Astrophysical properties of red giants in three open clusters older than the hyades

Results fromCMT ₁T₂ 1T2 broad-band and DDO intermediate-band photometry are presented for G and K giants in the old open clusters NGC. 2482, NGC 3680, and IC 4651. Two independent photometric criteria have been used to separate red field stars from the physical members of the clusters. Recent calibrations of the DDO andCMT ₁T₂ systems have been used to derive reddening, distance moduli, metallicities, effective temperatures, and surface gravities. Rough estimates of masses have also been made. The giants of NGC 2482 and IC 4651 have CN strengths nearly identical to the Hyades giants, while those of NGC 3680 are slightly richer in CN than the nearby K giants.CMT1T2 abundance analysis in NGC 2482 and NGC 3680 yield [Fe/H]_MT = - 0.1 ± 0.1 as derived from the iron lines, while abundances derived from the CNO - contaminated (C - M) index are 0.4 dex higher. BothCMT ₁T₂ and DDO data support the conclusion that 1C 4651, with [Fe/H] = + 0.2 ± 0.1, is on the metalrich side of the distribution of intermediate and old open clusters. Finally, the mass results suggest that the clump stars in NGC 3680 and. IC 4651 could have undergone mass loss before reaching their helium core burning phase of evolution. Supported in part by the Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) of Argentina. Visiting astronomer of Cerro Tololo Inter-American Observatory supported by the National Science Foundation under contract No. AST 74-04128.     

Observations of C2 Molecules in the Coma of Comets at Mitaka

In order to monitor the various phenomena of comets, we continuously made the near-nucleus imaging observations of comets at National Astronomical Observatory, Mitaka. Here we report on the results of the observations of two spectacular comets. One is the analysis of photometry of C₂ emission images in the coma of comet Hyakutake (C/1996 B2). By comparing the production rates of C₂ radicals with C₂H₂ molecules, we conclude that the most C₂ radicals were originated from C₂H₂, while some of them might be produced from other parents. The second item is the analysis of the morphology of C₂ emission images in the coma of comet Hale-Bopp(C/1995 O1). By applying a ring masking technique, we detected asymmetrical distribution of the C₂ molecules. The results of these two comets might suggest that a portion of C₂ radicals were formed by the disintegration of the small organic dust grains, like the so-called CHON particles. This revised version was published online in July 2006 with corrections to the Cover Date.