SPECTROSCOPIC INVESTIGATIONS OF GALACTIC CLUSTERS WITH ASSOCIATED CEPHEID VARIABLES. IV. COLLINDER 220 AND UW CAR
DOI:
https://doi.org/10.18524/1810-4215.2020.33.216285Ключові слова:
Open clusters, radial velocities, Stars, abundance, GAIA parallaxes, Cepheids, B - giants, K-giants, individual, Collinder 220, UW Car, CPD −57 ◦ 3199, HD 90435, HD 90552, HD 302751, HD 302759, HD 302760, HD 302761, HD 302858, TYC 8608-1-1, TYC 8608-25-1Анотація
We present the results of a spectro-
scopic and photometric investigation of 18 probable
members of the open cluster Collinder 220, which
contains the Cepheid UW Car. Besides the Cepheid,
we studied tree K-giants, two B-giants, and twelve
B-A-F main sequence stars. Radial velocities (RV),
vsini, T eff , and logg were determined using spec-
troscopic model fitting and atmosphere models. We
have derived color-excesses, reddenings, and intrinsic
colors for these stars using their T eff and logg from
comparison to the atmosphere models, especially
for hot stars. Proper motions, RV, and the GAIA
DR2 2018 parallaxes allowed us to determine their
membership in the cluster and absolute magnitudes.
We found that seven stars along with the Cepheid can
be the cluster members with a high confidence. The
parallaxes and reddenings of the 7 confident cluster
members led to the distances in a range of 1900–2800
pc, while the other stars are probably foreground
objects. All the members have [Fe/H] near 0.1 dex.
The B-giant HD90435 located near the cluster’s
“turn-off” point has a low projected rotational veloc-
ity, and this fact allows us to determine its chemical
composition to compare with that of the Cepheid UW
Car. The CNO abundances of HD90435 are nearly
solar, while the Cepheid shows a deficit of carbon, an
overabundance of nitrogen, a nearly solar oxygen, and
an overabundance of sodium. The confident cluster
member, K-supergiant CPD −57 ◦ 3199, has CNO- and
Na abundances close to those of UW Car.
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