Bibcode
Schmid, H. M.; Corradi, R.; Krautter, J.; Schild, H.
Bibliographical reference
Astronomy and Astrophysics, v.355, p.261-270 (2000)
Advertised on:
3
2000
Journal
Citations
27
Refereed citations
23
Description
We present the first spectropolarimetric observations of the symbiotic
nova HM Sge. We first note that marked spectral changes occurred: in the
near IR the spectrum of the Mira in the system has clearly appeared. The
nebular emission line spectrum remains largely unchanged but we detect
for the first time the Raman line at lambda 6825. These changes indicate
that the dust content in HM Sge is rapidly decreasing and that the dust
obscuration period which began in 1985 has come to an end. In terms of
polarization we find that the red giant spectrum is intrinsically
polarized at the 0.5 % level and the polarization signal is structured
across the TiO absorption bands. The Raman scattered O vi line at lambda
6825 shows a polarization of 3.4 % at an angle of 33 deg. The
behaviour of the polarization angle across the Raman line strongly
indicates that an axisymmetric O vi-H i scattering geometry prevails.
The distribution of the neutral hydrogen in the inner binary system does
not seem to be strongly perturbed by binary motion. We conclude that the
present binary axis is orientated at a position angle of ~ 123
deg. The deduced orientation of the binary axis of HM Sge is
parallel or perpendicular to distinct geometric features of the
surrounding nebulosity. This indicates that the orientation of the
binary system is of prime importance for the understanding of the
nebular structure. Based on observations taken with the 4.2m William
Herschel Telescope at La Palma and the 2.3m ANU Telescope at Siding
Spring.