Chandra
Orion Ultradeep Project
Big flares
Above is a one of the more
powerful flares with peak luminosity reaching 2x1032 erg/s, far above contemporary
solar levels. It shows the classic flare behavior seen in the Sun and
other magnetically active stars: a fast rise to high temperatures produced
by the violent magnetic reconnection event, followed by a slower decay in
both intensity and temperature as the plasma cools.
To the right, we see the results of detailed analysis of the spectral evolution during the decay phase of this flare. The top graph shows that, as it cooled from 150 MK to 30 MK, the density dropped by a factor of 2-3. The bottom graph shows that the plasma cooled in about 3 hours. We use these results in a model of a cylindrical magnetic loop to estimate the loop length: in this case, we derive 4 R* or 4 times the size of the star. Other cases with slower decays give 10-20 R*.
These are much larger loops than seen in even the most magnetically active older star! They are probably too large to be stable, particularly to centrifugal forces as the star rotates. We conclude that we may be seeing magnetic loops which extend from the star to the inner edge of a protoplanetary disk. Theory has predicted the existence of such large magnetic structures.
The full paper on COUP big flares is:
Bright X-ray flares in Orion young stars from COUP: evidence for star-disk magnetic elds?
F. Favata, E. Flaccomio, F. Reale, G. Micela, S. Sciortino, H. Shang, K. G. Stassun, E. D. Feigelson
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Big flares
To the right, we see the results of detailed analysis of the spectral evolution during the decay phase of this flare. The top graph shows that, as it cooled from 150 MK to 30 MK, the density dropped by a factor of 2-3. The bottom graph shows that the plasma cooled in about 3 hours. We use these results in a model of a cylindrical magnetic loop to estimate the loop length: in this case, we derive 4 R* or 4 times the size of the star. Other cases with slower decays give 10-20 R*.
These are much larger loops than seen in even the most magnetically active older star! They are probably too large to be stable, particularly to centrifugal forces as the star rotates. We conclude that we may be seeing magnetic loops which extend from the star to the inner edge of a protoplanetary disk. Theory has predicted the existence of such large magnetic structures.
The full paper on COUP big flares is:
Bright X-ray flares in Orion young stars from COUP: evidence for star-disk magnetic elds?
F. Favata, E. Flaccomio, F. Reale, G. Micela, S. Sciortino, H. Shang, K. G. Stassun, E. D. Feigelson
Back to the COUP home page