Year: 2026
Type: article
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.
Source: The Astrophysical Journal
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
OpenAlex ID: W7221866336