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 Tools annual

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 monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

We seek to find the precursors of the Herbig Ae/Be stars in the solarvicinity within 500 pc from the Sun. We do this by creating an opticallyselected sample of intermediate mass T-Tauri stars (IMTT stars) here defined asstars of masses $1.5 M_{\odot}\leq M_* \leq 5 M_{\odot}$ and spectral typebetween F and K3, from literature. We use literature optical photometry(0.4-1.25$\mu$m) and distances determined from Gaia DR2 parallax measurementstogether with Kurucz stellar model spectra to place the stars in a HR-diagram.With Siess evolutionary tracks we identify intermediate mass T-Tauri stars fromliterature and derive masses and ages. We use Spitzer spectra to classify thedisks around the stars into Meeus Group I and Group II disks based on their[F$_{30}$/F$_{13.5}$] spectral index. We also examine the 10$\mu$m silicatedust grain emission and identify emission from Polycyclic Aromatic Hydrocarbons(PAH). From this we build a qualitative picture of the disks around theintermediate mass T-Tauri stars and compare this with available spatiallyresolved images at infrared and at sub-millimeter wavelengths to confirm ourclassification. We find 49 intermediate mass T-Tauri stars with infraredexcess. The identified disks are similar to the older Herbig Ae/Be stars indisk geometries and silicate dust grain population. Spatially resolved imagesat infra-red and sub-mm wavelengths suggest gaps and spirals are also presentaround the younger precursors to the Herbig Ae/Be stars. Comparing thetimescale of stellar evolution towards the main sequence and current models ofprotoplanetary disk evolution the similarity between Herbig Ae/Be stars and theintermediate mass T-Tauri stars points towards an evolution of Group I andGroup II disks that are disconnected, and that they represent two differentevolutionary paths.

What happened before? -- The disks around the precursors of young Herbig Ae/Be stars