Linearly Polarized Millimeter and Submillimeter Continuum Emission of
  Sgr A* Constrained by ALMA
  Our aim is to characterize the polarized continuum emission properties
including intensity, polarization position angle, and polarization percentage
of Sgr A* at $\sim$100 (3.0 mm), $\sim$230 (1.3 mm), $\sim$345 (0.87 mm),
$\sim$500 (0.6 mm), and $\sim$700 GHz (0.43 mm). We report continuum emission
properties of Sgr A* at the above frequency bands, based on the Atacama Large
Millimeter Array (ALMA) observations. We measured flux densities of Sgr A* from
ALMA single pointing and mosaic observations. We performed sinusoidal fittings
to the observed (XX-YY)/I intensity ratios, to derive the polarization position
angles and polarization percentages. We successfully detect polarized continuum
emission from all observed frequency bands. We observed lower Stokes I
intensity at $\sim$700 GHz than that at $\sim$500 GHz, which suggests that
emission at $\gtrsim$500 GHz is from optically thin part of a synchrotron
emission spectrum. Both the Stokes I intensity and the polarization position
angle at our highest observing frequency of $\sim$700 GHz, may be varying with
time. However, we do not yet detect variation in the polarization percentage at
$>$500 GHz. The polarization percentage at $\sim$700 GHz is likely lower than
that at $\sim$500 GHz. By comparing the $\sim$500 GHz and $\sim$700 GHz
observations with the observations at lower frequency bands, we suggest that
the intrinsic polarization position angle of Sgr A* is varying with time. This
paper also reports the measurable polarization properties from the observed
calibration quasars. The future simultaneous multi-frequency polarization
observations are required for clarifying the time and frequency variation of
polarization position angle and polarization percentage.
