X-ray echoes of infrared flaring in Sgr A*
  Sgr A* exhibits flaring in the infrared several times each day, occasionally
accompanied by flaring in X-rays. The infrared flares are believed to arise
through synchrotron emission from a transient population of accelerated
electrons. The X-ray flaring has been interpreted as self-synchrotron-compton,
inverse compton, or synchrotron emission associated with the transient
electrons. Here I consider the upscattering of infrared flare photons by
relativistic thermal electrons in the accretion flow around Sgr A*. Typical
profiles of electron density and temperature in the accretion flow are adopted
and the X-ray light curves produced by upscattering of infrared flare photons
by the accretion flow are computed. Peak X-ray luminosities between 1e33 and
1e34 erg/s are attained for a 10 mJy near-infrared flare, compatible with
observed coincident infrared/X-ray flares from Sgr A*. Even if this process is
not responsible for the observed flares it still presents a serious constraint
on accretion flow models, which must avoid over-producing X-rays and also
predicting observable time lags between flaring in infrared and in X-rays.
Future high-resolution infrared instrumentation will be able to place the
location of the infrared flare and in coordination with the X-ray would
severely constrain the disc geometry and the radial profiles of electron
density and temperature in the accretion flow.
