A Simultaneous Optical and X-ray Variability Study of the Orion Nebula Cluster. I. Incidence of Time-Correlated X-ray/Optical Variations

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dc.creatorStassun, Keivan G.
dc.creatorBerg, M. van den
dc.creatorFeigelson, Eric
dc.creatorFlaccomio, Ettore
dc.date2006-06-04
dc.date.accessioned2026-07-07T10:39:11Z
dc.date.available2026-07-07T10:39:11Z
dc.descriptionWe present a database of $BVRI$ time-series photometry of the Orion Nebula Cluster obtained with two ground-based telescopes at different longitudes to provide simultaneous coverage with the 13-d Chandra observation of the cluster. The resulting database of simultaneous optical and X-ray light curves for some 800 pre--main-sequence (PMS) stars represents, by a factor of hundreds, the largest synoptic, multi--wavelength-regime, time-series study of young stars to date. This database will permit detailed analyses of the relationship between optical and X-ray variability among a statistically significant ensemble of PMS stars, with the goal of elucidating the origins of PMS X-ray production. In this first paper, we present the optical observations, describe the combined X-ray/optical database, and perform an analysis of time-correlated variability in the optical and X-ray light curves. We identify 40 stars (representing 5% of our study sample) with possible time-correlated optical and X-ray variability. Examples of both positive and negative time-correlations are found, possibly representing X-ray flares and persistent coronal features associated with both cool and hot surface spots (i.e. magnetically active regions and accretion shocks). We also find two possible examples of "white-light" flares coincident with X-ray flares; these may correspond to the impulsive heating phase in solar-analog flares. However, though interesting, these represent unusual cases. More generally, we find very little evidence to suggest a direct causal link between the sources of optical and X-ray variability in PMS stars. The conclusion that accretion is a primary driver of X-ray production in PMS stars is not supported by our findings.
dc.description69 pages, 46 figures, accepted by ApJ
dc.identifierhttps://arxiv.org/abs/astro-ph/0606079
dc.identifierhttp://arxiv.org/abs/astro-ph/0606079
dc.identifierAstrophys.J.649:914-926,2006
dc.identifierdoi:10.1086/506422
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/180938
dc.subjectAstrophysics
dc.titleA Simultaneous Optical and X-ray Variability Study of the Orion Nebula Cluster. I. Incidence of Time-Correlated X-ray/Optical Variations
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