AK Sco, first detection of a highly disturbed atmosphere in a pre-main sequence close binary

Abstract

AK Sco is a unique source: a ~10 Myrs old pre-main sequence spectroscopic binary composed of two nearly equal F5 stars that at periastron are separated by barely eleven stellar radii so, the stellar magnetospheres fill the Roche lobe at periastron. The orbit is not yet circularized (e=0.47) and very strong tides are expected. This makes of AK Sco, the ideal laboratory to study the effect of gravitational tides in the stellar magnetic field building up during pre-main sequence (PMS) evolution. In this letter, the detection of a highly disturbed (sigma ~ 100 km/s) and very dense atmosphere (ne = 1.6e10cm-3) is reported. Significant line broadening blurs any signs of ion belts or bow shocks in the spectrum of the atmospheric plasma. The radiative loses cannot be accounted solely by the dissipation of energy from the tidal wave propagating in the stellar atmosphere; neither by the accreting material. The release of internal energy from the star seems to be the most likely source of the plasma heating. This is the first clear indication of a highly disturbed atmosphere surrounding a pre-main sequence close binary.

10 pages 2 figures. Astrophysical Journal Letters, accepted

References in corpus (6)

• The Magnetic Fields of Classical T Tauri Stars
• Ultraviolet Extinction Properties in the Milky Way
• On the origin of the X-ray emission from Herbig Ae/Be stars
• Evidence for stellar driven outflows from the Classical T Tauri star RY Tau
• The formation of planetary disks and winds: an ultraviolet view
• Polarimetric variations of binary stars. VI. Orbit-induced variations in the pre-main-sequence binary AK Sco

Cited by in corpus (13)

• A Hubble Space Telescope Survey of H2 Emission in the Circumstellar Environments of Young Stars
• Hot Gas Lines in T Tauri Stars
• Kuiper Belts Around Nearby Stars
• Direct Measurement of Interstellar Extinction Toward Young Stars Using Atomic Hydrogen Lyman-$\alpha$ Absorption
• The 1600 Angstrom Emission Bump in Protoplanetary Disks: A Spectral Signature of H${}_2$O Dissociation
• XMM-Newton monitoring of the close pre-main-sequence binary AK Sco. Evidence of tide driven filling of the inner gap in the circumbinary disk
• A GALEX based search for the sparse young stellar population in the Taurus-Aurigae star forming region
• Deep XMM-Newton observation of the Eta Chamaleontis cluster
• Constraints to the magnetospheric properties of T Tauri stars - II. The Mg II ultraviolet feature
• Signatures of Hot Molecular Hydrogen Absorption from Protoplanetary Disks: I. Non-thermal Populations
• Protoplanetary disk shadowing by gas infalling onto the young star AK Sco
• Accretion and inter-cycle variations in the PMS interacting binary AK Sco
• Evidence of a Disk-wind Origin for Fluorescent H${}_2$ in Classical T Tauri Stars