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

Abstract

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 An analysis of our data, along with all previously available timings (36 published and 16 unpublished), yields a best-fitting linear ephemeris of BJDecl = 2,453,403.7611(2) + 0.269,374,43(2)E. We find a somewhat improved fit with a quadratic ephemeris given by: BJDecl = 2,453,403.7598 + 0.269,374,87 E − 2.0 × 10−11 E 2, which suggests that the orbital period may be decreasing at a rate given by P ˙ ≃ − 1.5 × 10 − 10 .