Low-angular-momentum accretion shocks can power weak-to-moderate X-ray flares from SgrA*
Abstract
X-ray flares from Sgr~A* span broad ranges in duration, fluence, and luminosity, but their origin remains unsettled. We test whether standing shocks in low-angular-momentum magnetized accretion flows can provide a viable energy reservoir to account for these events. Using semi-analytic trans-magnetosonic shock solutions, we estimate the kinetic energy available in the downstream post-shock flow and compare it with the 25-year \textit{Chandra} X-ray flare catalog. For each theoretical solution, we compute the required efficiency ε=Edata/Esh, where Edata is the observed radiated energy for each flare and Esh is the available energy in the shocked flow. Notably, the weak flares require ε∼10−3--10−2, while moderate flares require a few percent. We perform the analyses for weakly and highly spinning cases, and the resulting weak-to-moderate flare energy budget remains unchanged. For the fiducial accretion rate and bolometric correction, the kinetic energy reservoir in standing shock is sufficient for the observed weak-to-moderate flare population, whereas the strongest events likely require higher efficiency which can be mediated via additional magnetic energy dissipation channel.
Related
- Magnetized Accretion Flows with Low Angular Momentum Around Supermassive Black Holes
- Three-dimensional simulations of accretion disks in pre-CE systems -- II. Accretion efficiency and angular momentum transport
- Angular Momentum Transport across Accretion States around a rapidly spinning black hole
- The impact of hot mode accretion and angular momentum conservation on metallicity gradients of galactic discs
- Fast Radio Bursts from Monster Shocks and Flares of Inspiraling Binary Neutron Stars: A Kinetic Model for Double Pulsar
BibTeX
@misc{mitra2026lowangularmomentum,
title = {{Low-angular-momentum accretion shocks can power weak-to-moderate X-ray flares from SgrA*}},
author = {Samik Mitra and Bożena Czerny and Michal Zajaček and Zach Sumners},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.04145},
eprint = {2609.04145},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.04145},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Low-angular-momentum accretion shocks can power weak-to-moderate X-ray flares from SgrA*
AU - Samik Mitra
AU - Bożena Czerny
AU - Michal Zajaček
AU - Zach Sumners
PY - 2026
DA - 2026/09/03
PB - arXiv
DO - 10.48550/arxiv.2609.04145
UR - https://arxiv.org/abs/2609.04145
AB - X-ray flares from Sgr~A* span broad ranges in duration, fluence, and luminosity, but their origin remains unsettled. We test whether standing shocks in low-angular-momentum magnetized accretion flows can provide a viable energy reservoir to account for these events. Using semi-analytic trans-magnetosonic shock solutions, we estimate the kinetic energy available in the downstream post-shock flow and compare it with the 25-year \textit{Chandra} X-ray flare catalog. For each theoretical solution, we compute the required efficiency ε=E_data/E_sh, where E_data is the observed radiated energy for each flare and E_sh is the available energy in the shocked flow. Notably, the weak flares require ε∼10^−3--10^−2, while moderate flares require a few percent. We perform the analyses for weakly and highly spinning cases, and the resulting weak-to-moderate flare energy budget remains unchanged. For the fiducial accretion rate and bolometric correction, the kinetic energy reservoir in standing shock is sufficient for the observed weak-to-moderate flare population, whereas the strongest events likely require higher efficiency which can be mediated via additional magnetic energy dissipation channel.
ER -