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Astron. Astrophys. 358, 600-604 (2000)

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3. Photometry

Our most extensive photometry is from 1997 June, with the 1.3 m McGraw-Hill telescope at MDM and a Tektronix 10242 CCD direct camera. Photometry obtained on two nights referred to Landolt (1992) standards yielded the magnitude sequence in the caption to Fig. 1. Although all our observations of the source were in the V passband, fits to the standard star magnitudes showed that the color term for V was very small. On 1997 June 21 UT, we found the cataclysmic at [FORMULA] in a set of eight 1-min exposure; a longer sequence of 4-min exposures obtained 1997 June 22 yielded an average [FORMULA]. The June 22 observations extended for almost exactly one orbital period, to search for an eclipse. Fig. 2 shows the result of differential photometry. There is no eclipse evident, but the star does show small but significant irregular variability compared to a check star.

[FIGURE] Fig. 2. Differential photometry of the cataclysmic binary and a check star. Magnitudes are referred to Star 6 ([FORMULA]). The horizontal bar indicates the orbital period

We obtained a single 120 s direct CCD picture with the 1.3 m telescope on 1994 May 1.50, contemporaneous with the discovery and initial observations. This showed the star at [FORMULA].

Magnitudes can also be inferred from the continuum levels of the spectra (discussed below), though the small slits used limit the accuracy to [FORMULA] mag. The mean spectrum observed 1994 May 2.35 UT implies [FORMULA], consistent with the more reliable magnitude measured the previous night. However, the long series of observations obtained 1997 June 29 - July 2, about a week after the extensive photometry, show the star considerably fainter, near [FORMULA] on average. The true magnitude was probably somewhat brighter, because poor seeing marred many of the observations, but it is likely that it was at least as faint as [FORMULA].

In summary, the cataclysmic has a range from [FORMULA] down to [FORMULA]. We have no information on the variability beyond this, but the fading on a 1-week time-scale observed 1997 June/July suggests a dwarf nova declining from outburst.

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© European Southern Observatory (ESO) 2000

Online publication: June 8, 2000