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Magnetic activities on young stars

Abstract

Almost all young stellar objects (YSOs) are now known to emit X-rays driven by the magnetic activity. The solar-type dynamo is the plausible mechanism to generate the magnetic fields, but it does not work properly on protostars or intermediate-mass YSOs due to the difference of their stellar inner structure. To find an alternative mechanism, the structure and energy of magnetic fields surrounding stars should be investigated. In this sence, a stellar X-ray flare gives us important information because it directly traces an activity of one magnetic loop. With this motivation, we searched for stellar X-ray flares using the ASCA satellite and detected seven flares from low-mass and intermediate-mass YSOs. By comparing flare parameters with the absorption column density (NH), we found that younger stars tend to have higher plasma temperature and larger emitting volumes. Furthermore, the flare loop size should be far larger than the solar radii in low-mass protostars and Herbig Ae/Be stars (HAEBEs). These facts suggest that the magnetic fields of low-mass protostars and HAEBEs far extend from the stellar main body and probably connect to the circumstellar disks, and that the magnetic reconnection by the star-disk differential rotation should energize the X-ray flares. We also present supporting evidence of quasi-periodic flares detected on the ClassI protostar YLW15.

References

  1. Hamaguchi, K., H. Terada, A. Bamba, and K. Koyama, Large X-ray flare from the Herbig Be star MWC 297, ApJ, 532, 1111, 2000.

  2. Kamata, Y., K. Koyama, Y. Tsuboi, and S. Yamauchi, X-ray analysis of the ρ Ophiuchi dark cloud with ASCA: Source identification, X-ray spectra, and temporal variability, PASJ, 49, 461, 1997.

  3. Koyama, K., K. Hamaguchi, S. Ueno, N. Kobayashi, and E. D. Feigelson, Discovery of hard X-rays from a cluster of protostars, PASJ, 48, L87, 1996.

  4. Montmerle, T., L. Koch-Miramond, E. Falgarone, and J. E. Grindlay, Einstein observations of the Rho Ophiuchi dark cloud—an X-ray christmas tree, ApJ, 269, 182, 1983.

  5. Montmerle, T., N. Grosso, Y. Tsuboi, and K. Koyama, Rotation and X-ray emission from protostars, ApJ, 532, 1097, 2000.

  6. Ozawa, H., F. Nagase, Y. Ueda, T. Dotani, and M. Ishida, Detection of hard X-rays from a class I protostar in the HH 24–26 region in the Orion molecular cloud, ApJ letter, 523, L81, 1999.

  7. Schmitt, J. H. M. M. and F. Favata, Continuous heating of a giant X-ray flare on Algol, Nature, 401, 44, 1999.

  8. Skinner, S. L. and F. M. Walter, ASCA observations of the T Tauri star SU Aurigae and the surrounding L1517 dark cloud, ApJ, 509, 761, 1998.

  9. Skinner, S. L. and S. Yamauchi, ASCA observations of HD 104237 (A4e) and the origin of X-ray emission from Herbig Ae stars, ApJ, 471, 987, 1996.

  10. Tsuboi, Y., K. Koyama, H. Murakami, M. Hayashi, S. Skinner, and S. Ueno, ASCA detectionofasuperhot 100 million KX-rayflare onthe weak-lined T Tauri star V773 Tauri, ApJ, 503, 894, 1998.

  11. Tsuboi, Y., K. Imanishi, K. Koyama, N. Grosso, and T. Montmerle, Quasi-periodic X-ray flares from the protostar YLW 15, ApJ, 532, 1089, 2000.

  12. Yamauchi, S., K. Hamaguchi, K. Koyama, and H. Murakami, ASCA observations of the Chamaeleon II dark cloud, PASJ, 50, 465, 1998.

  13. Zinnecker, H. and Th. Preibisch, X-ray emission from Herbig Ae/Be stars: A ROSAT survey, A&A, 292, 152, 1994.

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Correspondence to Kenji Hamaguchi.

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Hamaguchi, K., Tsuboi, Y., Imanishi, K. et al. Magnetic activities on young stars. Earth Planet Sp 53, 683–687 (2001). https://doi.org/10.1186/BF03353289

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Keywords

  • Molecular Cloud
  • Magnetic Activity
  • Stellar Wind
  • Young Star
  • Circumstellar Disk