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We show that if young low mass stars undergo vigorous X-ray driven discwinds, these may be detected in clusters through their interaction withionising radiation from massive stars. We argue that in the ONC (Orion NebulaCluster) one should see $\sim$ 10s of `X-ray proplyds' ( objects with opticallyimaged offset ionisation fronts) in the range $0.3-0.6$pc from $\theta_1$C Ori(the dominant O star in the ONC). Such objects lie outside the central `FUVzone' in the ONC where proplyds are instead well explained by neutral windsdriven by external Far Ultraviolet (FUV) emission from $\theta_1$C. We showthat the predicted numbers and sizes of X-ray proplyds are compatible withthose observed and that this may also explain at least some of the far flungproplyds seen in the Carina nebula. We compare the sizes of observed proplydsoutside the FUV region of the ONC with model predictions based on the currentobserved X-ray luminosities of these sources ( bearing in mind that the currentsize is actually set by the X-ray luminosity a few hundred years ago, $\sim$the flow time to the ionisation front). We discuss whether variability on thistimescale can plausibly explain proplyd size data on a case by case basis. Wealso show that the predicted radio free-free emission signature of X-rayproplyds is readily detectable. Monitoring is however required to distinguishsuch emission from non-thermal emission from active coronae. We also predictthat it is only at $> 1$ pc from $\theta_1$C that the free-free emission fromsuch offset ionised structures would be clearly distinguishable from anexternally driven ionised disc wind. We argue that the fortuitous proximity ofmassive stars in the ONC can be used as a beacon to light up internally drivenX-ray winds and that this is a promising avenue for observationally testingX-ray photoevaporation.

Probing X-ray photoevaporative winds through their interaction with ionising radiation in cluster environments: the case for X-ray proplyds