X-ray Photoevaporation-starved T Tauri Accretion

TL;DR

This paper investigates how stellar X-ray emissions influence accretion processes in T Tauri stars, proposing that X-ray heating modulates accretion rates and explains observed correlations, challenging previous assumptions.

Contribution

It introduces a model where X-ray driven disk photoevaporation impacts accretion, providing a new explanation for the correlation between X-ray luminosity and accretion rates.

Findings

Accreting T Tauri stars are systematically fainter in X-rays.

A correlation exists between mass accretion rate and X-ray luminosity.

X-ray heating can drive disk photoevaporation at rates comparable to accretion.

Abstract

X-ray luminosities of accreting T Tauri stars are observed to be systematically lower than those of non-accretors. There is as yet no widely accepted physical explanation for this effect, though it has been suggested that accretion somehow suppresses, disrupts or obscures coronal X-ray activity. Here, we suggest that the opposite might be the case: coronal X-rays modulate the accretion flow. We re-examine the X-ray luminosities of T Tauri stars in the Orion Nebula Cluster and find that not only are accreting stars systematically fainter, but that there is a correlation between mass accretion rate and stellar X-ray luminosity. We use the X-ray heated accretion disk models of Ercolano et al. to show that protoplanetary disk photoevaporative mass loss rates are strongly dependent on stellar X-ray luminosity and sufficiently high to be competitive with accretion rates. X-ray disk heating appears to offer a viable mechanism for modulating the gas accretion flow and could be at least partially responsible for the observed correlation between accretion rates and X-ray luminosities of T Tauri stars.