J/A+A/670/A176 B, V and R band polarimetry of AO Cas (Abdul Qadir+, 2023)
High-precision broadband linear polarimetry of early-type binaries.
III. AO Cassiopeiae revisited.
Abdul Qadir Y., Berdyugin A.V., Piirola V., Sakanoi T., Kagitan M.
<Astron. Astrophys. 670, A176 (2023)>
=2023A&A...670A.176A 2023A&A...670A.176A (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, eclipsing ; Polarization ; Optical
Keywords: stars: individual: AO Cassiopeiae - polarization -
techniques: polarimetric - binaries close -
instrumentation: polarimteters - binaries: eclipsing
Abstract:
The fact that the O-type close binary star system AO∼Cassiopeiae
exhibits variable phase-locked linear polarization has been known
since the mid-1970s. In this work, we re-observe the polarization
arising from this system more than 50 years later to better estimate
the interstellar polarization and to independently derive the orbital
parameters, such as inclination, i, orientation, Ω, and the
direction of the rotation for the inner orbit from the phase-folded
polarization curves of the Stokes q and u parameters.
The Dipol-2 polarimeter was used to obtain linear polarization
measurements of AO Cassiopeiae in the B, V, and R passbands with the
T60 remotely controlled telescope at an unprecedented accuracy level
of ∼0.003%. We have obtained the first proper quantification of the
interstellar polarization in the direction heading towards AO Cas by
observing the polarization of three neighboring field stars. We
employed a Lomb-Scargle algorithm and detected a clear periodic signal
for the orbital period of AO Cas. The standard analytical method based
on a two-harmonics Fourier fit was used to obtain the inclination and
orientation of the binary orbit.
Our polarimetric data exhibited an unambiguous periodic signal at
1.76-days, thus confirming the orbital period of the binary system of
3.52-days. Most of the observed polarization is of interstellar
origin. The de-biased values of the orbital inclination are
i=63+2-3° and orientation of Ω=29° (209°)
±8°. The direction of the binary system rotation on the plane of
the sky is clockwise.
Description:
We observed AO Cas for a total of 39 nights, from October 26, 2020
until February 01, 2021, with the DiPol-2 polarimeter, attached to the
remotely controlled T60 telescope at Haleakala Observatory, Hawaii.
DiPol-2 uses two dichroic beam-splitters that split the incident light
beam into the B, V, and R passbands, which are simultaneously recorded
by three CCD cameras.
Objects:
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RA (2000) DE Designation(s)
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00 17 43.06 +51 25 59.1 AO Cas = HR 65
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
pol.dat 78 39 Polarization data of AO Cas
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See also:
J/A+A/591/A92 : BVR polarimetry of HD 48099 (Berdyugin+, 2016)
J/A+A/611/A69 : B,V and R band polarimetry of lambda Tau (Berdyugin+, 2018)
Byte-by-byte Description of file: pol.dat
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Bytes Format Units Label Explanations
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1- 12 F12.4 d JD Julian date
14- 20 F7.4 --- q(B) Stokes q in B-band
22- 27 F6.4 --- u(B) Stokes u in B-band
29- 34 F6.4 --- e_q(B) Error of q(B) and u(B)
36- 42 F7.4 --- q(V) Stokes q in V-band
44- 49 F6.4 --- u(V) Stokes u in V-band
51- 56 F6.4 --- e_q(V) Error of q(V) and u(V)
58- 64 F7.4 --- q(R) Stokes q in R-band
66- 71 F6.4 --- u(R) Stokes u in R-band
73- 78 F6.4 --- e_q(R) Error of q(R) and u(R)
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Acknowledgements:
Yasir Abdul Qadir, yasir.abdulqadir(at)utu.fi
References:
Berdyugin et al., Paper I 2016A&A...591A..92B 2016A&A...591A..92B, Cat. J/A+A/591/92
Berdyugin et al., Paper II 2018A&A...611A..69B 2018A&A...611A..69B, Cat. J/A+A/611/69
(End) Patricia Vannier [CDS] 23-Jan-2023