T Coronae Borealis Photometry Project

T Coronae Borealis (T CrB) is a recurrent nova. This is a type of star that experiences periodic increases in brightness. Novas were noted in 1217 (suspected), 1787 (suspected), 1866, and 1946, demonstrating an 80 year periodicity. The star itself is a binary system that displays its own intensity variation around magnitude 10 due to the 228 day orbit of the red giant and white dwarf components around each other.

The two stars orbit very closely, and material from the red giant is drawn off its surface and deposits onto the white dwarf. When enough material accumulates, it briefly undergoes nuclear fusion, and the magnitude of the system can reach about magnitude 2, some 1500 times brighter than the normal state, and bright enough to become a naked eye star. This intensity spike only lasts a few days.

A slight brightening was detected in 2015, followed by dimming into 2023, that was similar to observations from 1938-1945. If this were an indication of an approaching nova, we'd expect it to occur sometime in 2024. So far, no nova has happened, but it could happen anytime. I've been recording the brightness of this star on most clear nights since July 2024.

I image the star through red, green, and blue filters. To avoid saturating the detector (because the star is bright) I take only 10-second exposures. Depending on conditions I collect from a few tens of images to a few hundred, and average my measurements. This is an RGB image of the field made from a stack of RGB subexposures adding up to a few minutes total exposure time.

This is the light curve over the period I've been collecting data. Smaller magnitude values represent brighter measurements. The underlying 228 day periodicity is apparent. This data set is just coming up on one full cycle.