2 HD 35298

North (1984) derived a period of 1.85336 $\pm$ 0.00116 days for the Helium weak star HD 35298 (= V1156 Ori = BD +1$^{\circ}$ 996), a member of the Ori OB1 association. This star exhibits a double-wave light curve with all colors varying in phase. The amplitude is as large as 0.07 mag in the Geneva photometric system. Borra (1981) measured the magnetic field with essentially this period.

We have 100 differential uvby observations, 56 from the 1995-96 and 44 from the 1996-97 observing seasons. A periodogram analysis resulted in a period close to one-half of North's period. But when we plotted the observations, there were two values for each phase indicating that the period was twice that. To have North's V values properly rezeroed best overlay our y values we had to adjust his period slightly. The zero epoch is better taken for maximum light in u. Thus
HJD (u$_{\rm max}$) = 2444973.886 $\pm$ 0.006 + (1.85457 $\pm$ 0.00001) E.

Figure 1 shows our FCAPT photometry (+ signs) and North's V values (solid diamonds) on our y magnitude scale plotted with our ephemeris. The amplitudes are 0.08 mag for u, 0.05 mag for v and b, and 0.037 mag for y. The light curves are in phase with two minima and a primary and secondary maxima. Some light curves especially u and v show additional structure as the star begins the primary minimum. The relative depths of the two minima are more discrepant for u than for v, b, and y. We are probably seeing most of the photosphere including both polar regions during the cycle. North's U light curve has an amplitude similar to ours, but some of the details near phase 0.5 are not seen probably due to a lesser number of values. Likewise his B light curve is similar to our b.

  

Figure 1: Photometry of HD 35298 plotted using this paper's ephemeris of HJD ($u_{\rm max}$) = 2444973. 886 + 1.85457 E. The FCAPT uvby values are indicated by + signs and North's V magnitudes rezeroed to our y magnitudes as closed diamonds