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K. Hamaguchi (NASA/GFSC), S. Yamauchi (Iwate University), K. Koyama (Kyoto University)
We observed a star forming field which contains the intermediate-mass young Herbig Ae/Be (HAeBe) star MWC297 using the ACIS instrument on the Chandra X-ray Observatory. In our 37 ksec observation we detect 18 X-ray sources above 4\sigma within the 9'\times17' ACIS field of view. Most sources are positionally correlated with J, K and H band sources detected in the 2MASS survey. The detected sources have net photon counts of between 10-100 counts. Six sources with more than 30 counts have large absorption columns of 1-6 \times1022 cm-2 and plasma temperatures approaching ~2 keV. The other weak sources are at least as hard as the six brightest sources, suggesting that all the detected sources are deeply embedded.
MWC297 exhibited a large X-ray flare reminiscent of low-mass stellar flares during an earlier ASCA observation (Hamaguchi et al. 2000). Identifying the flaring source with Chandra's pin-point spatial resolution is important to address whether HAeBes have magnetic activity similar to low-mass stars. Chandra detected an X-ray source at the position of MWC297, but the flux is a hundred times smaller than that expected from the ASCA observation. Assuming N\rm H ~2 \times1022 ergs s-1 converted from its AV, the X-ray luminosity is only 2\times1029 ergs s-1, corresponding to \log LX/Lbol ~8.8. This ratio is quite small when compared with other low-mass stars (which have \log LX/Lbol \lesssim -3) and even with normal OB stars driven by wind shocks (~7). We discuss reasons for the small X-ray luminosity.
Acknowledgement: This research is supported by the National Research Council.
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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.