We present the results of precision timing observations of the binary millisecond pulsar ( catalog PSR J1640+2224 ) .
Combining the pulse arrival time measurements made with the Effelsberg 100-m radio telescope and the Arecibo 305-m radio telescope , we have extended the existing timing model of the pulsar to search for a presence of the effect of a general-relativistic Shapiro delay in the data .
At the currently attainable precision level , the observed amplitude of the effect constrains the companion mass to m _ { 2 } = 0.15 ^ { +0.08 } _ { -0.05 } M _ { \sun } , which is consistent with the estimates obtained from optical observations of the white dwarf companion and with the mass range predicted by theories of binary evolution .
The measured shape of the Shapiro delay curve restricts the range of possible orbital inclinations of the PSR J1640+2224 system to 78 ^ { \circ } \leq i \leq 88 ^ { \circ } .
The pulsar offers excellent prospects to significantly tighten these constraints in the near future .