Astron. Astrophys. 363, 1029-1039 (2000)

4. Results - photometry

Fig. 7 shows the light curve derived from the slit magnitudes in the 1998 NTT run, folded by the orbital period after removing the nightly brightening tendency due to the pre-outburst stage. The scatter in the photometry is approximately 0.2 mag, but an eclipse with  mag depth is detected in the light curve. Details outside eclipse are not so clear, except a possible hump around photometric phase .

Fig. 7. The light curve by the slit photometry folded by the orbital period. The open squares, circles, and diamonds respectively represent the data of May 29, 30, and 31. The zero point of the photometric phase is based on the timing of the eclipse (HJD = 2450963.781).

The photometric sequence cannot be used to determine the orbital period due to the large scatter of the data. A timing of the eclipse is roughly estimated as HJD = 2450963.781(3) for the data of May 29, corresponding to . This ephemeris is consistent with the rotational disturbance seen around in the folded radial velocity curves. Fig. 8 displays the radial velocity variation of H around the eclipse on May 29; the data sets of 50  separation are used in order to emphasize timings of rotational disturbances, so note the best-fitted curve is based on the ephemeris given in Eq. (1). The figure indicates that the timing of the eclipse is just coincident with a disturbed point in the radial velocity, and shows the photometric minima shifted from .

Fig. 8. The radial velocity variation of a part of May 29 (the filled squares). The timings of the spectroscopic and photometric minima are indicated as the vertical dash-dotted and dotted lines, respectively. The long-dashed line represents the fitted sinusoid based on the ephemeris given in Eq. (1), and the horizontal short-dashed line represents the systemic velocity.

Fig. 9 shows the light curve of the 1999 Kyoto run folded at the orbital period; the bins contain about 30 data each after removing the systematic differences of magnitudes among the individual nights (a post-outburst phase around HJD = 2451311). Due to the low altitude of the object from the observatory, data points at large air mass were excluded. We obtained a photometric minimum at HJD = 2451298.236(2) (). The shape is similar to that of the slit photometry, showing an orbital hump at and an eclipse with  mag depth and orbital phase width. A possible secondary minimum may be seen around on the light curve.

Fig. 9. The photometric light curve of the 1999 Kyoto run folded on the orbital period. The zero point of the photometric phase is based on the timing of the eclipse.

© European Southern Observatory (ESO) 2000

Online publication: December 5, 2000
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