5 AD Phe

The eclipsing binary AD Phe (also CD  $-40^{\circ}$ 288, CPD  $-40^{\circ}$ 117, HIP 5955, PPM 276874, CSV 5906, S7148, BV 1260, FL 90; $\alpha_{2000} = 1^{\rm h}16^{\rm m}38.1^{\rm s}$, $\delta_{2000} =$ $-39^{\circ}42\hbox{$^\prime$ }31.3\hbox{$^{\prime\prime}$ }$, $V_{\max}=$ 10.29 mag) is a relatively seldom investigated southern system. It was discovered to be variable star photographically by Hoffmeister (1963). Strohmeier & Bauernfeind (1969) published times of minimum light and determined the first light elements:

$${\rm Pri.~Min.} = {\rm HJD~24~28672.685} + 0\hbox{$.\!\!^{\rm d}$ }5132295 \cdot E.$$

Several UBV photoelectric times of minimum were obtained by Cerruti (1986) at Cerro Tololo Inter-American Observatry in Chile in August 1981. (In the title of this paper, AD Phe was erroneously designated as AG Phe). He improved light elements and found a reliable shortening of the period:

$$\begin{eqnarray*}{\rm Pri.~Min.} &=& {\rm HJD~24~36781.4224}\\ && + 0\hbox{$.\!... ...}37992632 \cdot E - 0\hbox{$.\!\!^{\rm d}$ }643 \ 10^{-10} E ^2. \end{eqnarray*}$$

The precise $BVRI_{\rm C}$ photometry of AD Phe was obtained by McFarlane & Hilditch (1987) at SAAO in October 1982. They derived five times of minimum light and calculated the revised ephemeris:

$${\rm Pri.~Min.} = {\rm HJD~24~46003.3683} + 0\hbox{$.\!\!^{\rm d}$ }3799344 \cdot E .$$

They also obtained a photometric solution, which was insensitive to the mass ratio. To our knowledge this star has not been studied spectroscopically since its discovery. More than 15 years have elapsed since its last study, thus AD Phe was also included in our photometric program at SAAO. Apart from the eclipses included in Table 1 by Cerruti (1986) we have adopted, for a new O-C diagram analysis, the minima given in McFarlane & Hilditch (1987) and new timings resulting from the Hipparcos photometry. Using this data base, which includes 56 times of minima we improved the linear light elements after JD 2444800

${\rm Pri.~Min.} = {\rm HJD~24~45998.4292}+ 0\hbox{$.\!\!^{\rm d}$ }37992454 \cdot E,$

$\pm 0.0002$ $\pm 0.00000002$

which can serve also for the prediction of future times of minima. The corresponding O-C diagram is plotted in Fig. 6.

Figure 6: O-C diagram for AD Phe. The full line corresponds to our linear ephemeris, the dashed curve represents less probable parabolic light elements