NSV 13983: A New Dwarf Nova in the Period Gap

Aims. NSV 13983 is catalogued as a dwarf nova based on a reported outburst from 2005. The system has not yet been studied spectroscopically. We attempt to confirm its nature as a dwarf nova and determine its orbital period. Methods. We derive the orbital period by using time-resolved spectroscopic data to measure radial velocities. Results. The average spectrum shows evidence that the system is a dwarf nova in quiescence. The radial velocity curves derived from measurements of the spectral lines H\alpha and H\beta, show a clear modulation with a period of 2.76 h. This places NSV 13983 below the upper edge of the gap in the period distribution of cataclysmic variables, implying that it is the 14th dwarf nova in the gap.Comment: 3 pages, 4 figures, 1 tables, accepted by A&

Transits and starspots in the WASP-19 planetary system

We have developed a new model for analysing light curves of planetary transits when there are starspots on the stellar disc. Because the parameter space contains a profusion of local minima we developed a new optimisation algorithm which combines the global minimisation power of a genetic algorithm and the Bayesian statistical analysis of the Markov chain. With these tools we modelled three transit light curves of WASP-19. Two light curves were obtained on consecutive nights and contain anomalies which we confirm as being due to the same spot. Using these data we measure the star's rotation period and velocity to be $11.76 \pm 0.09$ d and $3.88 \pm 0.15$\kms, respectively, at a latitude of 65$^\circ$. We find that the sky-projected angle between the stellar spin axis and the planetary orbital axis is $\lambda = 1.0^{\circ} \pm 1.2^{\circ}$, indicating axial alignment. Our results are consistent with and more precise than published spectroscopic measurements of the Rossiter-McLaughlin effect.Comment: 9 pages, 6 figures, 5 table

Search for brown-dwarf like secondaries in cataclysmic variables II

We have examined VTL/ISAAC 1-2.5 \umum spectroscopy of a sample of short orbital period cataclysmic variables which are candidates for harboring substellar companions. We provide descriptions of the infrared spectrum of \hbox{EI Psc}, \hbox{V834 Cen}, \hbox{WX Cet}, \hbox{VW Hyi}, \hbox{TY PsA} and \hbox{BW Scl}. Fitting of the IR spectral energy distribution (SED) was performed by comparing the observed spectrum with late-type templates. Absorption features of the secondary star were detected in \hbox{EI Psc} and \hbox{V834 Cen}, consistent with dwarf secondaries of spectral type K 5 $\pm$ 1 and M 8 $\pm$ 0.5, respectively. In addition, we report the first detection of the secondary star in \hbox{VW Hyi}. The SED in this case is well matched by an L 0 $\pm$ 2 type secondary contributing 23 per cent to the overall flux at $\lambda$ = 1.15 \umum. This is a surprising result for a system with a relatively high mass transfer rate. We discuss the implication of our findings on the current scenarios for cataclysmic variable star evolution.Comment: accepted for publication in MNRA