X-ray Photoevaporation-Starved T Tauri Accretion
Abstract
X-ray luminosities of accreting T Tauri stars are observed to be systematically lower than those of nonaccretors. 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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2009
- DOI:
- 10.1088/0004-637X/699/1/L35
- arXiv:
- arXiv:0905.1690
- Bibcode:
- 2009ApJ...699L..35D
- Keywords:
-
- planetary systems: protoplanetary disks;
- stars: coronae;
- stars: formation;
- stars: pre-main sequence;
- stars: winds;
- outflows;
- X-rays: stars;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Galaxy Astrophysics;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 4 pages 3 figures, ApJ Letters, in press