Isolated NS discussion notes ---------------------------- 1) Nils & Kostas: Mano-a-mano challenge: how to get a kick large enough to excite detectable GWs In current EOS models of NS cores, their parameters do not necessarily cover all possibilities (can be re-adjusted to take into account of new observations, eg. max mass) EOS must include all physics Theory models cannot explain observed magnetic fields unsure how angular momentum is imparted during glitch (require ~1%), crust does not quite have enough (new calculations) and core has ~90% of angular momention which is too much temperature cooling profile suggests that many LMXBs should be radiating GWs through r-mode instabilities (CFS) but that is definitely not the case. So, there has to be a different explanation, revert to old model for dissipation limiting rotation frequency f-mode instability will not grow to a high amplitude? saturation amplitude is not fixed should be ~1e-3 to 1e-5 Alfven wave oscillations (due to B field) shown to be possible explanation of QPOs observed in SGR hyperflares numerical models do not show "nice"/stable toroidal and dipole magnetic fields which were used in perturbative calculations, instead interior B field in NS is dynamic. So, do not have enough understanding on what is happening within NS though there will eventually be a stable structure but at a time scale longer than the simulations (>400 ms), could be a year need B field ~ 8e16 G (very high) for detectable signal by ET how likely are these modes excited within 20Mpc? Unlikely because many of the NS within range are rotating very slowly, one requires large field and fast rotation which can happen after supernova estimates for fast rotating stars are at a rate of 1 per 1e3 to 1e4, yes but if the fast rotation occurs only for a very short phase just after birth, then we won't see this fast rotation but will still be fast rotating but only for a very short time are f-modes stronger emitter than supernova itself? Only if you can turn on these instabilities with fast rotation what about magnetars being formed from merger of neutron stars? It's complicated and the mechanism for creating the magnetar is uncertain, hard to have strong magnetic fields that are coherent and live on 2) James: GWs from f-modes Even with ET, only probe upper limit of energy estimated from theory. Cannot constrain (any?) plausible models Steiner plot shows that radius does not vary much with mass over plausible NS range does the mode structure allow searches to reject glitches? It helps with parameter estimation definitely but not sure about effect on searches f-mode efficient radiator, which mode (r/f) depends on astrophysics of excitation f-mode parameters no effected much by B field, etc 3) Ignacio: transient GWs from r-modes It is possible that the sheer viscosity factor (delta u/u) should not change as a function of rotation frequency and, instead, remain 1 all the time. So the stronger signals at higher frequencies will look less attractive since that signals will be 10 times shorter than in the Levin-Ushomirsky model. Also, it is unclear that the energies observed in the EM a strongly related to the energy of GWs emitted as a result. There should be some modelling of for these sources but it is complicated. Ultimately, the EM energies should be an upper limit.