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

We present new high-resolution mid-infrared imaging, high-resolution opticalspectroscopy, and Chandra grating X-ray spectroscopy of the weak-lined T Tauristar DoAr 21. DoAr 21 (age < 10^6 yr and mass ~ 2.2 M_sun) is a strong X-rayemitter, with conflicting evidence in the literature about its disk properties.It shows weak but broad H-alpha emission; polarimetric variability; PAH and H2emission; and a strong, spatially-resolved 24-micron excess in archival Spitzerphotometry. Gemini sub-arcsecond-resolution 9--18 micron images show that thereis little or no excess mid-infrared emission within 100 AU of the star; theexcess emission is extended over several arcseconds, is quite asymmetric, andis bright in the UV-excited 11.3 micron PAH emission feature. A newhigh-resolution X-ray grating spectrum from Chandra shows that the stellarX-ray emission is very hard and dominated by continuum emission; it is well-fitby a multi-temperature thermal model and shows no evidence of unusually highdensities. We argue that the far-ultraviolet emission from the star'stransition region is sufficient to excite the observed extended PAH andcontinuum emission, and that the H2 emission may be similarly extended andexcited. This extended emission may be more akin to a small-scalephotodissociation region than a protoplanetary disk, highlighting both the veryyoung ages (< 10^6 yr) at which some stars are found without disks, and theextreme radiation environment around even late-type pre--main-sequence stars.

No Transition Disk? Infrared Excess, PAH, H2, and X-rays from the Weak-Lined T Tauri Star DoAr 21