We analyze the wavelength-dependent variability of a sample of spectroscopically confirmed active galactic nuclei ( AGN ) selected from near-UV ( NUV ) variable sources in the GALEX Time Domain Survey that have a large amplitude of optical variability ( difference-flux S/N > 3 ) in the Pan-STARRS1 Medium Deep Survey ( PS1 MDS ) .
By matching GALEX and PS1 epochs in 5 bands ( NUV , g _ { P 1 } , r _ { P 1 } , i _ { P 1 } , z _ { P 1 } ) in time , and taking their flux difference , we create co-temporal difference-flux spectral energy distributions ( \Delta f SEDs ) using two chosen epochs for each of the 23 objects in our sample on timescales of about a year .

We confirm the ” bluer-when-brighter ” trend reported in previous studies , and measure a median spectral index of the \Delta f SEDs of \alpha _ { \lambda } = 2.1 that is consistent with an accretion disk spectrum .
We further fit the \Delta f SEDs of each source with a standard accretion disk model in which the accretion rate changes from one epoch to the other .
In our sample , 17 out of 23 ( \sim 74 % ) sources are well described by this variable accretion-rate disk model , with a median average characteristic disk temperature \bar { T } ^ { * } of 1.2 \times 10 ^ { 5 } K that is consistent with the temperatures expected given the distribution of accretion rates and black hole masses inferred for the sample .
Our analysis also shows that the variable accretion rate model is a better fit to the \Delta f SEDs than a simple power law .