Open AccessThe polarimetric nature of HD 108
Author(s) -
Fox Geoffrey K.,
Hines Dean C.
Publication year - 1998
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1998.01296.x
Subject(s) - physics , supergiant , astrophysics , stars , position angle , polarimetry , stellar rotation , giant star , wolf–rayet star , astronomy , polarization (electrochemistry) , stellar evolution , scattering , galaxy , chemistry , optics
V ‐band polarimetric observations of HD 108 were obtained during 1994 August and September. This is the first time that the temporal polarimetric variability of this star has been investigated. Its percentage polarization and position angle vary randomly, and no evidence of its proposed binary nature is detected. The random variability is consistent with that seen for previously observed Wolf–Rayet stars and OB supergiants. Nightly variations do show some systematic behaviour consistent with the blob ejection model of Underhill & Fehey (1984). From the data it is estimated that the mass‐loss rate resulting from blobs is ∼1‐10 −7 M⊙ yr −1 . The total mass‐loss rate of the star is estimated to be ∼1‐10 −5 M⊙ yr −1 . The stellar rotation rate is estimated to be V rot ∼400 km s −1 with an inclination of i <20c. The data are also interpreted in terms of perturbations occurring in an equatorial disc plus bipolar jets viewed equatorially (Underhill 1994). It is found that the perturbation mass‐loss rate is about ∼3‐10 −7 M⊙ yr −1 , giving a total mass‐loss rate for the star of 13‐10 −5 M⊙ yr −1 . Both models are consistent with HD 108 being an OB supergiant or of the class Ofpe/WR9.