[raattgift]

> AFAIK, only supermassive black holes at the center of galaxies have disks of material that is falling inward

Stellar binaries are extremely common, and there is a reasonably large supply of binarys where one star has become a compact object. Their companion stars often drop lots of matter onto them, resulting in a reasonable supply of black holes. Diskoseismologists and others working on Swift have catalogued hundreds of stellar mass black hole accretion disks.

Examples from Swift:

http://adsabs.harvard.edu/abs/2013ApJ...769...16R https://arxiv.org/abs/1112.2249 (preprint version)

Swift also spotted ASASSN-14li which was a star being shredded by an SMBH and forming an early accretion structure. The event has been followed up by other observatories (notably Chandra and the European very long baseline interferometry network). ASASSN-14li is an easy google search term (the trick is knowing the term in the first place :-) ), hopefully you will enjoy some of the hits. :-)

[dwaltrip]

Ah, interesting. That makes a lot of sense. Would it be correct to say that if both objects in a binary pair are SMBHs, they would very likely not have an accretion disk, as the companion would be unable to send over any material?

[raattgift]

> if both objects in a binary pair are SMBHs, they would very likely not have an accretion disk, as the companion would be unable to send over any material

BH's don't let what's in the horizon out unless outside is verrrrrrrrrrrry cold (the universe will have to keep expanding for a long tine before it's cold enough for even isolated stellar-mass BHs to lose net mass to evaporation) or the BH is very small.

On the other hand, SMBHs will typically be found in galactic centres, where there is a lot of dust and gas.

So each of the mutually orbiting SMBHs may well have a substantial accretion disk. They may interact, or they might not (the disks might not be in the same plane, for instance).

Given the number of intensely active galactic nuclei we see in the sky, I don't think it's terribly unlikely for a central black hole to have an enormous accretion disk.

However, the Milky Way doesn't have an active galactic nucleus the central parsec is relatively quiet. The dense object in the central parsec is also pretty low-mass compared to that in many galaxies. https://www-xray.ast.cam.ac.uk/xray_introduction/AGN_intro.h...

[dwaltrip]

Hmmm. I wouldn't have guessed that! I suppose it does make sense that SMBHs in galactic centers could have relatively significant accretion disks. Thanks for the informative response.