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The near-IR NA I doublet and CA II triplet in late-type stars and the determination of stellar atmosphere parameters
CCD spectroscopic observations in the near-IR (7990-8680 A) for a sampleof 144 late type stars are presented. The dependence of the Na I doublet(8183 and 8194 A) and the Ca II triplet (8498, 8542 and 8662 A) onstellar atmospheric parameters is investigated. It is confirmed in starsof spectral types later than G0 a dependence of line strength oneffective temperature, surface gravity, and metallicity in goodagreement with previous studies. However, the present sample containsmany more very late type stars than previous studies, and these starsshow a strong dependence of Ca-II triplet strength on temperature. Theselines, together with the (R - I) color index which is known to be a goodtemperature indicator, were used to estimate the metal abundance and thesurface gravity of the present program stars.
| Instellar reddening in a high-latitude field around Omega Bootis
UBV observations have revealed an interstellar cloud with a visual totalextinction of 0.2 mag and a diameter of 1.5 pc at 60.5 deg galacticlatitude near Omega Bootis. The distance to the cloud is estimated atabout 25 pc. On the basis of the reddening values and by taking thebackground component into account, the intrinsic polarization of thecloud is calculated to be 0.0082 mag. The cloud's mass in neutralhydrogen is estimated at roughly 7 solar masses.
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Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Coban |
| Sað Açýklýk: | 14h47m47.42s |
| Yükselim: | +26°11'55.6" |
| Görünürdeki Parlaklýk: | 10.485 |
| özdevim Sað Açýklýk: | -18.6 |
| özdevim Yükselim: | 38.3 |
| B-T magnitude: | 10.937 |
| V-T magnitude: | 10.523 |
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