The linear polarisation of southern bright stars measured at the parts-per-million level

Cotton, Daniel V., Bailey, Jeremy, Kedziora-Chudczer, Lucyna, Bott, Kimberly, Lucas, P.W., Hough, J. and Marshall, Jonathan P. (2016) The linear polarisation of southern bright stars measured at the parts-per-million level. Monthly Notices of the Royal Astronomical Society (MNRAS), 455 (2). pp. 1607-1628. ISSN 0035-8711
Copy

We report observations of the linear polarisation of a sample of 50 nearby southern bright stars measured to a median sensitivity of ~4.4 x 10^{-6}. We find larger polarisations and more highly polarised stars than in the previous PlanetPol survey of northern bright stars. This is attributed to a dustier interstellar medium in the mid-plane of the Galaxy, together with a population containing more B-type stars leading to more intrinsically polarised stars, as well as using a wavelength more sensitive to intrinsic polarisation in late-type giants. Significant polarisation had been identified for only six stars in the survey group previously, whereas we are now able to deduce intrinsic polarigenic mechanisms for more than twenty. The four most highly polarised stars in the sample are the four classical Be stars (alpha Eri, alpha Col, eta Cen and alpha Ara). For the three of these objects resolved by interferometry, the position angles are consistent with the orientation of the circumstellar disc determined. We find significant intrinsic polarisation in most B stars in the sample; amongst these are a number of close binaries and an unusual binary debris disk system. However these circumstances do not account for the high polarisations of all the B stars in the sample and other polarigenic mechanisms are explored. Intrinsic polarisation is also apparent in several late type giants which can be attributed to either close, hot circumstellar dust or bright spots in the photosphere of these stars. Aside from a handful of notable debris disk systems, the majority of A to K type stars show polarisation levels consistent with interstellar polarisation.

visibility_off picture_as_pdf

picture_as_pdf
hippi_aph.pdf
subject
Draft Version
lock
Restricted to Repository staff only

Request Copy
picture_as_pdf

Submitted Version


Atom BibTeX OpenURL ContextObject in Span OpenURL ContextObject Dublin Core MPEG-21 DIDL Data Cite XML EndNote HTML Citation METS MODS RIOXX2 XML Reference Manager Refer ASCII Citation
Export

Downloads