First photometric study of ultrashort-period contact binary 1SWASP J140533.33+114639.1

In this paper, CCD photometric light curves for the short-period eclipsing binary 1SWASP J140533.33+114639.1 (hereafter J1405) in the $BVR$ bands are presented and analyzed using the 2013 version of the Wilson-Devinney (W-D) code. It is discovered that the J1405 is a W-subtype shallow contact binary with a contact degree of $f$ = 7.9$\pm$ 0.5\% and a mass ratio of $q$ = 1.55 $\pm$ 0.02. In order to explain the asymmetric light curves of the system, a cool star-spot on the more massive component was employed. This shallow contact eclipsing binary may be formed from a short-period detached system through the orbital shrinkage due to angular momentum loss. Based on $(O-C)$ method, the variation of the orbital period was studied using all the available times of the minimum light. The $(O-C)$ diagram reveals that the period is increasing continuously at a rate of $dP/dt=+2.09\times{10^{-7}}$days yr$^{-1}$, which can be explained by mass transfer from the less massive component to the more massive one.