J/MNRAS/464/1936 V356 Sgr optical polarization (Lomax+, 2017)
The complex circumstellar and circumbinary environment of V356 Sgr.
Lomax J.R., Fullard A.G., Malatesta M.A., Babler B., Bednarski D.,
Berdis J.R., Bjorkman K.S., Bjorkman J.E., Carciofi A.C., Davidson Jr J.W.,
Keil M., Meade M.R., Nordsieck K., Scheffler M., Hoffman J.L.,
Wisniewski J.P.
<Mon. Not. R. Astron. Soc. 464, 1936-1947 (2017)>
=2017MNRAS.464.1936L 2017MNRAS.464.1936L (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Polarization
Keywords: polarization - binaries: eclipsing - circumstellar matter -
stars: massive - stars: individual: V356 Sgr
Abstract:
We analyse 45 spectropolarimetric observations of the eclipsing,
interacting binary star V356 Sgr, obtained over a period of ∼21yr,
to characterize the geometry of the system's circumstellar material.
After removing interstellar polarization from these data, we find that
the system exhibits a large intrinsic polarization signature arising
from electron scattering. In addition, the lack of repeatable eclipses
in the polarization phase curves indicates the presence of a
substantial pool of scatterers not occulted by either star. We suggest
that these scatterers form either a circumbinary disc coplanar with
the gainer's accretion disc or an elongated structure perpendicular to
the orbital plane of V356 Sgr, possibly formed by bipolar outflows. We
also observe small-scale, cycle-to-cycle variations in the magnitude
of intrinsic polarization at individual phases, which we interpret as
evidence of variability in the amount of scattering material present
within and around the system. This may indicate a mass-transfer or
mass-loss rate that varies on the time-scale of the system's orbital
period. Finally, we compare the basic polarimetric properties of
V356 Sgr with those of the well-studied β Lyr system; the
significant differences observed between the two systems suggest
diversity in the basic circumstellar geometry of Roche lobe overflow
systems.
Description:
Total and intrinsic optical polarization of the V356 Sgr system.
Observations were taken with the indicated telescope and instrument
setup, and then convolved with synthetic Johnson-Cousins broadband
filters.
Objects:
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RA (2000) DE Designation(s)
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18 47 52.33 -20 16 28.2 V356 Sgr = HD 173787
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 98 148 Total optical polarization
table3.dat 53 148 Intrinsic optical Polarization
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 20 A20 --- Inst Instrument
22- 31 F10.2 d JD Julian Date
33- 43 A11 "date" Obs.date Civil Date
45 A1 --- Filt [BVRI] Filter
47- 53 F7.4 % Q Q Stokes parameter
55- 60 F6.4 % U U Stokes parameter
62- 67 F6.4 % i_Q Internal error on Q and U
69- 74 F6.4 % e_Q Systematic error on Q and U
75- 80 F6.4 % Pol Percentage polarization in Filter band
82- 86 F5.2 deg PA Position angle of polarisation in Filter band
88- 92 F5.3 deg e_PA Position Angle error
94- 98 F5.3 --- Phase Phase
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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- 10 F10.2 d JD Julian Date
12- 22 A11 "date" Obs.date Civil Date
24 A1 --- Filt [BVRI] Filter
26- 30 F5.3 % Pol Polarization
32- 36 F5.3 % e_Pol Polarization error
38- 42 F5.2 deg PA Position angle
44- 47 F4.2 deg e_PA Position angle error
49- 53 F5.3 --- Phase Phase
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Acknowledgements:
Jamie R. Lomax, jrlomax(at)uw.edu
(End) Jamie R, Lomax [Univ. Washington], Patricia Vannier [CDS] 22-Sep-2016