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Projeto Observacional para 2003A - P31
Autor: Raymundo Baptista
Título: Probing the X-Ray reprocessed light in the low-mass X-Ray binary X1822-371.
Resumo: The eclipsing low-mass X-ray binary (LMXB) X1822-371 is the prototype for a thick accretion disc with azimuthal structure (X-ray dips at phases 0.2 and 0.8). We propose simultaneous optical / X-ray observations of X1822-371 with sub-second time resolution in order to probe the X-ray reprocessing regions in the disc (~ 2 ligh-seconds size) and the companion star (~ 5 light-seconds distance). The optical "echoes" from the heated, inner-side of the companion star will enable us to measure the binary separation a and inclination i, thus providing the mass of the neutron star (new novel method). The optical "echoes" of the X-ray heating ths disc and mainly at the outer edge at phase 0.8 - where the largest azimuthal structure is caused by the impact of the gas stream - can provide the disc radius RD and its variation with azimuth. The X-ray observations will be made with RXTE. The simultaneous optical observations will be secured with the ESO 2.2m and the LNA 1.6m telescopes.