Nova V5116 Sgr and searching for superhumps in nova remnants

Abstract

We present the period analysis of unfiltered photometric observations of V5116 Sgr (Nova Sgr 2005 #2) and we search for superhump candidates in novae remnants. The PDM method for period analysis is used. The masses of the novae componets are estimated from the secondary mass -- orbital period and primary mass -- decline time relations. We found that 13 nights of V5116 Sgr observations in the year 2006 are modulated with a period of $0.1238 \pm 0.0001$ d ($2.9712 \pm 0.0024$ h). Following the shape of the phased light curves and no apparent change in the value of the periodicity in different subsamples of the data, we interpret the period as orbital in nature. The binary system then falls within the period gap of the orbital period distribution of cataclysmic variables. From the maximum magnitude -- rate of decline relation, we estimate the maximum absolute visual magnitude of $M_{\rm Vmax} = -8.85 \pm 0.04$ mag using the measured value of decline $t_{\rm 2} = 6.5 \pm 1.0$ d. The mass-period relation for cataclysmic variables yields a secondary mass estimate of about $0.26 \pm 0.05 {\rm M}_{\rm \odot}$. We propose that V5116 Sgr is a high inclination system showing an irradiation effect of the secondary star. No fully developed accretion disc up to the tidal radius with the value lower than $3.5 10^{10}$ cm is probable. The mass ratio was estimated in a few novae and the presence or absence of superhumps in these systems was compared with the mass ratio limit for superhumps of about 0.35. We found that in the majority of novae with expected superhumps, this variability has not been found yet. Therefore, more observations of these systems is encouraged.