Radiation Pressure Instability in the "turn-on" Changing-Look AGN SDSS J1430+2303
We aim to investigate the multi-wavelength variability, spectral, and timing properties of the changing-look active galactic nucleus (CL AGN) SDSS J1430+2303, and to explore the physical origin of its peculiar variability pattern that has not been observed before in other CL AGN. We perform a multi-wavelength analysis using optical, ultraviolet, and X-ray observations. We investigate the long-term optical color variation, characterize the evolution of the X-ray spectrum and timing properties, and construct broad-band spectral energy distributions to constrain the black hole mass, spin, and Eddington ratio. The optical flux increased by an order of magnitude over four years, accompanied by a spectral transition from Seyfert 1.9 to 1.2. The long-term color variation follows the ``bluer-when-brighter'' trend, with a color-magnitude slope consistent with previous statistical results for CL and Type 1 AGNs. During the brightened high state, the optical, ultraviolet, and X-ray light curves exhibited rapid decaying periods with progressively decreasing amplitudes, a behavior not previously reported in other CL AGNs. X-ray spectral analysis reveals a remarkably weak soft excess that declines more steeply than the hard X-rays as the total luminosity decreases. X-ray timing analysis shows a nearly constant break frequency and a hard lag at $\sim10^{-4}$ Hz during the luminosity decline, suggesting a stable disk--corona geometry. Broad-band spectral energy distribution fitting constrains the black hole mass to $M_{\rm BH}=3.8-19.5\times10^7\,M_\odot$ and favors a high spin ($a\gtrsim0.77$), while the correspondingly low Eddington ratio can account for the observed weak soft excess. We propose that the observed multi-wavelength decaying periods and their progressively decreasing amplitudes are associated with a shrinking unstable zone driven by radiation-pressure instability in the accretion disk.