A spatially dependent correction of Gaia EDR3 parallax zero-point offset
  based on 0.3 million LAMOST DR8 giant stars
  We have studied the zero-point offset of Gaia early Data Release 3 (EDR3)
parallaxes based on a sample of 0.3 million giant stars built from the LAMOST
data with distance accuracy better than 8.5\%. The official parallax zero-point
corrections largely reduce the global offset in the Gaia EDR3 parallaxes: the
global parallax offsets are $-$27.9 $\mu$as and $-$26.5 $\mu$as (before
correction) and $+$2.6 $\mu$as and $+$2.9 $\mu$as (after correction) for the
five- and six-parameter solutions, respectively. The bias of the raw parallax
measurements is significantly dependent on the $G$ magnitudes, spectral colors,
and positions of stars. The official parallax zero-point corrections could
reduce parallax bias patterns with $G$ magnitudes, while could not fully
account the patterns in the spaces of the spectral colors and positions. In the
current paper, a spatially dependent parallax zero-point correction model for
Gaia EDR3 five-parameter solution in the LAMOST footprint is firstly provided
with the advantage of huge number of stars in our sample.
