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מאמרים קשורים
On the highly reddened members in six young galactic star clusters - a multiwavelength study
The spectral and reddening properties of 211 highly reddenedproper-motion members with V < 15 mag in six young galactic starclusters are investigated using low-resolution spectroscopic, broad-bandUBVRIJHK and mid-infrared (IR) data. We report emission features in CaIIHK and HI lines for a sample of 29 stars including 11 stars reported forthe first time and also provide either a new or more reliable spectralclass for a sample of 24 stars. CaII triplet width measurements are usedto indicate the presence of an accretion disc for a dozen stars and toindicate luminosity for a couple of stars. On the basis of spectralfeatures, near-IR excesses, dereddened colour-colour diagrams and mid-IRspectral indices we identify a group of 28 pre-main-sequence clustermembers including five highly probable Herbig Ae/Be and six classical TTauri stars. A total of 25 non-emission main-sequence (MS) stars,amounting to ~10 per cent early-type MS members, appears to showVega-like characteristics or are precursors to such a phenomenon. Thevarious membership indicators suggest that ~16 per cent of theproper-motion members are non-members. A significant fraction (>70per cent) of programme stars in NGC 1976, NGC 2244, NGC 6530 and NGC6611 show anomalous reddening with RV= 4.78 +/- 0.10, 3.54+/- 0.04, 3.87 +/- 0.05 and 3.56 +/- 0.02, respectively, indicating thepresence of grain size dust larger than that typical of the diffusemedium. A small number of stars in NGC 1976, NGC 2244 and NGC 6611 alsoshow normal behaviour while the cluster NGC 6823 appears to have normalreddening. Three highly luminous late-type giants, one in NGC 2244 andtwo in NGC 6530, appear to be members and are inpost-hydrogen-core-burning stages, suggesting a prolonged duration (~25Myr) of star formation.
| Observations of Star-Forming Regions with the Midcourse Space Experiment
We have imaged seven nearby star-forming regions, the Rosette Nebula,the Orion Nebula, W3, the Pleiades, G300.2-16.8, S263, and G159.6-18.5,with the Spatial Infrared Imaging Telescope on the Midcourse SpaceExperiment (MSX) satellite at 18" resolution at 8.3, 12.1, 14.7, and21.3 μm. The large angular scale of the regions imaged (~7.2-50deg2) makes these data unique in terms of the combination ofsize and resolution. In addition to the star-forming regions, twocirrus-free fields (MSXBG 160 and MSXBG 161) and a field near the southGalactic pole (MSXBG 239) were also imaged. Point sources have beenextracted from each region, resulting in the identification over 500 newsources (i.e., no identified counterparts at other wavelengths), as wellas over 1300 with prior identifications. The extended emission from thestar-forming regions is described, and prominent structures areidentified, particularly in W3 and Orion. The Rosette Nebula isdiscussed in detail. The bulk of the mid-infrared emission is consistentwith that of photon-dominated regions, including the elephant trunkcomplex. The central clump, however, and a line of site toward thenorthern edge of the cavity show significantly redder colors than therest of the Rosette complex.
| Infrared carbon stars: new identifications and their space distribution in the Galaxy
We present JHKL photometry of a sample of 150 IRAS stars in the thirdand fourth galactic quadrant with | b | <2(deg) selected according totheir IRAS colour (0.160<=[12-25]<=1.156). We identify 27 carbonstar candidates using the [12-25] vs. K-L two-colour diagram method.Among them, 10 are listed in the Stephenson's catalogue of carbon starsand 17 are new infrared carbon stars (IRCS) candidates. Their distancesare found to be larger than 3 kpc. These data are combined with previousdata to study the space distribution of IRCS. The number density seemsto be independent of the galactocentric distance (R) toward the GalacticCenter and to decrease exponentially toward the anticenter. At thepresent stage, it is not possible to disentangle effects such asincompleteness of the sample, different space distribution law anddependence of the luminosity on metallicity. In particular, we suggestthat the apparent scarcity of IRCS in the central direction of theGalaxy (R<5 kpc) might be due to a selection effect. From theavailable data, we have found no IRCS within 1 kpc of the GalacticCenter. Based on observations obtained at the European SouthernObservatory, Chile
| UBV Photometry of NGC2244
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1981PASJ...33..149O&db_key=AST
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | חד קרן |
| התרוממות ימנית: | 06h33m44.05s |
| סירוב: | +05°12'57.5" |
| גודל גלוי: | 8.862 |
| תנועה נכונה: | -3.1 |
| תנועה נכונה: | 0.7 |
| B-T magnitude: | 11.831 |
| V-T magnitude: | 9.108 |
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