JD (positive magnetic maximum) = 2435997.50 + 5.07622 0.0004 E
which is consistent with the period found by Leroy (1995) and also takes into account observations taken by Babcock (1958). Photometric variability was found by Wolff (1975) using Strömgren photometry.
The FCAPT obtained 35, 46, and 31 good sets of differential Strömgren values during the 1995-96, 1996-97, and 1997-98 observing seasons, respectively. Their Scargle periodograms suggests a period close to 5.076 days or its alias. When this data and that of Wolff (appropriately rezeroed) are plotted with the ephemeris of Wade et al. (Fig. 2), they fall on top of one another. Thus the light curves have the same shape for both eras. When one considers of the effects of slight differences in the period, the quoted error in the magnetic period is reduced by a factor of 4.
|Figure 2: Photometry of HD 115708 plotted according to the ephemeris of Wade et al. (1996) JD (positive magnetic maximum) = 2435997.50 + 5.07622 E with FCAPT values being given as closed squares and those of Wolff (1975) as plus signs|
This work was supported in part by NSF grants AST-9115114 and 9528506 and in part by grants from The Citadel Development Foundation. I appreciate the continuing efforts of L.J. Boyd, R.J. Dukes Jr., and G.P. McCook to keep the FCAPT operating properly and the useful comments of the referee G.A. Wade.
Copyright The European Southern Observatory (ESO)