4 ms·
LIGO also searches for BH/NS mergers and for NS/NS mergers. None have been announced yet, but they are definitely something we look for. BH/NS and NS/NS merger
by stefco_ 9y ago
LIGO also searches for BH/NS mergers and for NS/NS mergers. None have been announced yet, but they are definitely something we look for.
BH/NS and NS/NS mergers are exciting because they involve conventional matter and are likely to give off neutrinos and light as well as GWs. This means that EM followup is more likely to be worthwhile.
The smaller mass of neutron stars means they are more common, and the NS event-rate is expected to be much higher than the BH event rate. But BH events are louder due to the extra mass, so we can search in a much much larger volume of space, which so far has been favorable for BBH (binary black hole) merger detections.
Another interesting thing about BNS mergers is that, because they get closer/faster before merging, their signal should climb to higher frequencies and spends much, much longer in our sensitive band than BBH mergers (this is also true for lighter BBH mergers vs. heavier ones). This is really cool because it means that BNS mergers can be fit much more tightly to model waveforms, allowing for more precise parameter estimation (among other things) given the same peak signal-to-noise ratio.
- nerfhammer 9y agoNS-NS collision, everything doesn't disappear into an event horizon, wouldn't they deform and maybe some mass gets ejected, so would the impact event sound more complex/irregular? It would be cool if we could hear a NS-NS collision of sufficient masses such that we could hear a BH being born for the first time. Will we reasonably ever hear a supermassive BH collision? I would assume their loudness to rarity ratio is just too low.
- ssijak 9y agoHow cool would be to be bale to see a video of that merger? One can only dream..
- stefco_ 9y agoThese gorgeous, physically-correct simulations are about as close as you'll get for now: https://www.black-holes.org/explore/movies https://www.black-holes.org/explore/movies
- stefco_ 9y agoOne problem is that supermassive BHs merge at very low frequencies; they merge before their orbits get fast. LIGO's sensitivity range is in about the same range of frequencies as the human ear. NSNS mergers reach our sensitivity sweet spot for a few seconds; intermediate mass BHBH mergers get into the low end of our sweet spot. Supermassive black holes merge at very low frequencies outside of our sensitive band. LISA is a planned space-based observatory that would be sensitive in those bands: https://lisa.nasa.gov/ https://lisa.nasa.gov/
- raattgift 9y agoYes, NNS and BNS collisions are very messy. NNS are also very likely to form a BH. > Will we reasonably ever hear a supermassive BH collision? Hopefully! They'll certianly be looked for. There are some extremely massive SMBHs out there (e.g. Blazar QSO B0218+357), and it's reasonable to think that at least some of them are the result of mergers of SMBHs rather than, say, a rain of smaller BHs (and dust, gas and stars) onto an already big BH (which may also happen). https://www.youtube.com/watch?v=vw2sLcyV7Vc https://www.youtube.com/watch?v=vw2sLcyV7Vc https://www.youtube.com/watch?v=ow9JCXy1QdY https://www.youtube.com/watch?v=ow9JCXy1QdY http://newscenter.lbl.gov/2017/08/02/new-space-simulations-neutron-star-black-hole-mergers/ http://newscenter.lbl.gov/2017/08/02/new-space-simulations-n...
- stefco_ 9y agoBut we won't detect them with LIGO. We will need a lower-frequency detector, like the space-based LISA design, to do that. It's just like how we have optical telescopes for visible light and radio telescopes for light at different frequencies. Different interferometer designs will pick up different phenomena based on what their sensitive band is.