Updated Ephemeris and Evidence for a Period Change in the Eclipsing Novalike Variable 1RXS J064434.5+334451

Abstract

We report seven new eclipse timings for the novalike variable 1RXS J064434.5+334451. An analysis of our data, along with all previously available timings (36 published and 16 unpublished), yields a best-fitting linear ephemeris of BJD$_\mathrm{ecl} = 2,453,403.7611(2) + 0.269~374~43(2)~\mathrm{E}$. We find a somewhat improved fit with a quadratic ephemeris given by: BJD$_\mathrm{ecl} = 2,453,403.7598 + 0.269~374~87~\mathrm{E} - 2.0\times10^{-11}~\mathrm{E}^2$, which suggests that the orbital period may be decreasing at a rate given by $\dot P \simeq -1.5\times10^{-10}$.