V348 Puppis: a new SW Sex star in the period gap

We present time-resolved optical spectroscopy and photometry of the nova-like cataclysmic variable V348 Puppis. The system displays the same spectroscopic behaviour as SW Sex stars, so we classify V348 Pup as a new member of the class. V348 Pup is the second SW Sex system (the first is V795 Herculis) which lies in the period gap. The spectra exhibit enhanced HeII 4686 emission, reminiscent of magnetic cataclysmic variables. The study of this emission line gives a primary velocity semi-amplitude of K1 ~= 100 km/s. We have also derived the system parameters, obtaining: M1 ~= 0.65 Msun, M2 ~= 0.20 Msun (q ~= 0.31), i ~= 80 deg and K2 ~= 323 km/s. The spectroscopic behaviour of V348 Pup is very similar to that of V795 Her, with the exception that V348 Pup shows deep eclipses. We have computed the ``0.5-absorption'' spectrum of both systems, obtaining spectra which resemble the absorption spectrum of a B0 V star. We propose that absorption in SW Sex systems can be produced by a vertically extended atmosphere which forms where the gas stream re-impacts the system, either at the accretion disc or at the white dwarf's magnetosphere (assuming a magnetic scenario).Comment: 6 pages, 10 figures, accepted for publication in MNRA

Multiband echo tomography of Sco X-1

We present preliminary results of a simultaneous X-ray/optical campaign of the prototypical LMXB Sco X-1 at 1-10 Hz time resolution. Lightcurves of the high excitation Bowen/Hell emission lines and a red continuum at lambda(c) similar to 6000 angstrom were obtained through narrow interference filters with ULTRACAM, and these were cross-correlated with simultaneous RXTE X-ray lightcurves. We find evidence for correlated variability, in particular when Sco X-1 enters the Flaring branch. The Bowen/Hell lightcurves lag the X-ray lightcurves with a light travel time which is consistent with reprocessing in the companion star while the continuum lightcurves have shorter delays consistent with reprocessing in the accretion disc

Infrared light curves and spectroscopic classification of the Algol system UX Her

We present the first light curves in the infrared J, H, and K bands of UX Her and analyze them together with published light curves in B and V in order to determine the physical parameters of the system. Based on the spectra of UX Her and standard stars in the region 8440-8870 Å, we classify the primary component of the binary as a type A2-3 V star. From the absolute radii of the stars that we derive from the light-curve analysis, we find that none of the components of the binary are filling their Roche lobes. Considering the contributions of the secondary star to the total light given by the light-curve solutions, and the measured B, V, J, H, and K magnitudes at maxima and during the eclipses, we find good agreement with those predicted from stellar atmosphere models for effective temperatures of the stellar components: Teff.1≃9000 K and Teff.2∼4500 K, with the system at a distance d≃280 pc. © 1997 American Astronomical Society

Dynamical constraints on the neutron star mass in EXO 0748-676

We present Very Large Telescope (VLT) intermediate resolution spectroscopy of UY Vol, the optical counterpart of the low mass X-ray binary (LMXB) X-ray burster EXO 0748-676. By using Doppler tomography we detect narrow components within the broad He II lambda 4542, lambda 4686 and lambda 5412 emission lines. The phase, velocity and narrowness of these lines are consistent with their arising from the irradiated hemisphere of the donor star, as has been observed in a number of LMXBs. Under this assumption, we provide the first dynamical constraints on the stellar masses in this system. In particular, we measure K-2 > K-em = 300 +/- 10 km s(-1). Using this value, we derive 1 M-circle dot = 1.5 M-circle dot for the case of a main sequence companion star. Our results are consistent with the presence of a massive neutron star as has been suggested by Ozel (2006), although we cannot discard the canonical value of similar to 1.4 M-circle dot