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Spectral Classification of Stars in A Supplement to the Bright Star Catalogue
MK spectral types are given for about 584 stars in A Supplement to theBright Star Catalogue. These are compared with Hipparcos parallaxes tocheck the reliability of those classifications. The estimated errors are+/-1.2 subtypes, and 10% of the luminosity classes may be wrong.
| Distances of absorbing features in the LDN 1622 direction. An application of Tycho-2 photometry and Michigan Classification
With Tycho-2 BT and VT photometry of Hipparcosstars with π > 8.0 mas, σπ/π < 15% andwith spectral type and luminosity classification from the MichiganCatalogues we have a presumably unreddened sample for establishing a(BT-VT_0- MV_T main sequence relationin the range from A0 to G5. We discuss the location of the median mainsequence relation relative to published ZAMS relations for the A0-G5range in some detail since the applications of this relation will haveto assume that the evolutionary status of the calibration sample isrepresentative of the local disk. If the ZAMS is defined as the lowerenvelope of the class V stars the published versions we discuss seem tobe too bright by about half a magnitude in the F0-G5 range. Theresulting intrinsic color and absolute magnitude estimates have errorsof the mean of 0.03m and 0.3m-0.4m respectively. From this relation anygiven star with Tycho-2 photometry, spectral classification andluminosity class V can have its color excess E(BT -VT) and distance modulus estimated. This means that the localinterstellar extinction may be estimated for the ~50% of the sky whereMichigan classification presently is available. The individual colorexcesses and distance moduli may not be particularly accurate but wepropose that they may be used to indicate extinction discontinuitiescaused by interstellar material at well defined distances. We haveapplied this new technique on stars from the Michigan Catalogue in thedirection of LDN 1622 (l, b) = (204.7dg, -11.8dg) supposed to beassociated to the Orion B region 400-500 pc away but color excessesE(BT - VT) exceeding 0.15m start appearing alreadyin the distance slot 160-200 pc. Presently we cannot decide whether thisnearby dust is related to LDN 1622 or whether this cloud is associatedto Orion B. In a final comparison we study the color excess -- distancevariation in a 4 deg region centered on LDN 1622 from Hipparcos --Tycho-1 -- Michigan data and the dust at ~160 pc is confirmed.
| First radial velocities for 146 bright F- and G-type stars
We have obtained an average of 5.7 radial velocities for 146 northernstars of types F and G (all luminosity classes) listed in 'A Supplementto the Bright Star Catalogue' as having no previously known radialvelocity measures. Those were obtained with charge coupled devices(CCDs) and a cross-correlation technique; the intrinsic velocityaccuracy, based on stars of apparently constant velocity, is probablyless than +/- 0.3 km/s per mean. Of those stars 14% are newly discoveredSB2 stars. The prevelance of rapid profile variations (in minutes orhours) in most of the broad-lined F-type stars makes it difficult toobtain accurate measures for them.
| VRI photometry of selected SAO stars
Johnson V, R, and I photoelectric photometry has been obtained for 199SAO stars in support of the Near Infrared Photographic Sky Survey. Thesedata are utilized in the calibration of survey photographs and arepresented here to assist other programs reliant upon access tophotometry in the photographic infrared.
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Besorolás csoportokba:
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Pozíciós és asztrometriai adatok
| Csillagkép: | Orion |
| Rektaszcenzió: | 06h00m49.32s |
| Deklináció: | +02°54'57.6" |
| Vizuális fényesség: | 6.975 |
| Távolság: | 233.645 parszek |
| RA sajátmozgás: | -11.4 |
| Dec sajátmozgás: | 0.6 |
| B-T magnitude: | 8.115 |
| V-T magnitude: | 7.07 |
Katalógusok és elnevezések:
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