Kavli Affiliate: Xian Chen
| First 5 Authors: Yang Yang, Jie Yang, Xian Chen, Zihan Zhang,
| Summary:
Extreme mass ratio inspiral (EMRI) systems composed of low-mass white dwarfs
(WDs, $0.1 – 0.3$ $mathrm{M}_{odot } $) and intermediate-mass black holes
(IMBHs, $10^{3} – 10^{5}$ $mathrm{M}_{odot } $) are ideal objects for
multi-messenger astronomy because they produce both gravitational wave (GW) and
electromagnetic (EM) signals. Both relativistic effects and the mass transfer
(MT) process are important for determining orbital dynamics, but the current
model has not taken these ingredients fully into account. Here we use a
perturbed Keplerian framework and the post-Newtonian (PN) formalism to model
the relativistic orbit of a WD around a spinning IMBH. We pay special attention
to the dynamical evolution during a narrow phase near the orbital pericenter
where the WD fills the Roche lobe and starts MT. We find that gravitational
radiation and MT have opposing effects on orbital evolution. When MT
predominates, the orbital period and eccentricity could may increase, sometimes
enabling the WD to escape and avoid tidal disruption. Additionally, we estimate
the time required for the GW phase to shift by one radian due to the MT process
and identify cases where this phase shift will be detectable by future GW
observations. The temporal expansion of the orbit during MT offers a potential
explanation for the disappearance of quasi-periodic eruptions (QPEs) found in
several X-ray transients, highlighting the importance of including both the
relativistic and MT processes in the WD-IMBH model.
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