The protostar FU Orionis may not be bursting: dramatic accretion suppression in embedded young eccentric binaries
Abstract
In 1936, the protostar FU Orionis began to brighten. Two years later, it was 100 times brighter and has not dimmed since. This object defined the class of FUor-type accretion bursts in protostars. Previous attempts to model FUors simulate isolated protostellar discs, thereby limiting the mass available to drive the burst and shortening its duration. However, these protostars are embedded within the interstellar medium, from which they actively accrete via accretion streamers. This work seeks the origin of FUors starting at interstellar medium scales. An unbiased search of star particles from a 25AU resolution star cluster formation simulation was performed to find FUor candidates. Most candidates were low-mass secondary stars in highly eccentric binaries, like FU Orionis. Zoom-in simulations down to 0.79AU resolution found candidates experience dramatic accretion suppression and bursts at the closest binary separation at periastron. Approaching periastron, the candidate's orbital speed becomes supersonic striping away nearby gas. After periastron, the orbital speed decreases allowing gas to accrete onto the candidate rapidly via Bondi-Hoyle-Lyttleton (BHL) accretion. BHL accretion tails form behind the candidate and appear as accretion streamers. This dramatic suppression and burst near periastron is a physical mechanism for strong variable accretion in embedded young eccentric binaries. This mechanism also implies that FU Orionis returned to its former accretion rate.
Related
- Pulsed Accretion onto Eccentric Binaries in Highly Misaligned Circumbinary Disks
- Pulsed Accretion onto Eccentric Binaries in Highly Misaligned Circumbinary Disks
- Environmental Imprints of Dark Matter and Accretion Disks on Eccentric EMRIs around Kerr Black Holes
- Preferential accretion onto eccentric and unequal binary black holes
- Suppression of spiral density waves in collisionless accretion flows
BibTeX
@misc{kuruwita2026protostar,
title = {{The protostar FU Orionis may not be bursting: dramatic accretion suppression in embedded young eccentric binaries}},
author = {Rajika L. Kuruwita},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.23890},
eprint = {2609.23890},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.23890},
}
RIS
TY - UNPB
TI - The protostar FU Orionis may not be bursting: dramatic accretion suppression in embedded young eccentric binaries
AU - Rajika L. Kuruwita
PY - 2026
DA - 2026/09/20
PB - arXiv
DO - 10.48550/arxiv.2609.23890
UR - https://arxiv.org/abs/2609.23890
AB - In 1936, the protostar FU Orionis began to brighten. Two years later, it was 100 times brighter and has not dimmed since. This object defined the class of FUor-type accretion bursts in protostars. Previous attempts to model FUors simulate isolated protostellar discs, thereby limiting the mass available to drive the burst and shortening its duration. However, these protostars are embedded within the interstellar medium, from which they actively accrete via accretion streamers. This work seeks the origin of FUors starting at interstellar medium scales. An unbiased search of star particles from a 25AU resolution star cluster formation simulation was performed to find FUor candidates. Most candidates were low-mass secondary stars in highly eccentric binaries, like FU Orionis. Zoom-in simulations down to 0.79AU resolution found candidates experience dramatic accretion suppression and bursts at the closest binary separation at periastron. Approaching periastron, the candidate's orbital speed becomes supersonic striping away nearby gas. After periastron, the orbital speed decreases allowing gas to accrete onto the candidate rapidly via Bondi-Hoyle-Lyttleton (BHL) accretion. BHL accretion tails form behind the candidate and appear as accretion streamers. This dramatic suppression and burst near periastron is a physical mechanism for strong variable accretion in embedded young eccentric binaries. This mechanism also implies that FU Orionis returned to its former accretion rate.
ER -