Kavli Affiliate: Pau Amaro Seoane
| First 5 Authors: Pau Amaro Seoane, Yiren Lin, Kostas Tzanavaris, ,
| Summary:
The gravitational capture of a stellar-mass object by a supermassive black
hole represents a unique probe of warped spacetime. The small object, typically
a stellar-mass black hole, describes a very large number of cycles before
crossing the event horizon. Because of the mass difference, we call these
captures extreme-mass ratio inspirals (EMRIs). Their merger event rate at the
Galactic Centre is negligible, but the amount of time spent in the early
inspiral is not. Early EMRIs (E-EMRIs) spend hundreds of thousands of years in
band during this phase. At very early stages, the peak of the frequency will
not change during an observational time. At later stages, it will change a bit
and finally the EMRI explores a wide range of them when it is close to merger.
We distinguish between “monocromatic” E-EMRIs, which do not change their
(peak) frequency, oligochromatic E-EMRIs, which explore a short range and
polychromatic ones, the EMRIs which have been discussed so far in the
literature. We derive the number of E-EMRIs at the Galactic Centre, and their
signal-to-noise ratios (SNR) and perform a study of parameter extraction. We
show that parameters such as the spin and the mass can be extracted with an
error which can be as small as $10^{-11}$ and $10^{-5},M_{odot}$. There are
between hundreds and thousands of E-EMRIs in their monochromatic stage at the
GC, and tens in their oligochromatic phase. The SNR ranges from a minimum of
$10$ (larger likelihood) to a maximum of $10^6$ (smaller likelihood). Moreover,
we derive the contribution signal corresponding to the incoherent sum of
continuous with two representatives masses; $10,M_{odot}$ and $40,M_{odot}$
and show that their curves will cover a significant part of LISA’s sensitivity
curve. Depending on their level of circularisation, they might be detected as
individual sources or form a foreground population.
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