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Astron. Astrophys. 349, 169-176 (1999)

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2. Observations

2.1. Optical high resolution spectra of SY Mus

SY Mus was observed with the Coudé échelle spectrograph (CES) fed by the 1.4 m Coudé auxiliary telescope (CAT) at the European Southern Observatory. The spectra have a resolution of [FORMULA], and cover [FORMULA] Å. The spectra are centered at 4363 Å, 5007 Å, 6563 Å, 6825 Å , or 7005 Å . In these settings M-giants have numerous absorption lines. Radial velocities (RV) of the M-star in SY Mus were determined by cross correlation with the radial velocity standard HR 4763 ([FORMULA], Foster & Wall 1998). The radial velocities are given in Table 1. Measurements during the same observing nights have been averaged. This results in a total of 30 data points. We combine our measurements with the RV-data in Table 1 of Schmutz et al. (1994).


Table 1. Radial velocity data of SY Mus. Given are the Julian date, the orbital phase according to Eq. 1 and the radial velocity of the M-giant.

2.2. IUE low resolution spectra of SY Mus

In the last IUE observing cycle we covered with the key program SI067, the egress phase of SY Mus with the goal of deriving the velocity law for the late giant in the system. Including these observations, the final IUE archive contains 69 short wavelength, low resolution spectra of SY Mus. In this paper we analyze 44 SWP low resolution spectra with a signal to noise ratio better than 4 at [FORMULA].

Short-ward of [FORMULA] the hot component dominates the continuum at all orbital phases. We measured the continuum flux at the two wavelengths [FORMULA] and [FORMULA], which are free from strong emission lines. The values are listed in Table 2.


Table 2. IUE low resolution short wavelength camera spectra of SY Mus. Given are the orbital phase [FORMULA] according to Eq. 1, the Julian date, the SWP image number, and continuum fluxes at 1325 Å and 1600 Å in units of 10-13 erg cm-2 s- 1 Å-1.

2.3. HST UV spectra of RW Hya

The eclipsing symbiotic binary system RW Hya has been observed during three visits with the Goddard High Resolution Spectrograph (GHRS) on board HST in cycles 5 and 6. We used the gratings G140L and G140M which provide resolutions of [FORMULA] and [FORMULA], respectively. In Table 3 we list the observing dates and exposure times of the GHRS observations. The observations on JD 2 450 261 were during eclipse of the hot object by the red giant, the observations on JD 2 450 286 were during egress. The orbital phases are according to the ephemeris of Schild et al. (1996) and Kenyon & Mikolajewska (1995).


Table 3. HST GHRS observing log of RW Hya. Exposure times are given in seconds. Orbital phases are according to the ephemeris of Schild et al. (1996)

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© European Southern Observatory (ESO) 1999

Online publication: August 25, 1999