Mathematics – Metric Geometry
Scientific paper
Jul 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...429..846s&link_type=abstract
The Astrophysical Journal, vol. 429, no. 2, pt. 1, p. 846-856
Mathematics
Metric Geometry
53
Astronomical Models, Axisymmetric Bodies, Blue Stars, Ejecta, H Alpha Line, Linear Polarization, Opacity, Stellar Envelopes, Stellar Evolution, Stellar Winds, Variations, Charge Coupled Devices, Electron Scattering, Polarimeters, Time Dependence, Visible Spectrum, Wing Profiles
Scientific paper
We present optical linear spectropolarimetry of the Luminous Blue Variable AG Carinae obtained after a recent visual brightness increase. The absence of He II lambda 4686 emission, together with the weakening of the He I spectrum and the appearance of Fe lines in the region around 5300 A, confirm that AG Car has started a new excursion across the HR diagram. The H alpha line profile exhibits very extended line wings that are polarized differently in both amount and position angle from either the continuum or the line core. The polarization changes across H alpha, together with variable continuum polarization, indicate the presence of intrinsic polarization. Coexistence of the line-wing polarization with extended flux-line wings evidences that both are formed by electron scattering in a dense wind. The position angle rotates across the line profiles, in a way that presently available models suggest is due to rotation and expansion of the scattering material. AG Car displays very large variations of its linear polarization with time, Delta P approximately 1.2%, indicating significant variations in envelope opacity. We find that the polarization varies along a preferred position angle of approximately 145 deg (with a scatter of +/- 10 deg) which we interpret as a symmetry axis of the stellar wind (with an ambiguity of 90 deg). This position angle is co-aligned with the major axis of the AG Car ring nebula and perpendicular to the AG Car jet. Our observations thus suggest that the axisymmetric geometry seen in the resolved circumstellar environment at various distances already exists within a few stellar radii of AG Car. From the H alpha polarization profile we deduce an interstellar polarization of Q = 0.31%, U = -1.15% at H alpha. The inferred interstellar polarization implies that the intrinsic polarization is not always of the same sign. This indicates either significant temporal changes in the envelope geometry, or it may arise from effects of multiple scattering in conjunction with density variations.
Clayton Geoffrey C.
Harries Tim J.
Hillier Desmond John
Howarth Ian D.
Schulte-Ladbeck Regina E.
No associations
LandOfFree
The axisymmetric stellar wind of AG Carinae does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The axisymmetric stellar wind of AG Carinae, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The axisymmetric stellar wind of AG Carinae will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1253205