========================================================================== J/AN/321/81 Orion Trapezium area ROSAT PSPC obs. II. (Lohmann+, 2000) The following files can be converted to FITS (extension .fit .fgz or .fiZ) table1.dat table2.dat ========================================================================== Query from: http://vizier.u-strasbg.fr/viz-bin/VizieR?-source=J/AN/321/81 ==========================================================================
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Beginning of ReadMe : J/AN/321/81 Orion Trapezium area ROSAT PSPC obs. II. (Lohother/mann+, 2000) ================================================================================ ROSAT PSPC observations of the Orion Trapezium area. II. Source variability and revised source list. Lohmann P., Wendker H.J. <Astron. Nachrichten, 321, 81 (2000)> =2000AN....321...81L ================================================================================ ADC_Keywords: Clusters, open ; X-ray sources ; Stars, pre-main sequence Mission_Name: ROSAT Keywords: open clusters and associations: general - open clusters and associations: individual (Orion OB1) - stars: activity - stars: pre-main sequence - X-rays Abstract: A deep ROSAT PSPC image centred on the Orion Trapezium has been reduced a second time using an improved version of the PSF to fit the data. The outer rim of the field of view was also included. The new catalogue contains 316 X-ray sources which are easily identified with pre-main sequence stars of the Ori OB1 Ic and Id association. All 316 sources were tested for variability. No variations were found inside the single exposures of about 45 minutes length each. Between the 4 exposures spaced over 5 days about 1/3 of the sources show signs of activities of various forms. As above 25% of these have somewhat regular lights curves (monotonically rising or falling or hill- shaped) we infer that at least some outbursts with time scales longer than a day are present and that past searches for X-ray flares of pre-main sequence stars were biased towards shorter time scales.