A1 Vertaisarvioitu alkuperäisartikkeli tieteellisessä lehdessä
A Multiwavelength Search for Intrinsic Linear Polarization in Wolf-Rayet Winds
Tekijät: Fullard AG, St-Louis N, Moffat AFJ, Piirola VE, Manset N, Hoffman JL
Kustantaja: IOP PUBLISHING LTD
Julkaisuvuosi: 2020
Journal: The Astronomical Journal
Tietokannassa oleva lehden nimi: ASTRONOMICAL JOURNAL
Lehden akronyymi: ASTRON J
Artikkelin numero: ARTN 214
Vuosikerta: 159
Numero: 5
Sivujen määrä: 15
ISSN: 0004-6256
eISSN: 1538-3881
DOI: https://doi.org/10.3847/1538-3881/ab8293
Verkko-osoite: https://iopscience.iop.org/article/10.3847/1538-3881/ab8293
Tiivistelmä
Wolf-Rayet 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 similar to 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 lambda 4600-4700 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.
Wolf-Rayet 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 similar to 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 lambda 4600-4700 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.
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