  We propose that a non-thermal X-ray arc inside the remnant of Tycho's
supernova (SN) represents the interaction between the SN ejecta and the
companion star's envelope lost in the impact of the explosion. The X-ray
emission of the remnant further shows an apparent shadow casted by the arc in
the opposite direction of the explosion site, consistent with the blocking of
the SN ejecta by the envelope. This scenario supports the single degenerate
binary origin of Tycho's SN. The properties of the X-ray arc, together with the
previous detection of the companion candidate and its space velocity by
Ruiz-Lapuente et al. (2004) and Hern\'{a}ndez et al.(2009), enables us to
further infer 1) the progenitor binary has a period of 4.9$^{+5.3}_{-3.0}$
days, 2) the companion gained a kick velocity of 42$\pm$30 km s$^{-1}$, and 3)
the stripped envelope mass is about 0.0016($\leq0.0083$) $M_{\sun}$. However,
we notice that the nature of the companion candidate is still under debate, and
the above parameters need to be revised according to the actual properties of
the companion candidate. Further work to measure the proper motion of the arc
and to check the capability of the interaction to emit the amount of X-rays
observed from the arc is also needed to validate the current scenario.
