UBV photoelectric photometry has been obtained for 37 red giant stars in the intermediate-age ope... more UBV photoelectric photometry has been obtained for 37 red giant stars in the intermediate-age open cluster NGC 6939 to study the morphology of the red giant branch in the colour-magnitude diagram. NGC 6939 presents a prominent clump. A second and fainter concentration is observed and should correspond to the slow-down of the evolution along the red giant branch occurring when
New photoelectric UBV observations of 16 stars in NGC 654 have been used to restandardize publish... more New photoelectric UBV observations of 16 stars in NGC 654 have been used to restandardize published photoelectric data. The compilation of the best data is used in conjunction with proper motions for a detailed analysis of the cluster. The distance-modulus for NGC 654 is (V- M V ) 0 = 12.00 (d = 2500 pc) and the reddening varies from E(B-V) = 0.74 to 1.19. The age, based on new models including the latest opacity tables, is 14.1 10 6 yr (log t = 7. 15). The F5 Ia supergiant (HD 10494) falls close to the blue end of the blue loop, which is a strong argument in favour of its membership. The present analysis confirms the tendency already observed to find the less reddened stars close to the cluster center
La photometrie UBV de 34 etoiles de l'amas NGC 436 et 27 etoiles de l'amas NGC 637 est pr... more La photometrie UBV de 34 etoiles de l'amas NGC 436 et 27 etoiles de l'amas NGC 637 est presentee. La distance, l'âge et le rougissement des amas sont determines.
Symposium - International Astronomical Union, 2000
We present the results of a lithium study of the 220 Myr old cluster NGC 6475. Our data are merge... more We present the results of a lithium study of the 220 Myr old cluster NGC 6475. Our data are merged with those from previous Li surveys of this cluster in order to construct a more statistically significant sample. The Li vs. effective temperature distribution of the merged sample is compared with the one of the co-eval, but more metal poor cluster M 34 and with the ones of the younger Pleiades and older Hyades. The results are discussed in the framework of non-standard Li depletion on the main-sequence between the age of the Pleiades (˜ 120 Myr) and that of the Hyades (˜ 600 Myr).
UBV photoelectric photometry has been obtained for 37 red giant stars in the intermediate-age ope... more UBV photoelectric photometry has been obtained for 37 red giant stars in the intermediate-age open cluster NGC 6939 to study the morphology of the red giant branch in the colour-magnitude diagram. NGC 6939 presents a prominent clump. A second and fainter concentration is observed and should correspond to the slow-down of the evolution along the red giant branch occurring when
New photoelectric UBV observations of 16 stars in NGC 654 have been used to restandardize publish... more New photoelectric UBV observations of 16 stars in NGC 654 have been used to restandardize published photoelectric data. The compilation of the best data is used in conjunction with proper motions for a detailed analysis of the cluster. The distance-modulus for NGC 654 is (V- M V ) 0 = 12.00 (d = 2500 pc) and the reddening varies from E(B-V) = 0.74 to 1.19. The age, based on new models including the latest opacity tables, is 14.1 10 6 yr (log t = 7. 15). The F5 Ia supergiant (HD 10494) falls close to the blue end of the blue loop, which is a strong argument in favour of its membership. The present analysis confirms the tendency already observed to find the less reddened stars close to the cluster center
La photometrie UBV de 34 etoiles de l'amas NGC 436 et 27 etoiles de l'amas NGC 637 est pr... more La photometrie UBV de 34 etoiles de l'amas NGC 436 et 27 etoiles de l'amas NGC 637 est presentee. La distance, l'âge et le rougissement des amas sont determines.
Symposium - International Astronomical Union, 2000
We present the results of a lithium study of the 220 Myr old cluster NGC 6475. Our data are merge... more We present the results of a lithium study of the 220 Myr old cluster NGC 6475. Our data are merged with those from previous Li surveys of this cluster in order to construct a more statistically significant sample. The Li vs. effective temperature distribution of the merged sample is compared with the one of the co-eval, but more metal poor cluster M 34 and with the ones of the younger Pleiades and older Hyades. The results are discussed in the framework of non-standard Li depletion on the main-sequence between the age of the Pleiades (˜ 120 Myr) and that of the Hyades (˜ 600 Myr).
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