Detection of hard X-rays from a class 1 protostar in HH 24-26 region

Abstract

The HH24-26 region in the L1630 Orion molecular cloud with was observed the X-ray observatory ASCA (Advanced Satellite for Cosmology and Astrophysics) in the 0.5 - 10 keV band. X-ray emission was detected from the Class 1 protostar SSV63E + W and the T Tauri star SSV61. The spectra of both SSV63E + W and SSV61 are well explained by a thermal plasma model of high and low temperatures, respectively. An evidence that the protostar SSV63E + W is embedded deeply in the surrounding dust envelope was obtained. The X-ray light curve of SSV63E + W showed an X-ray flare during the observation. The 0.5 - 10 keV luminosity of SSV63E + W was about 1 x 10(exp 32) erg s per sec in the quiescent state. Present detection of hard X-rays from SSV63E + W is remarkable, because this is the first X-ray detection of a protostar in Orion.

L1630オリオン座分子雲にあるHH24-26領域の、0.5から10keV帯でのX線天文台あすか(Advanced Satellite for Cosmology and Astrophysics)による観測を行なった。クラス1原始星SSV63E+WおよびTタウリ型星SSV61からのX線を検出した。SSV63E+WおよびSSV61のスペクトルはそれぞれ、高温および低温の熱的プラズマモデルでよく説明できる。原始星SSV63E+Wはダスト外層に深く埋もれているという証拠を得た。SSV63E+WのX線光度曲線は観測中に生じたX線フレアを示している。SSV63E+Wの0.5-10keV帯での光度は静穏期で1×10(exp 32)erg/sであった。今回のSSV63E+WのX線検出は、オリオン領域の原始星からX線を検出した最初の例であり、注目に値する。