  The software MAVKA is described, which was elaborated for statistically
optimal determination of the characteristics of the extrema of 1000+ variable
stars of different types, mainly eclipsing and pulsating. The approximations
are phenomenological, but not physical. As often, the discovery of a new
variable star is made on time series of a single-filter (single-channel) data,
and there is no possibility to determine parameters needed for physical
modelling (e.g. temperature, radial velocities, mass ratio of binaries).
Besides classical polynomial approximation "AP" (we limited the degree of the
polynomial from 2 to 9), there are realized symmetrical approximations
(symmetrical polynomials "SP", "wall-supported" horizontal line "WSL" and
parabola "WSP", restricted polynomials of non-integer order based on
approximations of the functions proposed by Andronov (2012) and Mikulasek
(2015) and generally asymmetric functions (asymptotic parabola "AP", parabolic
spline "PS", generalized hyperbolic secant function "SECH" and
"log-normal-like" "BSK"). This software is a successor of the "Observation
Obscurer" with some features for the variable star research, including a block
for "running parabola" "RP" scalegram and approximation. Whereas the RP is
oriented on approximation of the complete data set. MAVKA is pointed to parts
of the light curve close to extrema (including total eclipses and transits of
stars and exoplanets). The functions for wider intervals, covering the eclipse
totally, were discussed in 2017Ap.....60...57A . Global and local
approximations are reviewed in 2020kdbd.book..191A . The software is available
at http://uavso.org.ua/mavka and https://katerynaandrych.wixsite.com/mavka. We
have analyzed the data from own observations, as well as from monitoring
obtained at ground-based and space (currently, mainly, TESS) observatories. It
may be used for signals of any nature.
