MBCAA Observatory

V1309 Ori: an eclipsing polar

Observed: 26 Dec 2006, 15 Feb, 7 Nov 2007

Michel Bonnardeau
27 Dec 2007

Abstract

A phase plot of this eclipsing polar is presented. I try to model it with BinaryMaker3.

Introduction

V1309 Ori is a cataclysmic star, that is a binary with an accreting white dwarf. The white dwarf is strongly magnetized (about 10^8 gauss), its spin is synchronized with the orbital motion, and the accretion is funneled by the magnetic field (no accretion disk). This type of cataclysmic is a polar or an AM Her. It has an unusually long orbital/spin period of 8 h (Staude et al (2001)).

Observations

The observations were carried out with a 203mm SC telescope, a Clear filter, and a SBIG ST7E camera (KAF401E CCD). 171 images were obtained. Each exposure is 200s long, except for the first ones of each session which are 60s long.

For the differential photometry, the comparaison star is GSC100-01230 with an assumed unfiltered magnitude of 14.000. The check star is GSC100-01248 with an observed average magnitude of 14.334, an average statistical uncertainty of 0.022 mag and a standard deviation of 0.023.

The resulting light curves:

Red: V1309 Ori, blue: the check star shifted by +1.5mag. The error bars are +/- the 1 sigma statistical uncertainties.

The K star is shifted by +2.5 mag.

Phase plot

With the ephemeris of Staude et al (2001) t(E)=T+P*E with
P = 2,450,339.4363(6) (12 Sep 1996)
P = 0.332,611,94(8)
one has the phase plot:

The period being almost exactly 8h, the observations have to span almost one year to obtain a complete phase coverage:

BinaryMaker3 modeling

I fit the phase plot with the BinaryMaker3 software package. For the mass ratio and the inclination, I use the values of Staude et al (2001). I adjust the other parameters by hand. I need a hot spot (presumably where the accreted column collides with the white dwarf) at colatitude 118° and at longitude 273°. A fit is:

Red crosses: the observations, blue circle: the model.

All the BinaryMaker3 parameters are HERE.