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 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 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 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:
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RA (2000) DE Designation(s)
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13 19.1 -62 34 Stock 16
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File Summary:
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FileName Lrecl Records Explanations
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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
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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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
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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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
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Note (1): sigma1>1.5 indicates the presence of intrinsic stellar polarization
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Acknowledgements: Carlos Feinstein
History:
* 04-Nov-2003: table2 was added (kindly supplied by the author)
(End) Patricia Bauer [CDS] 25-Aug-2003