arXiv subjects

P. Rodriguez-Gil

Publications and source records attributed to P. Rodriguez-Gil.

58 records · Page 4Linked to original sources

arXiv2001

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).

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arXiv2001

Photometric Variability of the Gravitational Lens 0142-100 (UM 673)

We present the results of a photometric CCD monitoring of the gravitational lens system UM 673, that took place from 1995 to 2000. In total, the doubly-imaged quasar was observed in the R-band during 29 photometric nights, using optical telescopes with dimensions in the range 0.6 m to 1.3 m. We detected a significant variability in the total light of the UM 673 system, that is, in the light of the two QSO images plus the lensing galaxy. With respect to the magnitude of the gravitational lens system at its discovery, in 1986, UM 673 was 0.3 magnitude brighter. Furthermore, our December 1996 measurements show that between November 1995 and October 1997 the system became even brighter, reaching a magnitude difference of 0.5 magnitude with respect to its discovery value. We also present R magnitudes and V-R colours of seven field stars situated in the vicinity of the lens, based on a 3.5-month monitoring during the year 2000.

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arXiv2000

Evidence of magnetic accretion in an SW Sex star: discovery of variable circular polarization in LS Pegasi

We report on the discovery of variable circular polarization in the SW Sex star LS Pegasi. The observed modulation has an amplitude of ~0.3 % and a period of 29.6 minutes, which we assume as the spin period of the magnetic white dwarf. We also detected periodic flaring in the blue wing of Hbeta, with a period of 33.5 minutes. The difference between both frequencies is just the orbital frequency, so we relate the 33.5-min modulation to the beat between the orbital and spin period. We propose a new accretion scenario in SW Sex stars, based on the shock of the disk-overflown gas stream against the white dwarf's magnetosphere, which extends to the corotation radius. From this geometry, we estimate a magnetic field strength of B(1) ~ 5-15 MG. Our results indicate that magnetic accretion plays an important role in SW Sex stars and we suggest that these systems are probably Intermediate Polars with the highest mass accretion rates.

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arXiv1999

Long-term photometry of WX Arietis: evidence for eclipses and dips

We present R-band photometry of the SW Sex-type cataclysmic variable WX Arietis made in October 1995 and August 1998-February 1999. Contrary to previous results, we find that WX Ari is an eclipsing system with an orbital inclination of ~72 deg. The R-band light curves display highly variable, shallow eclipses ~0.15-mag deep and ~40 min long. The observed eclipse depth suggests a partial eclipse of the accretion disc. The light curves also show a wide dip in brightness centred at orbital phase ~0.75 and a hump close to the opposite phase at ~0.2. The observed dip may be explained by the probable vertical thickening of the outer rim of the accretion disc downstream from the bright spot. We also demonstrate that the disc brightness in all SW Sex systems is nearly the same. This implies that the orbital inclination of these systems is only a function of eclipse depth.

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