XMM-Newton X-Ray Observations of LkCa 15: A T Tauri Star with a Formative Planetary System

Autor(en): Stephen Lee Skinner, Manuel Güdel
Abstrakt: High-resolution ground-based images of the T Tauri star LkCa 15 have revealed multiple companions that are thought to comprise a formative planetary system. The candidate protoplanets orbit at distances of ˜15-20 au within the dust-depleted inner region of the circumstellar disk. Because of its young age (˜1-4 Myr), LkCa 15 provides a benchmark system for testing planet-formation models. We detected LkCa 15 as a bright X-ray source in a short 10 ks Chandra observation in 2009. We report here new results obtained from a deeper 37 ks XMM-Newton observation in 2014. The new data provide better sampling in the time domain and improved sensitivity at low energies below 1 keV. Spectral fits with thermal emission models require at least two temperature components at kT_cool ≈ 0.4 keV and kT_hot ≈ 2.2 keV. The value of kT_hot is about a factor of two less than inferred from Chandra, suggesting that the hot-component temperature is variable. The best-fit absorption column density is in good agreement with that expected from optical extinction estimates {A}{{V}} ≈ 1.3-1.7 mag. The intrinsic X-ray luminosity is L x (0.2-10 keV) = 3 × 10³⁰ erg s^-1. Estimates of the X-ray heating rate of the inner disk and protoplanets are sensitive to the assumed disk gas surface density for which recent ALMA observations give estimates Σ_0,gas ~ 10² g cm^-2 at 1 au from the star. At such densities, X-ray heating is confined mainly to the upper disk layers and X-ray penetration through the disk midplane to the protoplanets at r ≈ 15-20 au is negligible.
Organisation(en): Institut für Astrophysik
Externe Organisation(en): University of Colorado, Boulder
Journal: The Astrophysical Journal
Band: 839
Anzahl der Seiten: 8
ISSN: 0004-637X
DOI: https://doi.org/10.3847/1538-4357/aa67ec
Publikationsdatum: 04-2017
Peer-reviewed: Ja
ÖFOS 2012: 103003 Astronomie, 103004 Astrophysik
Schlagwörter
ASJC Scopus Sachgebiete: Astronomy and Astrophysics, Space and Planetary Science
Link zum Portal: https://ucrisportal.univie.ac.at/de/publications/9a4c887f-8265-49e9-840f-d14b86920b2d

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