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Optical multicolor polarization observations in the region of the open cluster NGC 5749
We present (UBVRI ) multicolor linear polarimetric data for 31 of thebrightest stars in the area of the open cluster NGC 5749 considered tostudy the properties of the interstellar medium (ISM) towards thecluster. Our data yield a mean polarization percentage of PV˜ 1.7%, close to the polarization value produced by the ISM withnormal efficiency (P(%)=3.5 {E(B-V)}0.8) for amean color excess of EB-V=0.42. The mean angle ofpolarization vectors, θ=74°, agrees quite well with theexpected angle produced by dust particles aligned in the direction ofthe galactic disk (and the magnetic field) in the region. Our analysisindicates that the visual absorption affecting the stars in NGC 5749 ispartially produced by a dust layer located up to 300 pc from the Sun andalso by a second layer of dust closer to the cluster (located at leastat 700 pc). The observed photometry and our polarization data areconsistent with the existence of dust within the cluster. We also showin this work how polarimetry could be an excellent technique foridentifying nonmember stars.Based on observations obtained at Complejo Astronómico ElLeoncito (CASLEO), operated under agreement between the CONICET and theNational Universities of La Plata, Córdoba, and San Juan,Argentina. Table 1 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/462/621
| Absolute proper motions of open clusters. I. Observational data
Mean proper motions and parallaxes of 205 open clusters were determinedfrom their member stars found in the Hipparcos Catalogue. 360 clusterswere searched for possible members, excluding nearby clusters withdistances D < 200 pc. Members were selected using ground basedinformation (photometry, radial velocity, proper motion, distance fromthe cluster centre) and information provided by Hipparcos (propermotion, parallax). Altogether 630 certain and 100 possible members werefound. A comparison of the Hipparcos parallaxes with photometricdistances of open clusters shows good agreement. The Hipparcos dataconfirm or reject the membership of several Cepheids in the studiedclusters. Tables 1 and 2 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| New color-magnitude diagrams and basic parameters of the open cluster NGC 5749
New photoelectric UBV magnitudes and colors for 112 stars and DDOphotometry of two red stars in the field of the open cluster NGC 5749are presented. Using photometric membership criteria, only 30 percent ofthe observed stars appear to be cluster members, including one suspectedvariable star. The cluster does not probably contain any red giant. Thereddening is variable across the cluster, the mean value being E(B - V)= 0.42 +/- 0.04 (s.d.). A distance of (1280 +/- 118) pc, an age of 2.7 x10 exp 7 yr and other basic cluster parameters are derived.
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