Long-term photometric behaviour of the eclipsing Z Cam-type dwarf nova
  AY Psc
  New eclipse timings of the Z Cam-type dwarf nova AY Psc were measured and the
orbital ephemeris was revised. Based on the long-term AAVSO data, moreover, the
outburst behaviors were also explored. Our analysis suggests that the normal
outbursts are quasi-periodic, with an amplitude of $\sim2.5(\pm0.1)$ mag and a
period of $\sim18.3(\pm0.7)$ days. The amplitude vs. recurrence-time relation
of AY Psc is discussed, and we concluded that this relation may represents
general properties of dwarf nova (DN) outbursts. The observed standstill ends
with an outburst, which is inconsistent with the general picture of Z Cam-type
stars. This unusual behavior was considered to be related to the mass-transfer
outbursts. Moreover, the average luminosity is brighter during standstills than
during outburst cycles. The changes in brightness marks the variations in
$\dot{M}_{2}$ due to the disc of AY Psc is nearly steady state. $\dot{M}_{2}$
value was limited to the range from $6.35\times10^{-9}$ to
$1.18\times10^{-8}M_{\odot}yr^{-1}$. More detailed examination shows that there
are a few small outbursts presence during standstills. These events with
amplitudes of $\sim0.5-0.9$ mag are very similar to the stunted outbursts
reported in some NLs. We discussed several possible mechanisms and suggested
that the most reasonable mechanism for these stunted outbursts is a changing
mass-transfer rate.
