J/AJ/160/256 Polarization of 125 stars in NGC 1817 open cluster (Singh+, 2020)
Broadband linear polarization in the region of the open star cluster NGC 1817.
Singh S., Pandey J.C.
<Astron. J., 160, 256 (2020)>
=2020AJ....160..256S 2020AJ....160..256S
ADC_Keywords: Clusters, open; Interstellar medium; Photometry, UBVRI;
Polarization
Keywords: Starlight polarization ; Polarimeters ; Open star clusters ;
Interstellar dust ; Interstellar dust extinction ;
Iterstellar medium
Abstract:
Multiband linear polarimetric observations of 125 stars in the region
of the cluster NGC1817 have been carried out intending to study
properties of interstellar dust and grains in that direction. The
polarization is found to be wavelength-dependent, being maximum in the
V-band with an average value of 0.95%. The foreground interstellar
dust grains appear to be the main source of linear polarization of
starlight toward the direction of NGC1817. The average value of the
position angle in the V-band of 119.2° is found to be less than
the direction of the Galactic parallel in the region, indicating that
the dust grains in the direction are probably not yet relaxed. Spatial
distribution of dust appears to be more diverse in the coronal region
than the core region of the cluster. The maximum value of the degree
of polarization is estimated to be 0.93% for members of the cluster
using the Serkowski relation. The average value of wavelength
corresponding to the maximum polarization of 0.54±0.02µm
indicates that the size distribution of dust grains in the line of
sight is similar to that of the general interstellar medium. Several
variable stars in the cluster were also observed polarimetrically and
pulsating variables appear to have a slightly lower value of
polarization from other nonvariable member stars of the cluster. There
are indications of the existence of dust layers in front of those
clusters which are located close to galactic plane while for clusters
located away from galactic plane no major dust layers are observed.
Description:
We have observed the cluster NGC1817 by using the Aries IMaging
POLarimeter (AIMPOL) on 2018 January 18, 19, and 22 in four passbands
B, V, R, and I. The AIMPOL is mounted as a backend of the 104cm
Cassegrain telescope of Aryabhatta Research Institute of Observational
Sciences (ARIES). The exposure times were in the range of 60-250s in
different bands.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 118 125 Results of the broadband polarimetric observations
of all stars toward the cluster NGC1817
table3.dat 29 75 Parameters Pmax, lmax as obtained from fitting the
Serkowski relation
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See also:
II/178 : Linear polarization measurements for 5070 stars (Axon+ 1976)
II/226 : Stellar polarization catalogs agglomeration (Heiles, 2000)
I/337 : Gaia DR1 (Gaia Collaboration, 2016)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
I/349 : StarHorse, Gaia DR2 photo-astrometric distances (Anders+,2019)
V/96 : Catalogue of open cluster parameters from UBV-data.(Loktin+, 1994)
VII/244 : Atlas and Catalog of Dark Clouds (Dobashi+, 2005)
J/ApJS/2/389 : Observations of O and B stars (Hiltner, 1956)
J/A+A/359/347 : Reddening in open and globular clusters (Dutra+, 2000)
J/A+A/426/819 : NGC1817 proper motions and membership (Balaguer-Nunez+,2004)
J/A+A/438/1163 : Catalogue of Open Cluster Data (COCD) (Kharchenko+, 2005)
J/A+A/463/789 : Blue stragglers in open clusters (Ahumada+, 2007)
J/A+A/462/621 : UBVRI polarisation in NGC 5749 (Vergne+, 2007)
J/MNRAS/399/2146 : Orbits of open clusters in the Galaxy (Wu+, 2009)
J/MNRAS/403/1577 : Polarization towards open cluster NGC 6823 (Medhi+, 2010)
J/A+A/513/A75 : Polarimetry of stars in NGC 5617 (Orsatti+, 2010)
J/A+A/522/A88 : Photometric identification of BHB stars (Smith+, 2010)
J/MNRAS/403/2041 : Optical polarization in NGC 6124 (Vergne+, 2010)
J/PASJ/63/S1 : Atlas & catalog dark clouds based on 2MASS (Dobashi+, 2011)
J/AJ/142/59 : Chemical abundance in 10 open clusters (Jacobson+, 2011)
J/A+A/548/A97 : Catalogue of variable stars in open clusters (Zejda+, 2012)
J/ApJ/764/172 : UBVRI photometry of stars toward NGC 1931 (Pandey+, 2013)
J/A+A/618/A93 : Gaia DR2 open clusters in Milky Way (Cantat-Gaudin+, 2018)
J/A+A/620/A172 : Solar neighbourhood young stars 3D mapping (Zari+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/125] Sequential number identification
5- 9 A5 --- f_Seq Flag(s) on Seq (1)
11- 29 I19 --- Gaia Gaia DR2 identification
31- 34 F4.2 arcsec Offset [0.02/1.21] Offset from Gaia DR2 position
36- 39 F4.2 % P(B) [0.23/2.33]? Degree of polarization in B-band
41- 44 F4.2 % e_P(B) [0.01/0.8]? Error in P(B)
46- 50 F5.1 deg PA(B) [65.6/180]? Polarization angle in B-band
52- 55 F4.1 deg e_PA(B) [0.1/15]? Error in PA(B)
57- 60 F4.2 % P(V) [0.45/1.81]? Degree of polarization in V-band
62- 65 F4.2 % e_P(V) [0.01/0.71]? Error on P(V)
67- 71 F5.1 deg PA(V) [83.3/167]? Polarization angle in V-band
73- 76 F4.1 deg e_PA(V) [0.1/14.1]? Error in PA(V)
78- 81 F4.2 % P(R) [0.44/2.91]? Degree of polarization in R-band
83- 86 F4.2 % e_P(R) [0.01/0.92]? Error in P(R)
88- 92 F5.1 deg PA(R) [80.6/178]? Polarization angle in R-band
94- 97 F4.1 deg e_PA(R) [0.1/14.7]? Error in PA(R)
99-102 F4.2 % P(I) [0.12/1.34]? Degree of polarization in I-band
104-107 F4.2 % e_P(I) [0.01/0.41]? Error in P(I)
109-113 F5.1 deg PA(I) [67/179]? Polarization angle in I-band
115-118 F4.1 deg e_PA(I) [0.1/14.5]? Error in PA(I)
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Note (1): Flags as follows:
* = Member stars (58 occurrences)
a = giants, Sandquist+, 2020AJ....159...96S 2020AJ....159...96S (18 occurrences)
b = pulsating stars, Sandquist+, 2020AJ....159...96S 2020AJ....159...96S (20 occurrences)
c = blue stragglers, Ahumada+, 2007, J/A+A/463/789 (5 occurrences)
d = eclipsing binaries, Sandquist+, 2020AJ....159...96S 2020AJ....159...96S (3 occurrences)
e = blue horizontal branch stars, Smith+, 2010, J/A+A/522/A88 (1 occurrence)
f = pre-main-sequence stars, Zari+, 2018, J/A+A/620/A172 (1 occurrence)
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/109] Sequential number identification
5 A1 --- f_Seq [*] Flag indicating members stars (49 occurrences)
7- 10 F4.2 % Pmax [0.44/4.83] Maximum polarization
12- 15 F4.2 % e_Pmax [0.01/1.23] Error on Pmax
17- 20 F4.2 um lambda [0.2/1.03] Wavelength corresponding to Pmax
22- 25 F4.2 um e_lambda [0.01/0.36] Error on lambda
27- 29 F3.1 --- sigma1 [0/2.4] sigma1 (σ1) value
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History:
From electronic version of the journal
(End) Prepared by Coralie Fix [CDS], 17-Feb-2021