  In Kato (2015, arXiv:1507.07659), I suggested that the magnitude when
ordinary superhumps appear can be a standard candle for WZ Sge stars. Using
Gaia EDR3 parallaxes, I studied 53 WZ Sge stars to examine this suggestion. The
analysis indicated that the absolute magnitudes when ordinary superhumps appear
are strongly dependent on orbital inclinations, which is consistent with what
is expected for the projected area for optical thick accretion disks. I showed
that there is a linear relation between these absolute magnitudes and
logarithmic amplitudes of early superhumps, which are also dependent on the
inclinations. I confirmed that the magnitude when ordinary superhumps appear
can be used as the standard candle for WZ Sge stars particularly when the
amplitude of early superhumps is observationally known. The resultant median
absolute magnitude when ordinary superhumps appear was $+$5.4 (for an average
inclination of 1 radian). A few objects with multiple rebrightenings, which are
good candidates for period bouncers, showed slightly fainter absolute
magnitudes, although the majority of the same class of objects follows the
relation. Using the relation, I derived an empirical relation between the
inclination and the amplitude of early superhumps. I applied the relation to
MASTER OT J030227.28$+$191754.5, which was initially considered as a possible
optical counterpart of the high-energy neutrino event IceCube-211125A, and
concluded that this WZ Sge star was one of the faintest before the outburst and
one of the brightest around the optical peak in terms of absolute magnitudes.

Solar and Stellar Astrophysics