Photometry of the SW Sex-type nova-like BH Lyncis in high state

Aims: We present a photometric study of the deeply eclipsing SW Sex-type nova-like cataclysmic variable star BH Lyn Methods: Time-resolved V-band CCD photometry was obtained for seven nights between 1999 and 2004. Results: We determined 11 new eclipse timings of BH Lyn and derived a refined orbital ephemeris with an orbital period of 0.155875577(14) day. During the observations, BH Lyn was in high-state with V~15.5 mag. The star presents ~1.5 mag deep eclipses with mean full-width at half-flux of 0.0683(+/-0.0054)P_orb. The eclipse shape is highly variable, even changing form cycle to cycle. This is most likely due to accretion disc surface brightness distribution variations, most probably caused by strong flickering. Time-dependent accretion disc self-occultation or variations of the hot spot(s) intensity are also possible explanations. Negative superhumps with period of ~0.145 day are detected in two long runs in 2000. A possible connection between SW Sex and negative superhump phenomena through the presence of tilted accretion disc is discussed, and a way to observationally test this is suggested

Photometric study of selected cataclysmic variables II. Time-series photometry of nine systems

We present time-series photometry of nine cataclysmic variables: EI UMa, V844Her, V751 Cyg, V516 Cyg, GZ Cnc, TY Psc, V1315 Aql, ASAS J002511+1217.12, V1315 Aql and LN UMa. The observations were conducted at various observatories, covering 170 hours and comprising 7,850 data points in total. For the majority of targets we confirm previously reported periodicities and for some of them we give, for the first time, their spectroscopic orbital periods. For those dwarf-nova systems which we observed during both quiescence and outburst, the increase in brightness was followed by a decrease in the amount of flickering. Quasi-periodic oscillations have either been discovered, or were confirmed. For the eclipsing system V1315 Aql we have covered 9 eclipses, and obtained a refined orbital ephemeris. We find that, during its long baseline of observations, no change in the orbital period of this system has occurred. V1315 Aql also shows eclipses of variable depth.Comment: 30 pages, 16 figures, 4 tables. Submitted to JA

Correcting second-order contamination in low-resolution spectra

An empirical method for correcting low-resolution astronomical spectra for second-order contamination is presented. The method was developed for correcting spectra obtained with grism #4 of the ALFOSC spectrograph at the Nordic Optical Telescope and the performance is demonstrated on spectra of two nearby bright Type Ia supernovae.Comment: accepted for publication in Astronomical Notes (Astronomische Nachrichten

H-alpha variability of the recurrent nova T Coronae Borealis

We analyze H-alpha observations of the recurrent nova T CrB obtained during the last decade. For the first time the H-alpha emission profile is analyzed after subtraction of the red giant contribution. Based on our new radial velocity measurements of the H-alpha emission line we estimate the component masses of T CrB. It is found that the hot component is most likely a massive white dwarf. We estimate the inclination and the component masses to be i~67 deg, Mwd = 1.37 +/-0.13 Msun and Msec=1.12 +/-0.23 Msun, respectively. The radial velocity of the central dip in the H-alpha profile changes nearly in phase with that of the red giant's absorption lines. This suggests that the dip is most likely produced by absorption in the giant's wind. Our observations cover an interval when the H-alpha and the U-band flux vary by a factor of ~6, while the variability in B and V is much smaller. Based on our observations, and archival ultraviolet and optical data we show that the optical, ultraviolet and H-alpha fluxes strongly correlate. We argue that the presence of an accretion disc can account for most of the observed properties of T CrB.Comment: 8 pages, 6 EPS figures, to appear in A&