An X-ray outburst from the rapidly accreting young star that illuminates McNeil's Nebula

Abstract

Young, low-mass stars are luminous X-ray sources1 whose powerful X-ray flares^(2-6) may exert a profound influence over the process of planet formation^(7). The origin of such emission is uncertain. Although many or perhaps most recently formed, low-mass stars emit X-rays as a consequence of solar-like coronal activity^(1,8,9), it has also been suggested that X-ray emission may be a direct result of mass accretion onto the forming star^(10-12). Here we report X-ray imaging spectroscopy observations which reveal a factor ~50 increase in the X-ray flux from a young star that is presently undergoing a spectacular optical/IR outburst^(13,14). The outburst is thought to be due to the sudden onset of a phase of rapid accretion^(14-16). The coincidence of a surge in X-ray brightness with the optical/IR eruption demonstrates that strongly enhanced high-energy emission from young stars can occur as a consequence of high accretion rates. We 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 accretion flood (Refer to PDF file for exact formulas).