Measuring the orbital inclination of Z Andromedae from Rayleigh scattering

Abstract

The orbital inclination of the symbiotic prototype Z And has not been established yet. At present, two very different values are considered, i ~ 44 degrees and i >~ 73 degrees. The correct value of i is a key parameter in, for example, modeling the highly-collimated jets of Z And. The aim of this paper is to measure the orbital inclination of Z And. First, we derive the hydrogen column density (nH), which causes the Rayleigh scattering of the far-UV spectrum at the orbital phase phi = 0.961 plus/minus 0.018. Second, we calculate nH as a function of i and phi for the ionization structure during the quiescent phase. Third, we compare the nH(i,phi) models with the observed value. The most probable shaping of the HI/HII boundaries and the uncertainties in the orbital phase limit i of Z And to 59 -2/+3 degrees. Systematic errors given by using different wind velocity laws can increase i up to ~74 degrees. A high value of i is supported independently by the orbitally related variation in the far-UV continuum and the obscuration of the OI] 1641 A emission line around the inferior conjunction of the giant. The derived value of the inclination of the Z And orbital plane allows treating satellite components of H-alpha and H-beta emission lines as highly-collimated jets.

arXiv comment6 pages, 7 figures, accepted for Astronomy and Astrophysics

References in corpus (5)

• Disentangling the composite continuum of symbiotic binaries I. S-type systems
• A "Combination Nova" Outburst in Z Andromedae: Nuclear Shell Burning Triggered by a Disk Instability
• Transient jets in the symbiotic prototype Z Andromedae
• Discovery of the eclipse in the symbiotic binary Z Andromedae
• The O I] 1641A line as a probe of symbiotic star winds

Cited by in corpus (6)

• New outburst of the symbiotic nova AG Peg after 165 years
• Wind mass transfer in S-type symbiotic binaries II. Indication of wind focusing
• Disc instabilities and nova eruptions in symbiotic systems: RS Ophiuchi and Z Andromedae
• Wind asymmetry imprint in the UV light curves of the symbiotic binary SY Mus
• The emergence of a neutral wind region in the orbital plane of symbiotic binaries during their outbursts
• Rayleigh scattering from hydrogen atoms including resonances and high photon energies