J/AJ/159/214 UBVRI linear polarisation in Wolf-Rayet winds (Fullard+, 2020)
A multiwavelength search for intrinsic linear polarization in Wolf-Rayet winds.
Fullard A.G., St-Louis N., Moffat A.F.J., Piirola V.E., Manset N.,
Hoffman J.L.
<Astron. J., 159, 214 (2020)>
=2020AJ....159..214F 2020AJ....159..214F
ADC_Keywords: Stars, Wolf-Rayet; Stars, double and multiple; Surveys;
Polarization; Optical
Keywords: Wolf-Rayet stars ; Binary stars ; Polarimetry ; Surveys ;
Astronomical reference materials ; Massive stars
Abstract:
Wolf-Rayet (WR) stars have strong, hot winds, with mass-loss rates at
least a factor of 10 greater than their O-star progenitors, although
their terminal wind speeds are similar. In this paper, we use the
technique of multiband linear polarimetry to extract information on
the global asymmetry of the wind in a sample of 47 bright Galactic WR
stars. Our observations also include time-dependent observations of 17
stars in the sample. The path to our goal includes removing the
dominating component of wavelength-dependent InterStellar Polarization
(ISP), which normally follows the well-known Serkowski law. We include
a wavelength-dependent ISP position angle parameter in our ISP law and
find that 15 stars show significant results for this parameter. We
detect a significant component of wavelength-independent polarization
due to electron scattering in the wind for 10 cases, with most WR
stars showing none at the ∼0.05% level precision of our data. The
intrinsically polarized stars can be explained with binary
interaction, large-scale wind structure, and clumping. We also found
that 5 stars out of 19 observed with the Stromgren b filter (probing
the complex λ4600-4700Å emission-line region) have
significant residuals from the ISP law and propose that this is due to
wind asymmetries. We provide a useful catalog of ISP for 47 bright
Galactic WR stars and upper limits on the possible level of intrinsic
polarization.
Description:
We obtained our multiband polarimetry in two observing runs, one in
the North at the 1.25m Crimean Observatory telescope in
1989-September, the other in the South at the 1.5m ESO/La Silla
telescope in 1991-May. Both these telescopes were equipped with a
simultaneous five-channel polarimeter designed and built by V.
Piirola. At La Silla the phototube in the I-band was malfunctioning,
so we replaced this filter with a medium band Stromgren b filter to
simulate partial spectropolarimetry. Only the brightest stars had
enough flux to give useful data in this narrower filter.
Objetcs:
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RA (ICRS) DE Designation(s)
---------------------------------------------------------------
20 05 57.32 +35 47 18.2 WR133 = Gaia DR2 2059076148587289728
20 10 14.19 +36 10 35.1 WR134 = Gaia DR2 2059146654767199872
---------------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table3.dat 52 224 *Mean polarization data for all our targets
tablea1.dat 121 24 *Observational data for objects with fewer than 5
observations
tablea2.dat 134 47 Polarimetric observations of WR 133, observed at
the Crimean Observatory
tablea3.dat 128 18 Polarimetric observations of WR 134, observed at
the Crimean Observatory.
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Note on table3.dat : Calculated as described in Section 3 of the article.
Note on tablea1.dat : All objects in this table were observed at ESO/La Silla.
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See also:
III/215 : 7th Catalog of Galactic Wolf-Rayet stars (van der Hucht, 2001)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/AJ/120/2101 : Radial Velocity and Photometry of HD 104994 (Marchenko+, 2000)
J/A+A/458/453 : Annex to 7th Cat. of Galactic WR Stars (van der Hucht, 2006)
J/A+A/462/621 : UBVRI polarisation in NGC 5749 (Vergne+, 2007)
J/A+A/471/165 : UBVRI polarisation in NGC 5606 (Orsatti+, 2007)
J/ApJS/176/59 : FUSE survey of OVI in the disk of the Milky Way (Bowen+, 2008)
J/A+A/531/A25 : Linear & circular polarisation spectra of 2 stars (Cox+,2011)
J/AN/332/616 : V444 Cyg BV differential light curves (Eris+, 2011)
J/A+A/556/A65 : LDN 1570 BV(RI)c polarisation & photometry (Eswaraiah+, 2013)
J/A+A/608/A146 : Southern Hemis. ISMFORS2 spectropolarimetry (Bagnulo+, 2017)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- WR [1/157] WR catalog number (WR N)
5- 8 A4 --- Var Variability source (1)
10- 11 A2 --- Mean Mean fit type
13- 14 I2 --- Num [1/71] Number of observations
16- 24 F9.4 d HJD [7760/8418]? Heliocentric Julian Date; HJD-2440000
26- 26 A1 --- Band Observed band
28- 33 F6.3 % q [-6.45/2.47] Percent Stokes Q/I
35- 39 F5.3 % e_q [0.005/0.52] Error in q
41- 46 F6.3 % u [-6.7/4.28] Percent Stokes U/I
48- 52 F5.3 % e_u [0.005/0.52] Error in u
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Note (1): Sources as Follows:
CIR = Co-rotating interaction regions (5 occurrences)
CIR? = Candidate co-rotating interaction regions (9 occurrences)
SB1 = Single-lined spectroscopic binary (18 occurrences)
SB1? = Candidate single-lined spectroscopic binary (14 occurrences)
SB2 = Double-lined spectroscopic binary (98 occurrences)
SB2? = Candidate double-lined spectroscopic binary (10 occurrences)
VB = Visual binary (9 occurrences)
? = unknown (4 occurrences)
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- WR [16/113] WR catalog designation (WR N)
5- 12 F8.4 d HJD [410/418] Heliocentric Julian date; HJD-2440000 (1)
14- 19 F6.3 % Uq [-3.22/-0.06] U band q polarization
21- 26 F6.3 % Uu [-0.92/1.1] U band u polarization
28- 32 F5.3 % e_Uq [0.01/0.21] Error in Uq
34- 39 F6.3 % Bq [-2.64/-0.02] B band q polarization
41- 46 F6.3 % Bu [-1.13/1.07] B band u polarization
48- 52 F5.3 % e_Bq [0.01/0.12] Error in Bq
54- 59 F6.3 % Vq [-2.61/-0.02] V band q polarization
61- 66 F6.3 % Vu [-1.28/1.13] V band u polarization
68- 72 F5.3 % e_Vq [0.01/0.11] Error in Vq
74- 79 F6.3 % Rq [-2.49/0.16] R band q polarization
81- 86 F6.3 % Ru [-1.43/1.09] R band u polarization
88- 92 F5.3 % e_Rq [0.009/0.21] Error in Rq
94- 99 F6.3 % bq [-1.37/-0.16]? b band q polarization
101-106 F6.3 % bu [-1.13/0.48]? b band u polarization
108-112 F5.3 % e_bq [0.01/0.09]? Error in bq
114-121 F8.4 d HJDb [410/418]? Heliocentric Julian date of b band;
HJD-2440000 (1)
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Note (1): UBVR observations occurred simultaneously. Stromgren b filter
observations occurred at a different time, recorded in the
last column.
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 F7.3 d HJD [320/889] Heliocentric Julian date; HJD-2447000
9- 14 F6.3 % Uq [-0.12/0.68] U band q polarization
16- 20 F5.3 % e_Uq [0.003/0.31] Error in Uq
22- 27 F6.3 % Uu [-0.9/0.15] U band u polarization
29- 33 F5.3 % e_Uu [0.01/0.21] Error in Uu
35- 39 F5.3 % Bq [0.06/0.57] B band q polarization
41- 45 F5.3 % e_Bq [0.009/0.1] Error in Bq
47- 52 F6.3 % Bu [-0.46/0.05] B band u polarization
54- 58 F5.3 % e_Bu [0.006/0.13] Error in Bu
60- 64 F5.3 % Vq [0.03/0.47] V band q polarization
66- 70 F5.3 % e_Vq [0.008/0.1] Error in Vq
72- 77 F6.3 % Vu [-0.49/0.001] V band u polarization
79- 83 F5.3 % e_Vu [0.01/0.08] Error in Vu
85- 89 F5.3 % Rq [0.08/0.45] R band q polarization
91- 95 F5.3 % e_Rq [0.01/0.1] Error in Rq
97-102 F6.3 % Ru [-0.42/-0.03] R band u polarization
104-108 F5.3 % e_Ru [0.01/0.1] Error in Ru
110-115 F6.3 % Iq [-0.04/0.42] I band q polarization
117-121 F5.3 % e_Iq [0.006/0.08] Error in Iq
123-128 F6.3 % Iu [-0.37/-0.007] I band u polarization
130-134 F5.3 % e_Iu [0.01/0.15] Error in Iu
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Byte-by-byte Description of file: tablea3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 F7.4 d HJD [59/74] Heliocentric Julian date; HJD-2447700
9- 13 F5.3 % Uq [0.94/1.5] U band q polarization
15- 19 F5.3 % e_Uq [0.03/0.11] Error in Uq
21- 25 F5.3 % Uu [0.13/0.47] U band u polarization
27- 31 F5.3 % e_Uu [0.02/0.12] Error in Uu
33- 37 F5.3 % Bq [0.79/1.15] B band q polarization
39- 43 F5.3 % e_Bq [0.02/0.06] Error in Bq
45- 49 F5.3 % Bu [0.07/0.34] B band u polarization
51- 55 F5.3 % e_Bu [0.01/0.08] Error in Bu
57- 61 F5.3 % Vq [0.85/1.27] V band q polarization
63- 67 F5.3 % e_Vq [0.03/0.07] Error in Vq
69- 73 F5.3 % Vu [0.1/0.4] V band u polarization
75- 79 F5.3 % e_Vu [0.01/0.09] Error in Vu
81- 85 F5.3 % Rq [0.68/1] R band q polarization
87- 91 F5.3 % e_Rq [0.02/0.09] Error in Rq
93- 97 F5.3 % Ru [0.03/0.25] R band u polarization
99-103 F5.3 % e_Ru [0.01/0.09] Error in Ru
105-109 F5.3 % Iq [0.61/0.9] I band q polarization
111-115 F5.3 % e_Iq [0.01/0.08] Error in Iq
117-122 F6.3 % Iu [-0.06/0.24] I band u polarization
124-128 F5.3 % e_Iu [0.02/0.07] Error in Iu
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 06-Jul-2020