Improved analysis of time delays between radio wavelengths and X-ray of Sgr A* flares in the shock oscillation model
- 1Institute of Astronomy and Astrophysics, Academia Sinica , Taipei 10617, Taiwan ,
- 2Hakodate Campus, Hokkaido University of Education , Hachiman-Cho 1-2, Hakodate 040-8567 ,
- 3Calle 134A No. 148A 21 San Pedro de Tibabuyes , Suba - Bogotá ,
Abstract
We present an improved analysis of the time delays between radio and X-ray flares from the supermassive black hole Sagittarius A*, extending our previous shock oscillation model by incorporating Compton scattering. Our simulations predict the following delay times: 1–4 h between X-ray and radio flares, 20–40 min and 0.5–1 h between 334 GHz and 4.5 μm and 2–8 keV flares, and 7–20 min and 0.5–1 h between 22–43 and 350 GHz radio flares. These findings are in good agreement with recent observations. The delay time between the radio emissions (synchrotron) and X-ray emissions (bremsstrahlung) is interpreted as the transit time for sound waves travelling from the central core near the event horizon to the location of the oscillating shock. Additionally, the delay time observed between different radio wavelengths corresponds to the transit time of sound waves moving between the frequency-dependent effective radii Reff(ν), where the optical thickness τ ν (R) at frequency ν equals one on the surface of the accretion disc. The X-ray emission and the radio emission at lower frequencies peak later than the radio emission at higher frequencies. This delay occurs because the acoustic perturbations created by synchrotron emission peak near the event horizon and then expand outward. Conversely, an inverse delay happens when the acoustic waves generated by the upstream shock wave travel towards the event horizon. The predicted delay times from this interpretation qualitatively match the numerical results obtained in simulations.
Related
- An Evolving Leptonic Jet Model for Delayed Radio Flares in Neutrino Blazars
- The Association of Solar Radio Bursts with Eruptive and Confined Flares
- Type I Solar Radio Bursts Modulated by Solar Flares
- Fast Radio Bursts from Monster Shocks and Flares of Inspiraling Binary Neutron Stars: A Kinetic Model for Double Pulsar
- Type III radio bursts associated with jets in two solar flares
BibTeX
@article{aktar2026improved,
title = {{Improved analysis of time delays between radio wavelengths and X-ray of Sgr A* flares in the shock oscillation model}},
author = {Ramiz Aktar and Toru Okuda and Chandra B Singh},
journal = {Monthly Notices of the Royal Astronomical Society},
year = {2026},
month = oct,
doi = {10.1093/mnras/stag1925},
url = {https://academic.oup.com/mnras/article/doi/10.1093/mnras/stag1925/8907353},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Improved analysis of time delays between radio wavelengths and X-ray of Sgr A* flares in the shock oscillation model
AU - Ramiz Aktar
AU - Toru Okuda
AU - Chandra B Singh
PY - 2026
DA - 2026/10/10
JO - Monthly Notices of the Royal Astronomical Society
DO - 10.1093/mnras/stag1925
UR - https://academic.oup.com/mnras/article/doi/10.1093/mnras/stag1925/8907353
AB - We present an improved analysis of the time delays between radio and X-ray flares from the supermassive black hole Sagittarius A*, extending our previous shock oscillation model by incorporating Compton scattering. Our simulations predict the following delay times: 1–4 h between X-ray and radio flares, 20–40 min and 0.5–1 h between 334 GHz and 4.5 μm and 2–8 keV flares, and 7–20 min and 0.5–1 h between 22–43 and 350 GHz radio flares. These findings are in good agreement with recent observations. The delay time between the radio emissions (synchrotron) and X-ray emissions (bremsstrahlung) is interpreted as the transit time for sound waves travelling from the central core near the event horizon to the location of the oscillating shock. Additionally, the delay time observed between different radio wavelengths corresponds to the transit time of sound waves moving between the frequency-dependent effective radii R_eff(ν), where the optical thickness τ _ν (R) at frequency ν equals one on the surface of the accretion disc. The X-ray emission and the radio emission at lower frequencies peak later than the radio emission at higher frequencies. This delay occurs because the acoustic perturbations created by synchrotron emission peak near the event horizon and then expand outward. Conversely, an inverse delay happens when the acoustic waves generated by the upstream shock wave travel towards the event horizon. The predicted delay times from this interpretation qualitatively match the numerical results obtained in simulations.
SN - 0035-8711
SN - 1365-2966
ER -