ALBERT

Description: It has been determined that the absolute position of the centroid of SiO maser-emitting spots toward both R Aqr and Omicron Cet are coincident with the position of the long-period variables (LPVs) in these binary systems to within the errors of measurement. The SiO positions were determined with the Hat Creek interferometer, while the LPV positions were determined with the 8-in transit circle of the US Naval Observatory. These results contradict an earlier report of a circumbinary SiO maser far removed from the LPV in the R Aqr binary system; statistical reasons for the discrepancy are suggested. High-resolution spectra of both sources are presented and possible models are discussed.

Description: VLA observations with a limiting spatial resolution of about 0.15 arcsec were attempted along with complementary observations of SiO emission using the three-element Hat Creek interferometer to determine an accurate position of the long-period variable (LPV) of the R Aquarii binary system. The observations indicate that the LPV wind is distorted by the photoionization of the hot campanion's accretion disk, that precession of the accretion disk may occur, and that the observed v = 1, J = 2-1 transition emanates from a circumbinary layer far removed from the position of the LPV itself.

Description: The first detection of interference fringes by VLBI at a wavelength of 3.4 mm during observations of 3C84 are reported. The compact source in the nucleus of 3C84 was observed for a 9-hr period on the 485 km baseline between the Owens Valley Radio Observatory and the Hat Creek Observatory. The fringe data are given and the derivation of the correlated flux densities is described. The findings are discused in the context of previous obervations. The results demonstrate that there are no unforeseen technical difficulties associated with millimeter VLBI, and that the sensitivity of existing systems is sufficient to observe objects brighter than a few Jy. The observations are consistent with the millimeter wavelength radio structure of 3C84 being more compact than its centimeter wavelength structure.

Description: Reported are 88 GHz aperture synthesis observations of HCN J=1 yields 0 emission and absorption in the central 5 pc of the Galaxy. The data, taken by the Hat Creek mm-interferometer at 5" to 10" spatial and 4 km/s spectral resolution, show a complete, clumpy ring of molecular gas surrounding the ionized central 2 pc of the Galaxy. The ring is the inner edge of a larger disk extending to about 5 pc. Comparison with sub-mm line data suggests that the HCN 1-0 line is slightly optically thick and originates in subthermally populated gas. The clumpy line emission distribution reflects a combination of hydrogen volume and column density variations. The new data clearly show a close physical relation between the molecular and the ionized gas in the central cavity. The western arc appears to be the ionized inner surface of the molecular ring, and the northern arm and bar may be streamers of ionized gas falling from the ring toward the center. The dominant large scale velocity pattern of the majority of the molecular gas in the inner 5 pc is rotation. No overall radial motion of the ring greater than about 20 km/s is apparent. The rotation is perturbed in several ways; (1) there is a very large local velocity dispersion, (2) the ring shows changes in position angle and inclination (warps), (3) there is a bright, redshifted cloud which appears to be located in the western part of the ring but does not participate in the rotation. These characteristics and the high degree of clumpiness indicate a non-equilibrium configuration of short (less than or approx. 10 to the 4th power to 10 to the 5th power y) dynamical lifetime. The warping and tilting of the structure and the short dynamical lifetime make an accurate determination of equilibrium rotation velocity uncertain.

Description: DR 21 has been observed in the J = 1-0 line of HCN with a resolution of 12.5 by 15.5 arcsec using the mm-wave interferometer at the Hat Creek Observatory. The HCN line is seen in both emission and absorption as an isolated clump immediately adjacent to the compact H II regions of DR 21. The full extent of the clump is about 30 arcsec in R.A. and 60 arcsec in decl. which corresponds to 0.3 by 0.6 pc for an assumed distance of 2 kpc. The mass of the clump is estimated to be about 200 solar masses. Two velocity components are present: the more intense one at -5 km/s is only seen in emission, and the other at -2.4 km/s is seen in emission in the northwest and mostly in absorption against the continuum source. The component at -5.0 km/s is identified to have higher excitation, and the one at -2.4 km/s to have greater column density.

Description: W3 has been observed in the J = 1-0 transition of HCN with the millimeter-wave interferometer at the Hat Creek Observatory with a resolution of 11.5 by 11.1 arcsec. The HCN emission is detected in an isolated cloud with a diameter of 40 arcsec. The cloud is located to the south of IRS 4 and the compact H II region C and coincides with the western far-IR cloud mapped at 400 microns by Jaffe (1983). The total mass of the cloud is estimated to be in the range 250-2500 solar masses. No HCN emission was detected around IRS 5, the location of the other 400 micron peak. Also, no evidence for a new (heretofore undetected at other wavelengths), young main-sequence star earlier than B0 was found in the new continuum map at 3 mm.