The other tool used by astrophysicists is a lightcurve which is a graph of the total number of photons (or the total number of photons in a certain energy range) as a function of time.
The most important information that a lightcurve can give is whether the number of photons from a source is changing over time. If it is changing, we might also be able to tell if those changes are cyclic, which can constrain some of the source's properties.
For example, if the source is changing in a cyclic manner, then the change is likely from either the rotation of the source itself or something in orbit around the source, since the rotation (or orbit) occurs regularly with a period that is not likely to change by much.
Here is a lightcurve I made of XTE (an X-ray telescope) data from an active galactic nucleus (covered in the AGN section). The source seems to have a high state (lots of photons) followed by a low state and another high state, which are labeled in the plot by S3, S4 and S5, respectively.