4 research outputs found
Discovery of the 1.80 hr Spin Period of the White Dwarf of the Symbiotic System BF Cyg
We report on the discovery of a coherent periodicity in the B light curve of
the symbiotic star BF Cyg. The signal was detected in some sections of the
light curve of the star recorded in the year 2003 as double hump periodic
variations with an amplitude of ~7 mmag.
In the year 2004 the signal was also present in only a subsection of the
light curve. In that year, the system was about twice as bright and the
amplitude of the oscillations was about half of what it was in 2003. In 2004
the cycle structure was of a single hump, the phase of which coincided with the
phase of one of the humps in the 2003 cycle. No periodic signal was detected in
a third, short series of observations performed in the year 2007, when the star
was three magnitudes brighter than in 2003.
We interpret the periodicity as the spin period of the white dwarf component
of this interacting binary system. We suggest that the signal in 2003
originated in two hot spots on or near the surface of the white dwarf, most
likely around the two antipodes of an oblique dipole magnetic field of this
star. Magnetic field lines funneled accreted matter from the wind of the cool
component to the pole areas, where the falling material created the hot spots.
This process is apparently intermittent in its nature. In 2004, the activity
near only one pole was enhanced enough to raise the signal above the threshold
of our detection ability.Comment: 7 pages, 5 figures, accepted for publication in MNRA
Metallicities of the beta Cephei stars from low-resolution ultraviolet spectra
We derive basic stellar parameters (angular diameters, effective
temperatures, metallicities) and interstellar reddening for all beta Cephei
stars observed during the IUE satellite mission, including those belonging to
three open clusters. The parameters are derived by means of an algorithmic
procedure of fitting theoretical flux distributions to the low-resolution IUE
spectra and ground-based spectrophotometric observations. Since the metallicity
has a special importance for pulsating B type stars, we focus our attention in
particular on this parameter.Comment: 15 pages, 8 figures, 5 table
La jurisdicción supranacional y la pena de muerte
No presenta resume