We present eight new light curves of the transiting extra-solar planet HAT-P-25b obtained from 2013 to 2016 with three telescopes at two observatories .
We use the new light curves , along with recent literature material , to estimate the physical and orbital parameters of the transiting planet .
Specifically , we determine the mid-transit times ( T _ { C } ) and update the linear ephemeris , T _ { C [ 0 ] } =2456418.80996 \pm 0.00025 [ \mathrm { BJD } _ { \mathrm { TDB } } ] and P=3.65281572 \pm 0.00000095 days .
We carry out a search for transit timing variations ( TTVs ) , and find no significant TTV signal at the \Delta T = 80 s-level , placing a limit on the possible strength of planet-planet interactions ( \mathrm { TTV _ { G } } ) .
In the course of our analysis , we calculate the upper mass-limits of the potential nearby perturbers .
Near the 1:2 , 2:1 , and 3:1 resonances with HAT-P-25b , perturbers with masses greater than 0.5 , 0.3 , and 0.5 \mathrm { M _ { \earth } } respectively , can be excluded .
Furthermore , based on the analysis of TTVs caused by light travel time effect ( LTTE ) we also eliminate the possibility that a long-period perturber exists with M _ { p } > 3000 \mathrm { M _ { J } } within a = 11.2 { AU } of the parent star .