We analyze the latest \emph{Suzaku} observation of the bright neutron star
low-mass X-ray binary Serpens X-1 taken in 2013 October and 2014 April. The
observation was taken using the burst mode and only suffered mild pile-up
effects. A broad iron line is clearly detected in the X-ray spectrum. We test
different models and find that the iron line is asymmetric and best interpreted
by relativistic reflection. The relativistically broadened iron line is
generally believed to originate from the innermost regions of the accretion
disk, where strong gravity causes a series of special and general relativistic
effects. The iron line profile indicates an inner radius of ∼8RG​, which gives an upper limit on the size of the neutron star. The asymmetric
iron line has been observed in a number of previous observations, which gives
several inner radius measurements at different flux states. We find that the
inner radius of Serpens X-1 does not evolve significantly over the range of
L/LEdd​∼0.4−0.6, and the lack of flux dependence of the inner radius
implies that the accretion disk may be truncated outside the innermost stable
circular orbit by the boundary layer rather than the stellar magnetic field.Comment: 8 pages, 6 figures, accepted for publication in Ap