J/A+A/677/A75 B, V and R band polarimetry of DH Cep (Abdul Qadir+, 2023)
High-precision broadband linear polarimetry of early-type binaries.
IV. The DH Cephei binary system in the open cluster of NGC 7380.
Abdul Qadir Y., Berdyugin A.V., Piirola V., Sakanoi T., Kagitan M.
<Astron. Astrophys. 677, A75 (2023)>
=2023A&A...677A..75A 2023A&A...677A..75A (SIMBAD/NED BibCode)
ADC_Keywords: Binaries, eclipsing ; Polarization ; Optical
Keywords: stars: individual: DH Cephei - polarization -
techniques: polarimetric - binaries: close -
instrumentation: polarimeters
Abstract:
DH Cephei is a well known massive O+O-type binary system on the
northern sky, situated at the center of young open cluster NGC 7380.
Our high-precision multi-band polarimetry has clearly revealed that
variations of linear polarizations in this system are synchronous
with the phase of the orbital period. We have used the observed
variations of Stokes parameters q and u to derive the orbital
inclination i, orientation Ω, and the direction of rotation.
Moreover, in order to get a sense of interstellar polarization in the
vicinity of DH Cep, we have observed polarization arising from the
neighboring stars in the cluster.
We used the Dipol-2 polarimeter in combination with the remotely
controlled 60cm Tohoku T60 telescope, to obtain linear polarization
measurements of DH Cep in the B, V, and R passbands at the accuracy
level of ∼0.003. To obtain an estimation of interstellar polarization
of DH Cep, we have observed more than a dozen field stars that have
been identified as members of NGC 7380 and are in the close proximity
of DH∼Cep. Lomb-Scargle period search has been applied to the acquired
polarization data to reveal the dominating frequency in polarization
variations. We also used a standard analytical method based on a
two-harmonics Fourier fit to derive the inclination, orientation, and
the direction of rotation of the binary orbit.
The variations of Stokes parameters in all three B, V, and R
passbands clearly exhibit an unambiguous periodic signal at 1.055d
with the amplitude of variations ∼0.2% which corresponds to
half of the known orbital period of 2.11d. This type of polarization
variability is expected for a binary system with light scattering
material distributed symmetrically with respect to the orbital plane.
In addition to the regular polarization variability, there is a
non-periodic component, strongest in the B passband. We obtained in
the V passband our most reliable values for the orbital inclination
i=46°+11°/-46° and the orientation of the
orbit on the sky Ω=105°±55°, with 1σ
confidence intervals. Using our best estimate of i and the
polarimetric amplitude in the V passband, we estimated that the
mass-loss of the system is ∼3.4x10-7M☉/yr.
The direction of the binary system rotation on the plane of the sky is
clockwise. Our polarimetric observations of neighboring stars of DH
Cep in NGC 7380 reveal that the polarization of the cluster stars is
most likely due to aligned interstellar dust in the foreground.
Description:
Polarimetric data of DH Cep: MJD, Stokes q in B passband, Stokes u in
B Passband, error in B passband, Stokes q in V passband, Stokes u in V
Passband, error in V passband, Stokes q in R passband, Stokes u in R
Passband, error in R passband.
Objects:
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RA (2000) DE Designation(s)
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22 46 54.11 +58 05 03.5 DH Cep = BD+57 2607
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
pol_data.dat 94 69 Polarization data of DH Cep
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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)
J/A+A/670/A176 : B, V and R band polarimetry of AO Cas (Abdul Qadir+, 2023)
Byte-by-byte Description of file: pol_data.dat
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Bytes Format Units Label Explanations
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1- 12 F12.4 d JD Julian date
14- 19 F6.4 --- Phase Phase
21- 26 F6.4 --- q(B) Stokes q in B-band
28- 34 F7.4 --- u(B) Stokes u in B-band
36- 44 E9.5 --- e_q(B) Error of q(B) and u(B)
46- 51 F6.4 --- q(V) ? Stokes q in V-band
53- 59 F7.4 --- u(V) ? Stokes u in V-band
61- 69 E9.5 --- e_q(V) ? Error of q(V) and u(V)
71- 76 F6.4 --- q(R) Stokes q in R-band
78- 84 F7.4 --- u(R) Stokes u in R-band
86- 94 E9.5 --- 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
Abdul Qadir et al., Paper III 2023A&A...670A.176A 2023A&A...670A.176A, Cat. J/A+A/670/A176
(End) Yasir Abdul Qadir [UTU, Finland], Patricia Vannier [CDS] 19-Jul-2023