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Optical polarimetry, high--resolution spectroscopy and IR analysis of the Chamaeleon I dark cloud
We present optical polarimetry and high resolution spectroscopy of asample of stars toward the Chamaeleon I dark cloud. We use ourpolarimetry which includes 33 stars to study the wavelength dependenceof the degree and position angle of polarization. From fits to thenormalized wavelength dependence of interstellar polarization, we deriveestimates of lambdaMax ranging from 4500 \AA to 6700 \AA, andPMax ranging from 3 to 8%. The values of lambdaMaxwere found to be well correlated with the IRAS 100 micron intensity,while PMax was found to increase with E_{B-V}. Highresolution spectra of the Ca II, CH, and CH^{+} lines were obtained for10 stars, which show two components of Ca II in absorption at 3.0
| On the distance to the Chamaeleon I and II associations
Constraints on the distances to the dark clouds Chamaeleon I and II areinvestigated in detail. A compilation of photometric data, spectraltypes and absolute magnitudes for field stars towards each cloud ispresented, and results are used to examine the distribution of reddeningwith distance along each line of sight. The distances to starsassociated with reflection nebulae in each cloud are examined in detail.On the basis of these results, we deduce the most probable distance ofCha I to be 160+/-15pc, and that of Cha II to be 178+/-18pc. Anexamination of the mean fluxes of T Tauri stars in each cloud providesindependent evidence to suggest that Cha II is significantly moredistant than Cha I. Both clouds appear to be embedded in a macroscopicsheet-like structure extending over much of the Chamaeleon-Musca-Cruxregion. The Chamaeleon III and DC\ts 300.2--16.9 clouds are probablypart of the same structure, with probable distances ~ 140--160pc.
| A Study of the Chamaeleon-I Dark Cloud and T-Association - Part Six - Interstellar Polarization Grain Alignment and Magnetic Field
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1994MNRAS.268....1W&db_key=AST
| Four-colour UVBY and H-beta photometry of all stars earlier than G0 and brighter than MPG of about 10.7 M in Selected Area 203 towards the Chamaeleon-Musca dark clouds
Results are presented of Stromgren uvby(beta) photometry for 213 starsearlier than G0 and brigher than mpg of about 10.7 m inSelected Area 203. The observed area lies close to the geometric centerof the Chamaeleon-Musca dark clouds complex. The results yield V, (b-y),m1, c1, and beta on the standard systems, withoverall rms errors for one observation of one star of 0.010, 0.004,0.007, 0.009, and 0.011, respectively.
| A study of the Chamaeleon dark cloud and T-association. I - Extinction, distance and membership
The results of an observing program to investigate the nature and degreeof reddening of a number of stars in the field towards the dark cloudand T-association in Chamaeleon are presented. The observations compriseoptical (UBVRI) and infrared (JHK) photometry, and optical spectroscopy.New and previously published data are combined to assess membershipcriteria for 110 stars, and separate catalogues of association membersand field stars are presented. Optical identifications are listed for 27IRAS point sources in the region. The reddening/distance relation forfield stars indicates a distance to the cloud of 140 + or - 12 pc. Thisresult confirms that the extinction law is anomalous towards some starsin the cloud, notably the embedded A0 ZAMS star HD 97300, with values ofup to 5.5 for the ratio of total-to-selective extinction. A comparisonof 21-cm data with the reddening of background field stars indicatesthat the ratio N(H I)/E(B-V) is significantly less than the interstellarmean, indicating that most of the hydrogen in the cloud is molecular.
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| Takýmyýldýz: | Bukalemun |
| Sað Açýklýk: | 11h21m57.10s |
| Yükselim: | -77°36'30.0" |
| Görünürdeki Parlaklýk: | 6.43 |
| Uzaklýk: | 74.627 parsek |
| özdevim Sað Açýklýk: | -77.5 |
| özdevim Yükselim: | -12.3 |
| B-T magnitude: | 6.672 |
| V-T magnitude: | 6.449 |
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