ASASSN-16oh is a peculiar transient supersoft X-ray source without mass-ejection signature in the field of the Small Magellanic Cloud .
Maccarone et al .
( 2019 ) concluded that ASASSN-16oh is the first dwarf nova with supersoft X-ray originated from an equatorial accretion belt on a white dwarf ( WD ) .
Hillman et al .
( 2019 ) proposed a thermonuclear runaway model that both the X-rays and V / I photons are emitted from the hot WD .
We calculated the same parameter models as Hillman et al. ’ s and found that they manipulated on/off the mass-accretion , and their best fit V light curves are 6 mag fainter , and decay about 10 times slower , than that of ASASSN-16oh .
We propose a nova model induced by high rate mass-accretion during a dwarf nova outburst , i.e. , the X-rays originate from a surface of the hydrogen-burning WD whereas the V / I photons from the irradiated disk .
Our model explains the main observational properties of ASASSN-16oh .
We also obtained thermonuclear runaway models with no-mass-ejection for a wide range of parameters of the WD mass and mass accretion rates including both natural and forced novae in low-metal environments of Z = 0.001 and Z = 0.0001 .
They are a new type of periodic supersoft X-ray sources with no-mass-ejection , and also a bright transient in V / I bands if they have a large disk .
We suggest that such objects are a candidate of type Ia supernova progenitors because its mass is increasing at a very high efficiency ( \sim 100 \% ) .