Jet flares as beacons for gravitational waves
László Árpád Gergely (1), Márton Tápai (2), Zoltán Keresztes (3)
1 : Departments of Theoretical and Experimental Physics, University of Szeged, Dóm tér 9, 6720 Szeged,
Hungary, email: laszlo.a.gergely@gmail.com
2 : Departments of Theoretical and Experimental Physics, University of Szeged, Dóm tér 9, 6720 Szeged,
Hungary, email: tapai@titan.physx.u-szeged.hu
3 : Departments of Theoretical and Experimental Physics, University of Szeged, Dóm tér 9, 6720 Szeged,
Hungary, email: zkeresztes@titan.physx.u-szeged.hu
Flares in a relativistic jet spectrum may suggest the precession of the spin in a supermassive black hole (SMBH)
binary lying at the jet base. Such a precession is dominated by the spin-orbit interaction and the flares appear as
a result of the jet sweeping over the line of sight.
Due to gravitational wave (GW) emission, the precession cone narrows and eventually the flares disappear. Such
a transient phenomenon is likely to happen when a spin-flip occurs during the inspiral. The condition for this is
that the mass ratio of the SMBHs falls into the range 1:3 to 1:30.
It is possible in principle to measure both
i) the precession timescale Tp and
ii) the time T while this transient phenomenon lasts (during which the precession cone narrows by a
certain angle  ).
Complementary GW emission from the SMBH binary could fall into the best sensitivity range of the LISA detector.
We argue that with the aid of the time intervals
iii) TSNR10 (elapsed until the signal to noise ratio of GWs overpasses a certain critical value, hence it is
detected) and
iv) Tmerger (further elapsed until the merger occurs, hence when the GW signal disappears)
it becomes possible to identify all astrophysical parameters of the SMBH binary.
With this we suggest a new and powerful method of combining observations on jets with GW observations
a) capable of determining the total mass, mass ratio, spin magnitude, sky position and distance of a
merging SMBH binary,
b) allowing the reconstruction of the inspiral history (the orbital evolution, precession characteristics and
evolution of the spin orientation with respect to the orbital plane).