Detection of a Cool, Accretion-Shock-Generated X-Ray Plasma in EX Lupi During the 2008 Optical Eruption

摘要: EX Lupi is the prototype for a class of young, pre-main-sequence stars which are observed to undergo irregular, presumably accretion-generated, optical outbursts that result in several magnitude rise flux. was optically erupt 2008 January, triggering Chandra ACIS Target Opportunity observations shortly thereafter. We find very strong evidence most X-ray emission first few months after outburst generated by accretion circumstellar material onto stellar photosphere. Specifically, we correlation between decreasing and fluxes following peak optical, suggests these declines both declining rate. In addition, our models spectrum, ~0.4 keV plasma component, as expected shocks on low-mass, stars. From March through October, this cool component appeared fade returned its quiescent level consistent with decrease overall measure accretion-shock-generated plasma. The small increase flux during similar what previous 2005 Lupi-type star V1118 Ori but contrasts large from erupting young V1647 2003 outbursts.