2 45 Leo

Provin (1953) found the sharp-lined star (v sin i = 10 km s^-1, Abt & Morrell 1995) 45 Leo (= HR 4101 = HD 90569 = CX Leo) to be photometrically constant, while Burke et al. (1970) thought it was probably variable. Winzer (1974) discovered it was a low amplitude photometric variable with a period of 1.4450 days, a result confirmed by Wolff & Morrison (1975), but not Bonsack (1976). We are looking at a polar region. Leroy (1995) finds its polarization of 0.12% is due in part to interstellar polarization. It is not a star he expects to be usefully studied via broadband polarimetry.

We obtained 60 and 49 differential uvby observations of 45 Leo during the 1995-96 and 1996-97 observing seasons, respectively. As 45 Leo is not particularly variable longward of the Balmer jump, we studied the u values and found that the most likely period was 1.4438 days. To bring the U values of Winzer (1974) appropriately rezeroed into best agreement with our data resulted in a slight increase in the period. We also had to adjust the zero point of Winzer's ephemeris. Thus

HJD(u$_{\max}$) = 2441460.954 $\pm$ 0.002 + (1.443820 $\pm$ 0.000005) E.

If Wolff & Morrison (1975) had published their data in tabular form, we might have been able to reduce our errors. The amplitudes of variability are 0.042 mag for u, 0.010 mag for b, and 0.005 mag for v and y (Fig. 1). Both u and b vary in phase in a single wave. The marginal variability of v and y are probably also in phase.

  

Figure 1: Photometry of 45 Leo plotted with the ephemeris HJD(u$_{\max}$) = 2441460.954 + 1.443820 E. The FCAPT uvby values are indicated by + signs while Winzer's U and V values as rezeroed to the u and y scales, respectively, are closed circles