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Up: Identification of DQ Serpentis

1. Introduction

Symbiotic stars are long orbital period interacting binaries consisting of a late-type (G-M) giant which sheds material via stellar wind or Roche lobe overflow onto a more compact and hotter companion. The hot star provides an intense ultraviolet radiation field which ionizes a portion of the surrounding nebula, giving rise to emission lines like HI, HeI, HeII and [OIII] seen in these variables, while characteristics like strong red continuum, TiO and VO absorption bands, absorption lines of neutral and singly ionized metals are associated with the late-type star. The compact object in symbiotic stars is in most cases a white dwarf, which can derive its high luminosity and temperature by releases of potential energy in an accretion disk or as result of burning of hydrogen being accreted by the white dwarf or even from the cooling of an object resembling a nucleus of a planetary nebula. Low mass main sequence stars with an accretion disk can also occur as the ionizing source in such systems. For more details about the symbiotic stars see, e.g., Friedjung & Viotti (1982); Kenyon (1986) and Mikotex2html_wrap942 ajewska et al. (1988).

Table 1: Log of the spectroscopic observations

In a previous paper (Cieslinski et al. 1994) we presented observations of 6 symbiotic star candidates. In this paper we describe observations of two additional variables that we suggest as newly identified symbiotic stars. They show emission lines of HI, [OIII] and HeII tex2html_wrap_inline9064686, characteristics of this class of variables.

Figure 1: Spectra of DQ Ser (a, b, c, d) and DT Ser (e, f). The fluxes are in units of 10tex2html_wrap_inline908 erg cmtex2html_wrap_inline910 stex2html_wrap_inline912 Åtex2html_wrap_inline914

Table 2: tex2html_wrap_inline916 photometry

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