IUE observations of the peculiar star RX Puppis

Abstract

We have obtained the first high-dispersion observations of RX Pup in the wavelength region 1200-2000 A with the International Ultraviolet Explorer. RX Pup has been classified a symbiotic star and has been compared to slow novae as well as to 11 Carinae. The anomalies that we observed in high-excitation lines in RX Pup such as He II, 0 III], C III], C IV, and Si IIIl that show split line profiles, Doppler displaced multiple components, and possible inverse P Cygni profiles inN III] and N IV J suggest dynamic activity in circumstellar material that probably has the form of rings and/or gas streamers between the cool giant and the hot companion. The continuum observed by us in low dispersion is fairly flat in the wavelength region 1200-2000 A and rises toward longer wavelengths in the region 2000-3200 A. It cannot be due to a star earlier than AO II. Alternatively it may be from an accretion disk. We find electron densities in the line-emitting region in the range 10 9-10 11 em-3 , temperatures in the range 10,000-20,000 K, and linear sizes :S a few x 10 13 em. We find that the photoionizing radiation may be due to the presence of an unseen, hot subdwarf with most probable effective temperature in the range 75,000-90,000 K. Alternatively it may be due to an accretion disk around a secondary with boundary layer temperature-10 5 K. Short-range as well as long-range monitoring of this very interesting object in the far-UV would be very helpful in understanding the nature of its peculiar properties and the connection between slow novae and symbiotic stars.

The Ultraviolet Spectrum of RX Puppis

“…The 1548/1550 C IV intensity ratio has been observed to be always less than unity (Kafatos et al 1985). Typical velocity differences between individual components are 40 -50 km/s.…”

“…Kafatos, Michalitsianos and Feibelman 1982). Night to night v a r i a t i o n s in the Balmer l i n e i n t e n s i t i e s were found in 1975 (Swings and Klutz 1976).…”

“…High excitation l i n e s become present when the star becomes fainter (Allen and Wright 1987). In 1982 the UV emission lines became stronger (Kafatos et al 1985). The multicomponent structure of the C IV profiles seen with IUE is not unique: Recently, observations of the central H II region around R Aqr (Michalitsianos et al 1987) reveal similar structure as well as HM Sge (Mueller and Nussbaumer 1985).…”

“…There i s an indication of broad P-Cygni structure in the C IV profiles seen by the "International Ultraviolet Explorer" (IUE) although no d i r e c t detection of i t (Kafatos et a l . 1982;Kafatos, Michalitsianos and Fahey 1985). The far UV spectrum of RX Pup obtained with the IUE shows a number of prominent emission l ines and a weak continuum.…”

Modeling of C IV pumped fluorescence of Fe II in symbiotic stars

“…Values from 10 7 cm −3 (Whitelock et al 1984) derived by optical forbidden lines to 10 10 cm −3 (Kafatos et al 1982) derived from UV inter combination lines have been reported. The electron temperature in the fluorescence region is also difficult to estimate since the nebula consists of typically low temperature regions (the inner parts of the Mira shell) as well as regions of temperatures in excess of 15 000 K (Mikolajewska et al 1999).…”