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J/A+A/409/933       UBVRI polarization in Stock 16           (Feinstein+, 2003)

Optical polarization observations in the region of Stock 16. Feinstein C., Baume G., Vergne M.M., Vazquez R.A. <Astron. Astrophys. 409, 933 (2003)> =2003A&A...409..933F
ADC_Keywords: Clusters, open ; Polarization; Photometry, UBVRI Keywords: open clusters and associations: Stock 16 Abstract: We present (UBVRI) multicolor linear polarimetric data for 26 of the brightest stars in the area of the open cluster Stock 16 that were considered to study the properties of the ISM (interstellar medium) towards the cluster. Our data yield a mean polarization percentage of P∼2.5%, close to the polarization value produced by the ISM with normal efficiency (Pλmax∼5EB-V_) undergoing a color excess of EB-V=0.51. The mean angle of the polarization vectors, θ=74.9deg, agrees quite well with the expected angle produced by dust particles aligned in the direction of the galactic disk (and the magnetic field) in the region. A study of the extinction suffered by the stars in the zone was also performed combining our new data with previous photometric data. In this sense, our analysis indicates that the visual absorption affecting Stock 16 stars is mainly produced in front of the cluster by a dust cloud at approximately 500 pc from the sun. The large polarization value of the non-member star, WR 51, confirms its background star nature. Description: Polarimetric data for 27 stars in the region of Stock 16 cluster obtained using the Torino five-channel photopolarimeter attached to the 2.15 m telescope at the Complejo Astron'omico El Leoncito in San Juan, Argentina. The stellar identification (column 1) are given by Turner (1985ApJ...292..148T) and we also included 4 stars indicated as A, B, C, D, not observed by Turner. In table1.dat, for each star in all the filters (UBVRI) are given the polarization percentage average (P_lambda, column 2) and the position angle of the electric vector (theta_lambda, column 3) with their respective mean errors computed according to Maronna, Feinstein and Clocchiatti (1992A&A...260..525M). The polarimetric observations in the five filters were fitted in each star using Serkowski's law (Serkowski, 1973, in IAU Symp. 52, Interstellar Dust and Related Topics, ed. J. M. Greenberg H. C. van de Hults (Dordrech: Reidel), p. 145) in table2.dat. In columns 2 and 4 are listed the values obtained for Pλmax and lambdamax with their respective errors. The column 3 shows the unit weight error of the fit (sigma1), to quantify the departure of our data from the theoretical curve of Serkowski's law. In the column 5 is listed the dispersion of the position angle normalized by the average of the position angle errors (ε). Objects: ---------------------------------------------------------- RA (2000) DE Designation(s) ---------------------------------------------------------- 13 19.1 -62 34 Stock 16 ---------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 34 133 Polarimetric observations of stars in Stock 16 table2.dat 48 27 Parameters of the Serkowski fit to the linear polarization data for stars in Stock 16
Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 10 A10 --- Name Star name (Star NNN, Star WR NN, Star A) 12 A1 --- Filter [UBVRI] Filter 15- 18 F4.2 % Pol Polarimetry 20- 23 F4.2 % e_Pol rms uncertainty on Pol 25- 29 F5.1 deg theta Position angle (North to East) 31- 34 F4.1 deg e_theta rms uncertainty on theta
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
1- 10 A10 --- Name Star name (Star NNN, Star WR NN, Star A) 13- 17 F5.3 % Pmax Maximum interstellar linear polarisation percentage 19- 23 F5.3 % e_Pmax rms uncertainty on Pmax 25- 29 F5.3 --- sigma1 Unit weight error of the fit (1) 31- 35 F5.3 um lambdamax Wavelength at which the maximum interstellar linear polarisation occurs, λmax 37- 41 F5.3 um e_lambdamax rms uncertainty on lambdamax 43- 48 F6.3 --- epsilon Dispersion of the position angle normalized by the average of the position angle errors
Note (1): sigma1>1.5 indicates the presence of intrinsic stellar polarization
Acknowledgements: Carlos Feinstein History: * 04-Nov-2003: table2 was added (kindly supplied by the author)
(End) Patricia Bauer [CDS] 25-Aug-2003
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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