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Abstract Many studies have recently documented the orbital response of eccentric binaries accreting from thin circumbinary disks, characterizing the change in the binary semimajor axis and eccentricity. We extend these calculations to include the precession of the binary’s longitude of periapse induced by the circumbinary disk, and we characterize this precession continuously with binary eccentricityebfor equal mass components. This disk-induced apsidal precession is prograde with a weak dependence on the binary eccentricity wheneb≲ 0.4 and decreases approximately linearly foreb≳ 0.4; yet at allebbinary precession is faster than the rates of change to the semimajor axis and eccentricity by an order of magnitude. We estimate that such precession effects are likely most important for subparsec separated binaries with masses ≲107M⊙, like LISA precursors. We find that accreting, equal-mass LISA binaries withM< 106M⊙(and the most massiveM∼ 107M⊙binaries out toz∼ 3) may acquire a detectable phase offset due to the disk-induced precession. Moreover, disk-induced precession can compete with general relativistic precession in a vacuum, making it important for observer-dependent electromagnetic searches for accreting massive binaries—like Doppler boost and binary self-lensing models—after potentially only a few orbital periods.
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Fast Methods for Computing Photometric Variability of Eccentric Binaries: Boosting, Lensing, and Variable Accretion
Abstract We analyze accretion-rate time series for equal-mass binaries in coplanar gaseous disks spanning a continuous range of orbital eccentricities up to 0.8 for both prograde and retrograde systems. The dominant variability timescales match those of previous investigations; the binary orbital period is dominant for prograde binaries withe≳ 0.1, with a 5 × longer “lump” period taking over fore≲ 0.1. This lump period fades and drops from 5 × to 4.5 × the binary period aseapproaches 0.1, where it vanishes. For retrograde orbits, the binary orbital period dominates ate≲ 0.55 and is accompanied by a 2 × longer timescale periodicity at higher eccentricities. The shape of the accretion-rate time series varies with binary eccentricity. For prograde systems, the orientation of an eccentric disk causes periodic trading of accretion between the binary components in a ratio that we report as a function of binary eccentricity. We present a publicly available tool,binlite, that can rapidly (≲0.01 s) generate templates for the accretion-rate time series onto either binary component for choice of binary eccentricity below 0.8. As an example use case, we build lightcurve models where the accretion rate through the circumbinary disk and onto each binary component sets contributions to the emitted specific flux. We combine these rest-frame, accretion-variability lightcurves with observer-dependent Doppler boosting and binary self-lensing. This allows a flexible approach to generating lightcurves over a wide range of binary and observer parameter space. We envisionbinliteas the access point to a living database that will be updated with state-of-the-art hydrodynamical calculations as they advance.
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- Award ID(s):
- 2206299
- PAR ID:
- 10561292
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 977
- Issue:
- 2
- ISSN:
- 0004-637X
- Format(s):
- Medium: X Size: Article No. 244
- Size(s):
- Article No. 244
- Sponsoring Org:
- National Science Foundation
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