3,126 research outputs found
Stark Broadening and White Dwarfs
White dwarf and pre-white dwarf atmospheres are one of the best examples for
the application of Stark broadening research results in astrophysics, due to
plasma conditions very favorable for this line broadening mechanism. For
example in hot hydrogen-deficient (pre-) white dwarf stars Teff = 75 000 K -
180 000 K and log g = 5.5-8 [cgs]. Even for much cooler DA and DB white dwarfs
with typical effective temperatures of 10 000 K - 20 000 K, Stark broadening is
usually the dominant broadening mechanism. In this review, Stark broadening in
white dwarf spectra is considered and the attention is drawn to the STARK-B
database (http://stark-b.obspm.fr/), containing Stark broadening parameters
needed for white dwarf spectra analysis and synthesis, as well as to the new
search facilities which will provide the collective effort to develop Virtual
Atomic and Molecular Data Center (VAMDC - http://vamdc.org/)
Global cross sections for Anosov flows
We provide a new criterion for the existence of a global cross section to a
volume-preserving Anosov flow. The criterion is expressed in terms of expansion
and contraction rates of the flow and is more general than the previous results
of similar kind.Comment: 14 pages, 1 figur
Landen inequalities for zero-balanced hypergeometric functions
For zero-balanced Gaussian hypergeometric functions
we determine maximal regions of plane where well-known Landen identities
for the complete elliptic integral of the first kind turn on respective
inequalities valid for each . Thereby an exhausting answer is given
to an open problem.Comment: 9 page
Broad spectral line and continuum variabilities in QSO spectra induced by microlensing of diffusive massive substructure
We investigate the variability of the continuum and broad lines in QSO
spectra (particularly in the H line and continuum at 5100 \AA
) caused by microlensing of a diffuse massive structure (like an open star
cluster). We modeled the continuum and line emitting region and simulate a
lensing event by a star cluster located in an intervening galaxy. Such a type
of microlensing event can have a significant influence on magnification and
centroid shift of the broad lines and continuum source. We explore
relationships between the continuum and broad line flux variability during the
microlensing event.Comment: 19 pages, 11 figure
- …