X-ray Irradiation of the LkCa 15 Protoplanetary Disk

TL;DR

This study detects X-ray emission from the LkCa 15 protoplanetary disk, providing initial estimates of X-ray ionization and heating rates crucial for understanding physical conditions in planet-forming regions.

Contribution

It presents the first detection of X-ray emission from LkCa 15 and estimates its impact on disk ionization and heating, advancing models of planet-forming disks.

Findings

LkCa 15 is a bright X-ray source with two plasma components.

X-ray properties enable estimates of ionization and heating rates.

Results serve as a basis for more realistic disk modeling.

Abstract

LkCa 15 in the Taurus star-forming region has recently gained attention as the first accreting T Tauri star likely to host a young protoplanet. High spatial resolution infrared observations have detected the suspected protoplanet within a dust-depleted inner gap of the LkCa 15 transition disk at a distance of 15 AU from the star. If this object's status as a protoplanet is confirmed, LkCa 15 will serve as a unique laboratory for constraining physical conditions within a planet-forming disk. Previous models of the LkCa 15 disk have accounted for disk heating by the stellar photosphere but have ignored the potential importance of X-ray ionization and heating. We report here the detection of LkCa 15 as a bright X-ray source with Chandra. The X-ray emission is characterized by a cool heavily-absorbed plasma component at kT_cool ~0.3 keV and a harder component at kT_hot ~5 keV. We use the observed X-ray properties to provide initial estimates of the X-ray ionization and heating rates within the tenuous inner disk. These estimates and the observed X-ray properties of LkCa 15 can be used as a starting point for developing more realistic disk models of this benchmark system.