Rotational modulation of X-ray emission in orion nebula young stars

E. Flaccomio, G. Micela, S. Sciortino, E. D. Feigelson, W. Herbst, F. Favata, F. R. Harnden, S. D. Vrtilek

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We investigate the spatial distribution of X-ray-emitting plasma in a sample of young Orion Nebula Cluster stars by modulation of their X-ray light curves due to stellar rotation. The study, part of the Chandra Orion Ultradeep Project (COUP), is made possible by the exceptional length of the observation: 10 days of ACIS integration during a time span of 13 days, yielding a total of 1616 detected sources in the 17′ × 17′ field of view. We here focus on a subsample of 233 X-ray-bright stars with known rotational periods. We search for X-ray modulation using the Lomb Normalized Periodogram method. X-ray modulation related to the rotation period is detected in at least 23 stars with periods between 2 and 12 days and relative amplitudes ranging from 20% to 70%. In 16 cases, the X-ray modulation period is similar to the stellar rotation period, while in 7 cases it is about half that value, possibly due to the presence of X-ray-emitting structures at opposite stellar longitudes. These results constitute the largest sample of low-mass stars in which X-ray rotational modulation has been observed. The detection of rotational modulation indicates that the X-ray-emitting regions are distributed inhomogeneneously in longitude and do not extend to distances significantly larger than the stellar radius. Modulation is observed in stars with saturated activity levels (L X/L bol ∼ 10 -3) showing that saturation is not due to the filling of the stellar surface with X-ray-emitting regions.

Original languageEnglish (US)
Pages (from-to)450-468
Number of pages19
JournalAstrophysical Journal, Supplement Series
Issue number2
StatePublished - Oct 2005

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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