English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

EX Lupi is the prototype for a class of young, pre-main sequence stars whichare observed to undergo irregular, presumably accretion-generated, opticaloutbursts that result in a several magnitude rise of the optical flux. EX Lupiwas observed to optically erupt in 2008 January, triggering Chandra ACIS ToOobservations shortly thereafter. We find very strong evidence that most of theX-ray emission in the first few months after the optical outburst is generatedby accretion of circumstellar material onto the stellar photosphere.Specifically, we find a strong correlation between the decreasing optical andX-ray fluxes following the peak of the outburst in the optical, which suggeststhat these observed declines in both the optical and X-ray fluxes are theresult of declining accretion rate. In addition, in our models of the X-rayspectrum, we find strong evidence for a ~0.4 keV plasma component, as expectedfor accretion shocks on low-mass, pre-main sequence stars. From 2008 Marchthrough October, this cool plasma component appears to fade as EX Lupi returnsto its quiescent level in the optical, consistent with a decrease in theoverall emission measure of accretion shock-generated plasma. The overall smallincrease of the X-ray flux during the optical outburst of EX Lupi is similar towhat was observed in previous X-ray observations of the 2005 optical outburstof the EX Lupi-type star V1118 Ori but contrasts with the large increase of theX-ray flux from the erupting young star V1647 Ori during its 2003 and 2008optical outbursts.

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