[2] It became well known when it was reported to have the largest core ever observed in a galaxy, spanning some 15,000 light years,[2] however this was subsequently refuted.

Previous estimates by Lauer et al. have jointed a mass value as high as 310 billion M☉[1][2] using the gamma ray point break radius method.

[2] The paper by Lopez-Cruz et al. stated:[2] "Therefore, we conservatively suggest that Holm 15A hosts an SMBH with a mass of ~1×1010 M☉."

Kormendy and Ho et al derived these equations using the M–sigma relation and the size of the outer bulge of the galaxy, which are indirect estimates.

Rusli et al derived a value of 170 billion M☉ using break radius methodology.