Title: DZ Cha: a bona fide photoevaporating disc,
Abstract: DZ Cha is a weak-lined T Tauri star (WTTS) surrounded by a bright
protoplanetary disc with evidence of inner disc clearing. Its narrow $\Ha$ line
and infrared spectral energy distribution suggest that DZ Cha may be a
photoevaporating disc. We aim to analyse the DZ Cha star + disc system to
identify the mechanism driving the evolution of this object. We have analysed
three epochs of high resolution optical spectroscopy, photometry from the UV up
to the sub-mm regime, infrared spectroscopy, and J-band imaging polarimetry
observations of DZ Cha. Combining our analysis with previous studies we find no
signatures of accretion in the $\Ha$ line profile in nine epochs covering a
time baseline of $\sim20$ years. The optical spectra are dominated by
chromospheric emission lines, but they also show emission from the forbidden
lines [SII] 4068 and [OI] 6300$\,\AA$ that indicate a disc outflow. The
polarized images reveal a dust depleted cavity of $\sim7$ au in radius and two
spiral-like features, and we derive a disc dust mass limit of
$M_\mathrm{dust}<3\MEarth$ from the sub-mm photometry. No stellar ($M_\star >
80 \MJup$) companions are detected down to $0\farcs07$ ($\sim 8$ au,
projected). The negligible accretion rate, small cavity, and forbidden line
emission strongly suggests that DZ Cha is currently at the initial stages of
disc clearing by photoevaporation. At this point the inner disc has drained and
the inner wall of the truncated outer disc is directly exposed to the stellar
radiation. We argue that other mechanisms like planet formation or binarity
cannot explain the observed properties of DZ Cha. The scarcity of objects like
this one is in line with the dispersal timescale ($\lesssim 10^5$ yr) predicted
by this theory. DZ Cha is therefore an ideal target to study the initial stages
of photoevaporation.