Young, low-mass stars are luminous X-ray sources1 whose powerful X-ray flares2,3,4,5,6 may exert a profound influence over the process of planet formation7. 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 activity1,8,9, it has also been suggested that X-ray emission may be a direct result of mass accretion onto the forming star10,11,12. 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 at present undergoing a spectacular optical/infrared outburst13 (this star illuminates McNeil's nebula14). The outburst seems to be due to the sudden onset of a phase of rapid accretion13,15,16. 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. 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 flood of new material onto the star.
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CXO observations of the erupting object in L1630 acquired in March 2004 were obtained under allocations of CXC Director's Discretionary Time. XSPEC software is maintained by NASA's High Energy Astrophysics Science Archive Research Center. The archival optical image in Fig. 2 was obtained with ESO's VLT at the Paranal Observatories under program ID 272.C-5045. We thank B. L. Gary for communicating results of I-band monitoring of the source.
The authors declare that they have no competing financial interests.
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Kastner, J., Richmond, M., Grosso, N. et al. An X-ray outburst from the rapidly accreting young star that illuminates McNeil's nebula. Nature 430, 429–431 (2004). https://doi.org/10.1038/nature02747