Low-angular-momentum Accretion Shocks Can Power Weak-to-moderate X-Ray Flares from Sgr A*
5 affiliations
- 1Tata Institute of Fundamental Research
- 2Center for Theoretical Physics
- 3Masaryk University
- 4McGill University
- 53550 Rue University
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 semianalytic trans-magnetosonic shock solutions, we estimate the kinetic energy available in the downstream postshock flow and compare it with the 25 yr 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 an additional magnetic energy dissipation channel.
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BibTeX
@article{mitra2026lowangularmomentum,
title = {{Low-angular-momentum Accretion Shocks Can Power Weak-to-moderate X-Ray Flares from Sgr A*}},
author = {Samik Mitra and Bożena Czerny and Michal Zajaček and Zach Sumners},
journal = {The Astrophysical Journal},
year = {2026},
month = oct,
doi = {10.3847/1538-4357/aea3f2},
url = {https://iopscience.iop.org/article/10.3847/1538-4357/aea3f2},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Low-angular-momentum Accretion Shocks Can Power Weak-to-moderate X-Ray Flares from Sgr A*
AU - Samik Mitra
AU - Bożena Czerny
AU - Michal Zajaček
AU - Zach Sumners
PY - 2026
DA - 2026/10/16
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/aea3f2
UR - https://iopscience.iop.org/article/10.3847/1538-4357/aea3f2
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 semianalytic trans-magnetosonic shock solutions, we estimate the kinetic energy available in the downstream postshock flow and compare it with the 25 yr 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 an additional magnetic energy dissipation channel.
SN - 0004-637X
SN - 1538-4357
ER -