Observations of X-ray emission from T Tauri stars

Abstract

Observations of 28 T Tauri stars with the Imaging Proportional Counter on board the Einstein (HEAO 2) X-ray Observatory are reported. Eight are detected with soft X-ray luminosities of approximately 10 to the 30th ergs/sec in the Taurus cloud and approximately 10 to the 31st ergs/sec in the Orion cloud. One star, DG Tauri, is found to be highly variable, increasing in brightness by an order of magnitude in 35 minutes, with a significant rise within 4 minutes. Theoretical considerations indicate the X-rays are not produced in the entire envelope emitting the hydrogen Balmer lines, and the rapid variability suggests the emission occurs close to the photosphere rather than far from the star.