1. PG 1618 was also observed with the CCD camera of the 1.23 m telescope at the German Spanish Astronomical Center, Calar Alto. The variability reported by Schuh et al. (2000) from a preliminary data reduction, however, could not be confirmed in the final analysis. Due to the smaller telescope and the poor weather conditions, the detection limit was much lower compared to the NOT data sets; therefore those results will not be used here.
2. The moving aperture photometry (MAP) technique computes the centre of the target in each frame and recenters the aperture correspondingly. This corrects for small tracking errors, allowing to use much smaller apertures, between 2.6 and 3.5 arcsec in our case.
3. The differences are even larger if we consider that in Fig. 7 the flux of the sdB star only is used. Thus the amplitudes of Fig. 7 should be compared with those reported in Table 3, where the contribution of the F3 star has been excluded.
4. Depending on the values of l and m, the (unprojected) rotational velocity would be included between a minimum of 40 Km/s (l=2,m=4, quite unlikely) and a maximum of 260 Km/s (l=1,m=1).
© European Southern Observatory (ESO) 2000
Online publication: July 13, 2000