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A Young Super Star Cluster in the Nuclear Region of NGC 253
We present observations of a massive star cluster near the nuclearregion of the nearby starburst galaxy NGC 253. The peak of near-infrared(IR) emission, which is spatially separated by 4'' from the kinematiccenter of the galaxy, is coincident with a super star cluster whoseproperties we examine with low-resolution (R ~ 1200) infrared CerroTololo Inter-American Observatory spectroscopy and optical/near-IRHubble Space Telescope imaging. Extinction, measured from Fe II lines,is estimated at AV = 17.7 ± 2.6. The age of thecluster is estimated at 5.7 Myr, based on Br? equivalent width foran instantaneous burst using Starburst99 modeling. However, a complexstar formation history is inferred from the presence of bothrecombination emission and photospheric CO absorption. The ionizingphoton flux has a lower limit of 7.3 ± 2.5 ×1053 s-1, corrected for extinction. Assuminga Kroupa initial mass function, we estimate a cluster mass of~1.4+0.4 -0.5 × 107 Msun. We observe a strong Wolf-Rayet signature at 2.06 ?mand report a weak feature at 2.19 ?m which may be due to a massivestellar population, consistent with the derived mass and age of thiscluster.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
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| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| Standardization of stellar radial velocities in the presence of stellar rotation
Radial velocity standardization is reinvestigated, with emphasis on thepreviously neglected influence of stellar rotation, on the basis of 340spectrograms of 80 reference stars of spectral types B6-M0. Attention isgiven to the methods presently used to examine the influence of stellarrotation on the radial velocities obtained from individual lines and forthe selection of lines as free as possible from spectral type androtation dependence. This is done on the basis of observations of 68reference stars in the spectral type interval B6-F5, where the problemof rotation is most pronounced. In light of the accuracies achieved forstars of different rotations, a simple, rotation-independent criterionfor velocity variability is defined.
| A finding list of stars of spectral type A7 and earlier in regions at high galactic latitudes. VI. Near South Galactic Pole.
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Observation and Astrometry data
| Constellation: | ろ座 |
| Right ascension: | 01h59m19.58s |
| Declination: | -26°25'56.0" |
| Apparent magnitude: | 6.768 |
| Distance: | 135.87 parsecs |
| Proper motion RA: | 70.9 |
| Proper motion Dec: | 13.8 |
| B-T magnitude: | 6.821 |
| V-T magnitude: | 6.773 |
Catalogs and designations:
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