X-Ray Outburst from the Rapidly Accreting Young Star that Illuminates McNeil's Nebula

摘要

Young, low-mass stars are luminous X-ray sources whose powerful X-ray flares may exert a profound influence over the process of planet formation. The origin of the X-ray emission is uncertain. Although many (or perhaps most) recently formed, low-mass stars emit X-rays as a consequence of solar-like coronal activity, it also has been suggested that X-ray emission may be a direct result of mass accretion onto the forming star. The authors report on X-ray imaging spectroscopy observations that reveal a factor (caret)50 increase in the X-ray flux from a young star that is at present undergoing a spectacular optical/ infrared outburst (this star illuminates McNeil's nebula). The outburst seems to be due to the sudden onset of a phase of rapid accretion. The coincidence of a surge in X-ray brightness with the optical/infrared eruption demonstrates that strongly enhanced high-energy emission from young stars can occur as a consequence of high accretion rates. The authors suggest that such accretion- enhanced X-ray emission from erupting young stars may be short-lived, because intense star disk magnetospheric interactions are quenched rapidly by the subsequent flood of new material onto the star. (1 table, 3 figures, 30 refs.).