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Astron. Astrophys. 318, L9-L12 (1997)

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2. Ultraviolet and optical observations

A K0 star (GSC 00757-01608) was tentatively associated with a new EUV source (EUVE J0702+129, Bowyer et al. 1996; 2RE J0702+125, Pye et al. 1995). GSC 00757-01608 is, in fact, a double star composed of a bright K0 star and a K4 V star a few arcseconds to the NNE and 3:m5 fainter. The source of EUV emission was presumed to lie with the K0 star, and Bowyer et al. estimated count rates of [FORMULA], and [FORMULA]. Pye et al. estimated count rates of [FORMULA], and [FORMULA]. IUE spectra of the bright star ([FORMULA], from GSC) were obtained by M. Garcia-Vargas (Vilspa service observations) on 1995 November 11 (Table 1). The large aperture and low dispersion gratings were used; the short wavelength spectrum (swp56186llg) is unfortunately saturated between 1234 and 1412 Å. A second exposure could not be scheduled. Two long wavelength spectra (lwp31688llg, lwp31689llg) were acquired; the first exposure shows a spurious feature near 3120 Å and was discarded. The spectra were processed with the standard "NEWSIPS" reduction (Nichols & Linsky 1996).


Table 1. Far ultraviolet and optical observation log.

Following the discovery of a white dwarf companion to the K0 star in EUVE J0702+129, we monitered the system at Lick Observatory using the coudé auxiliary telescope (CAT) and the Hamilton echelle spectrograph (Vogt 1987) in 1995 November and December, and 1996 October, November, and December (Table 1). We used a [FORMULA] CCD binned [FORMULA] with a dispersion of [FORMULA] at Ca H&K and [FORMULA] at H [FORMULA] ; the spectral resolution is [FORMULA]. We then observed the K0 star with the Michigan-Dartmouth-MIT 2.4m telescope on 1996 January 6. We used the Mark III spectrograph and a Tek [FORMULA] CCD with a wavelength coverage of 3600-6000 Å at 5-6 Å resolution. The combined optical and ultraviolet spectrum is a composite of a K0 star and a hot DA white dwarf star (Fig. 1).

[FIGURE] Fig. 1. The K0+DA binary EUVE J0702+129 between [FORMULA] and 5850 Å, and a representative DA white dwarf synthetic spectrum.
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© European Southern Observatory (ESO) 1997

Online publication: July 8, 1998