Hires IUE Observations of the Peculiar Stars RX Puppis and R Aquarii
Abstract
The symbiotic variables R Aquarii and RX Puppis exhibit a variety of emission properties over a wide range of wavelengths that includes centimeter, IR, X-ray, optical as well as intense emission in the near and far-UV. They are regarded as prototypes for detailed investigation of the symbiotic phenomena, because the morphology discerned with high spatial radio continuum maps indicate jet, or collimated flow from these systems. We have undertaken a detailed study of these objects in order to determine the UV line and continuum emission properties of these systems in context with the radio morphology. Recently obtained IUE spectra of R Aqr (M7e+pec) indicate that the region of maximum UV line emission appears displaced relative to the suspected location of the Mira and hot subdwarf, which are surrounded in a compact HII region. This is indicated from LORES-SWP spectra by a systematic wavelength shift evident in most of the high excitation UV emission lines in the direction of the jet; the 10x20" aperture of IUE is centered at the radio position that corresponds to the HII region, and the position angle of the aperture is oriented so that the dispersion of the SWP-LORES camera is closely aligned with the axis by the radio emitting features which comprise the jet. When the large IUE entrance aperture is recentered at radio Feature-A (approximately 2.7 NE from the HIT region), the high excitation emission lines of C IV, He II, Si III] and C III] appear at their respective nominal wavelengths, providing further evidence that the compact HII region, which is the brightest component in 6-cm radio continuum maps, is not the primary source of high excitation UV line emission, as previously assumed. We propose collaborative NASA-ESA, HIRES-SWP observations of the central HII region surrounding R Aqr, enabling us to examine for the first time the line profile properties of strong high excitation resonance and intercombination emission lines for velocity and spatially extended structure with ~0.1A resolution. These observations may have direct application to more distant and spatially unresolved symbiotics. For example, the C IV emission doublet recently observed in HIRES-SWP spectra of the nebular jet (feature B) region in R Aqr, reveals multi-component structure, similar to that seen in RX Puppis. But recently obtained sub-arcsecond VLA observations of RX Puppis indicates it also possesses a jet, reminiscent of the R Aqr radio morphology, but smaller in scale owing to its greater distance. Collaborative (NASA-ESA) deep SWPHIRES exposures of RX Puppis are requested in order to properly expose the broad wings of the C IV doublet and other high excitation emission lines, for comparison with the line profile structure of the central HII region of R Aqr. Similarity of line profile structure may be generally indicative of collimated mass expulsion in a subset of symbiotic stars which are strong emitters at centimeter wavelengths, and which contain Mira-type variable.
- Publication:
-
IUE Proposal
- Pub Date:
- 1987
- Bibcode:
- 1987iue..prop.2814M