  MEGARA is the optical integral field and multi-object spectrograph at the
Gran Telescopio Canarias. We have created MEGASTAR, an empirical library of
stellar spectra obtained using MEGARA at high resolution $R=20\,000$ (FWHM),
available in two wavelength ranges: one centered in H${\alpha}$, from 6420 to
6790\,\AA\ and the other centered in the \ion{Ca}{ii} triplet, from 8370 to
8885\,\AA\ (\mbox{HR-R} and \mbox{HR-I} VPH-grating configurations). In this
work, we use MEGASTAR spectra, combination of these two short wavelength
intervals, to estimate the stellar parameters namely effective temperature,
surface gravity and metallicity (and their associated errors) for a sample of
351 MEGASTAR members with spectral types earlier than B2. We have applied a
$\chi^2$ technique by comparing MEGASTAR data to theoretical stellar models.
For those stars with stellar parameters derived in the literature, we have
obtained a good agreement between those published parameters and ours. Besides
the stellar parameters, we also provide several products like the rectified
spectra, radial velocities and stellar indices for this sample of stars. In a
near future, we will use MEGASTAR spectra and their derived stellar parameters
to compute stellar population evolutionary synthesis models, which will
contribute to a better interpretation of star clusters and galaxies spectra
obtained with MEGARA.
