I read that photon bunching happens for thermal light within the coherence time of the thermal light. That is, if the time for detection is greater than the coherence time of the thermal light, no bunching is observed.
I also read that atoms of Bose-Einstein condensates are randomly bunched, but they become bunched if they are heated above the critical temperature, and they are bunched only within the coherence length of the matter wave.
Sources: http://www.sciencealert.com/cold-atoms-act-like-laser-beam https://physics.anu.edu.au/news.php?NewsID=13 http://www.abc.net.au/science/articles/2011/02/25/3149175.htm?site=indepthfeature&topic=latest http://phys.org/news/2011-02-scientists-atoms-lasers.html
Does this also hold for the Hong-ou-Mandel effect? Do the photons bunch at the same output of the beam splitter only if they arrive together at the beamsplitter within the coherence time?