Fig 1: The secondary spetrum of J1518+4904. The top panel is measured at the orital phase 0.02, the bottom panel was measured at the phase of 0.51.

       By now we had observed this pulsar for several times. Because the eta value is also effected by the velocity of earth, we will elimate this erath effection by fitting an annual trending of the moudlation of arcs. Fig 2 shows such an effort to fitting the earth modulation. This result shows an improvement to the orginal measurenments with decresing the earth’s effection. We will get a more clear orital modulation arc by more observation in the future.

Fig2: The mesurements of the outer arc of J1518+4904. The dashed mesurements are the observation with inconspicuous scintillation. The left panel are the original arcs against the binary orbit. The middle panel shows the arcs and their observation time in a year. The red line here is the fitting annul modulation. The right panel are the arc with deducting the fitted annul modulation.