The evolution of inner disk radius with orbital phase in Circinus X-1

Using RXTE observations, we investigate the evolution of inner disk radius R_in of Cir X-1 during two cycles and find obvious orbital modulation. We argue that the modulation is attributed to its high orbital eccentricity. The disk luminosity is inversely with the inner disk temperature kT_in, which is ascribed to the slow increase of kT_in and, however, the rapid decrease of R_in during the passage for the neutron star to depart from the companion star.