Measurement of The Broad Line Region Size in a Luminous MACHO Quasar
  We measure the broad emission line region (BLR) size of a luminous, L~1E47
erg/s, high-z quasar using broadband photometric reverberation mapping. To this
end, we analyze ~7.5 years of photometric data for MACHO 13.6805.324 (z~1.72)
in the B and R MACHO bands and find a time delay of 180+/-40 days in the rest
frame of the object. Given the spectral-variability properties of high-z
quasars, we associate this lag with the rest-UV iron emission blends. Our
findings are consistent with a simple extrapolation of the BLR size-luminosity
relation in local active galactic nuclei to the more luminous, high-z quasar
population. Long-term spectroscopic monitoring of MACHO 13.6805.324 may be able
to directly measure the line-to-continuum time-delay and test our findings.
