J/A+A/591/A92 BVR polarimetry of HD 48099 (Berdyugin+, 2016)
High-precision broad-band linear polarimetry of early-type binaries:
I. Discovery of variable, phase-locked polarization in HD 48099.
Berdyugin A., Piirola V., Sadegi S., Tsygankov S., Sakanoi T., Kagitani M.,
Yoneda M., Okano S., Poutanen J.
<Astron. Astrophys. 591, A92 (2016)>
=2016A&A...591A..92B 2016A&A...591A..92B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, B-type ; Polarization
Keywords: techniques: polarimetric - binaries: close - stars: early-type
Abstract:
We investigate the structure of the O-type binary system HD 48099 by
measuring linear polarization that arises due to light scattering
process. High-precision polarimetry provides independent estimates of
the orbital parameters and gives important information on the
properties of the system. Linear polarization measurements of HD 48099
in the B, V and R passbands with the high-precision Dipol-2
polarimeter have been carried out. The data have been obtained with
the 60cm KVA (Observatory Roque de los Muchachos, La Palma, Spain) and
T60 (Haleakala, Hawaii, USA) remotely controlled telescopes during 31
observing nights.Polarimetry in the optical wavelengths has been
complemented by observations in the X-rays with the SWIFT space
observatory. Optical polarimetry revealed small intrinsic polarization
in HD 48099 with 0.1% peak to peak variation over the orbital period
of 3.08d. The variability pattern is typical for binary systems,
showing strong second harmonic of the orbital period. We apply our
model code for the electron scattering in the circumstellar matter to
put constraints on the system geometry. A good model fit is obtained
for scattering of light on a cloud produced by the colliding stellar
winds. The geometry of the cloud, with a broad distribution of
scattering particles away from the orbital plane, helps in
constraining the (low) orbital inclination. We derive from the
polarization data the inclination i=17°±2° and the longitude
of the ascending node Omega=82°±1° of the binary orbit. The
available X-ray data provide additional evidence for the existence of
the colliding stellar winds in the system. Another possible source of
the polarized light could be scattering from the stellar photospheres.
The models with circumstellar envelopes, or matter confined to the
orbital plane, do not provide good constraints on the low inclination,
better than i≤27°, as is already suggested by the absence of
eclipses.
Description:
Normalized Stokes parameters of linear polarization (q, u) measured in
the B, V and R pass-bands are presented with their errors. For each
measurement the heliocentric Julian date, phase of the orbital period
at the time of the observation and the name of the telescope are
given.
Objects:
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RA (2000) DE Designation(s)
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06 41 59.23 +06 20 43.5 HD 48099 = HR 2467
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 96 31 Linear polarization data for HD 48099
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 12 F12.4 d JD Heliocentric Julian Date
15- 20 F6.4 % q(B) Stokes q in the B-band
23- 28 F6.4 % u(B) Stokes u in the B-band
31- 36 F6.4 % e_q(B) Error of measurement in the B-band
39- 44 F6.4 % q(V) Stokes q in the V-band
47- 52 F6.4 % u(V) Stokes u in the V-band
55- 60 F6.4 % e_q(V) Error of measurement in the V-band
63- 68 F6.4 % q(R) Stokes q in the R-band
71- 76 F6.4 % u(R) Stokes q in the R-band
79- 84 F6.4 % e_q(R) Error of measurement in the R-band
87- 92 F6.4 --- Phase Phase of the orbit (1)
94- 96 A3 --- Tel Name of the telescope
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Note (1): Ephemeris To = HJD2452649.661 + 3.07806E(days) is taken from the
paper by Mahy et al. (2010ApJ...708.1537M 2010ApJ...708.1537M)
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Acknowledgements:
Andrei Berdyugin, andber(at)utu.fi
(End) Andrei Berdyugin [Univ. Turku Finland], Patricia Vannier [CDS] 13-May-2016