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Astron. Astrophys. 363, 671-674 (2000)

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1. Introduction

RX Pup (HD 69190) is a symbiotic binary system containing a long-period Mira variable with P[FORMULA]580 days (Feast et al. 1977; Whitelock et al. 1983) and a white dwarf companion. Recently, Mikolajewska et al. (1999, hereafter M99) have presented a thorough study of the photometric and spectroscopic properties of RX Pup aimed at determining the basic parameters of the system. They concluded that the the companion of the Mira is a hot [FORMULA]0.8 [FORMULA] white dwarf that underwent a nova-like eruption around 1894, as well as a more recent one during the last three decades. During this last eruption, the white dwarf passed through a high luminosity phase lasting for a dozen years (1975-1988), moving toward high temperatures (up to [FORMULA]120000 K), and then turned down in the Herzprung-Russell diagram toward lower luminosities. During the high luminosity phase, accretion onto the white dwarf from the Mira wind (which is the underlying cause of the nova-like outbursts) was prevented by a strong stellar wind from the white dwarf. The velocity and mass loss rate of this fast wind were estimated by M99 to be of [FORMULA]140 km s-1 and [FORMULA]10[FORMULA][FORMULA] yr-1, respectively.

These energetic outflows that are produced during the active phases of the hot companions of symbiotic Miras are expected to interact with the relatively dense, slowly expanding circumstellar medium (note that during quiescence only 1[FORMULA] or less of the Mira wind is accreted onto the white dwarfs, cf. M99 and Corradi et al. 1999b). This interaction, together with the photoionisation from the hot star, gives rise to the complex, ionized nebulae which are observed around a significant fraction of symbiotic Miras (Corradi et al. 1999a). These nebulae contain important information about the geometry, dynamics, and history of the mass loss from symbiotic stars over the last hundreds or even few thousand years. In some cases, (spectro)polarimetric observations also allow us to derive the geometrical orientation of the unresolved central stars, and thus to have the basic information of the orientation of the outflow with respect to the binary system (e.g. Schmid et al. 2000).

In the case of RX Pup, extended nebular emission ([FORMULA]1") was found at radio wavelengths at 6 cm and 2 cm (Hollis et al. 1989), as well as in the optical by means of a coronographic, ground-based [NII ] image after subtraction of the unresolved core emission of the system (Paresce 1990, hereafter P90). The [NII ] image revealed an elongated structure extending toward P.A.=[FORMULA]o up to about 3".7 from the centre, which was interpreted by P90 as being a one-sided jet similar to the one of the other symbiotic Mira R Aqr (Hollis & Koupelis 2000and references therein). In this paper, we present long-slit echelle spectra of RX Pup aimed at obtaining further information about the optically extended outflow discovered by P90. Data and results are described in the next sections.

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© European Southern Observatory (ESO) 2000

Online publication: December 11, 2000