  AIMS. We study the variability of the Fe 6.4 KeV emission line from the Class
I young stellar object Elias 29 in the Rho-Oph cloud. METHODS. We analysed the
data from Elias 29 collected by XMM during a nine-day, nearly continuous
observation of the Rho-Oph star-forming region (the Deep Rho-Oph X-ray
Observation, named Droxo). The data were subdivided into six homogeneous time
intervals, and the six resulting spectra were individually analysed. RESULTS.
We detect significant variability in the equivalent width of the Fe 6.4 keV
emission line from Elias 29. The 6.4 keV line is absent during the first time
interval of observation and appears at its maximum strength during the second
time interval (90 ks after Elias 29 undergoes a strong flare). The X-ray
thermal emission is unchanged between the two observation segments, while line
variability is present at a 99.9% confidence level. Given the significant line
variability in the absence of variations in the X-ray ionising continuum and
the weakness of the photoionising continuum from the star's thermal X-ray
emission, we suggest that the fluorescence may be induced by collisional
ionisation from an (unseen) population of non-thermal electrons. We speculate
on the possibility that the electrons are accelerated in a reconnection event
of a magnetically confined accretion loop, connecting the young star to its
circumstellar disk.
