Indications from Gaia data release 2 (DR2) are that the tip of the red giant
branch (TRGB, a population II standard candle related to the helium flash in
low mass stars) is close to -4 in absolute I magnitude in the Cousins
photometric system. Our sample is high latitude southern stars from the thick
disk and inner halo, and our result is consistent with longstanding findings
from globular clusters, whose distances were calibrated with RR Lyrae stars. As
the Gaia mission proceeds, there is every reason to think an accurate Galactic
geometric calibration of TRGB will be a significant outcome.Comment: to appear in PAS
