69,751 research outputs found
Spatial distribution and galactic model parameters of cataclysmic variables
The spatial distribution, galactic model parameters and luminosity function
of cataclysmic variables (CVs) in the solar neighbourhood have been determined
from a carefully established sample of 459 CVs. The sample contains all of the
CVs with distances computed from the Period-Luminosity-Colours (PLCs) relation
of CVs which has been recently derived and calibrated with {\em 2MASS}
photometric data. It has been found that an exponential function fits best to
the observational z-distributions of all of the CVs in the sample, non-magnetic
CVs and dwarf novae, while the sech^{2} function is more appropriate for
nova-like stars and polars. The vertical scaleheight of CVs is 15814 pc
for the {\em 2MASS} J-band limiting apparent magnitude of 15.8. On the other
hand, the vertical scaleheights are 12820 and 1605 pc for dwarf novae
and nova-like stars, respectively. The local space density of CVs is found to
be pc^{-3} which is in agreement with the lower limit of
the theoretical predictions. The luminosity function of CVs shows an increasing
trend toward higher space densities at low luminosities, implying that the
number of short-period systems should be high. The discrepancies between the
theoretical and observational population studies of CVs will almost disappear
if for the z-dependence of the space density the sech^{2} density function is
used.Comment: 29 pages, 9 figures and 5 tables, accepted for publication in New
Astronom
On the eclipsing cataclysmic variable star HBHA 4705-03
We present observations and analysis of a new eclipsing binary HBHA 4705-03.
Using decomposition of the light curve into accretion disk and hot spot
components, we estimated photometrically the mass ratio of the studied system
to be q=0.62 +-0.07. Other fundamental parameters was found with modeling. This
approach gave: white dwarf mass M_1 = (0.8 +- 0.2) M_sun, secondary mass
M_2=(0.497 +- 0.05) M_sun, orbital radius a=1.418 R_sun, orbital inclination i
= (81.58 +- 0.5) deg, accretion disk radius r_d/a = 0.366 +- 0.002, and
accretion rate dot{M} = (2.5 +- 2) * 10^{18}[g/s], (3*10^{-8} [M_sun/yr]).
Power spectrum analysis revealed ambiguous low-period Quasi Periodic
Oscillations centered at the frequencies f_{1}=0.00076 Hz, f_2=0.00048 Hz and
f_3=0.00036 Hz. The B-V=0.04 [mag] color corresponds to a dwarf novae during an
outburst. The examined light curves suggest that HBHA 4705-03 is a nova-like
variable star.Comment: 7 figures and 2 tables, accepted for publication in Acta Astronomic
Metallicity Calibration and Photometric Parallax Estimation: I. UBV photometry
We present metallicity and photometric parallax calibrations for the F and G
type dwarfs with photometric, astrometric and spectroscopic data. The sample
consists of 168 dwarf stars covering the colour, iron abundance and absolute
magnitude intervals mag, dex and
mag, respectively. The means and standard deviations of the
metallicity and absolute magnitude residuals are small, i.e.
and dex, and and mag, respectively, which indicate
accurate metallicity and photometric parallax estimations.Comment: 13 pages, 11 figures and 2 tables, accepted for publication in
Astrophysics and Space Scienc
Matching novel face and voice identity using static and dynamic facial images
Research investigating whether faces and voices share common source identity information has offered contradictory results. Accurate face-voice matching is consistently above chance when the facial stimuli are dynamic, but not when the facial stimuli are static. We tested whether procedural differences might help to account for the previous inconsistencies. In Experiment 1, participants completed a sequential two-alternative forced choice matching task. They either heard a voice and then saw two faces or saw a face and then heard two voices. Face – voice matching was above chance when the facial stimuli were dynamic and articulating, but not when they were static. In Experiment 2, we tested whether matching was more accurate when faces and voices were presented simultaneously. The participants saw two face–voice combinations, presented one after the other. They had to decide which combination was the same identity. As in Experiment 1, only dynamic face–voice matching was above chance. In Experiment 3, participants heard a voice and then saw two static faces presented simultaneously. With this procedure, static face–voice matching was above chance. The overall results, analyzed using multilevel modeling, showed that voices and dynamic articulating faces, as well as voices and static faces, share concordant source identity information. It seems, therefore, that above-chance static face–voice matching is sensitive to the experimental procedure employed. In addition, the inconsistencies in previous research might depend on the specific stimulus sets used; our multilevel modeling analyses show that some people look and sound more similar than others
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