nebula M3-44

The Hα emission object M3-44 was observed photographically and spectroscopically. Photographs were obtained in the visual region, in [0 III] λ5007, and in Hα. The visual image is faint and has almost stellar aspect; the object is not visible in [0 III], but the Ha image is very intense, with a diameter of the order of 5″.