test_moissonnage_selune
type: Agent

Concurrent X-ray, near-infrared, sub-millimeter, and GeV gamma-ray observations of Sagittarius A
type: Dataset
contact point: Organization
  fn: CCSD
keyword: radiation-mechanisms-non-thermal
keyword: infrared-general
keyword: submillimeter-general
keyword: galaxy-center
keyword: black-hole-physics
keyword: physastrhephysics-physicsastrophysics-astro-phhigh-energy-astrophysical-phenomena-astro-p
keyword: journal-articles
keyword: x-rays-general
keyword: infoeu-reposemanticsarticle
keyword: sduastrhesciences-of-the-universe-physicsastrophysics-astro-phhigh-energy-astrophysical-ph
landing page: 0004-6361
description: Aims: The radiative counterpart of the supermassive black hole at the Galactic center (GC), Sgr A⋆, is subject to frequent flares that are visible simultaneously in X-rays and the near-infrared (NIR). Often, enhanced radio variability from centimeter to sub-millimeter wavelengths is observed to follow these X-ray/NIR eruptions. We present here a multi-wavelength campaign carried out in April 2009, with the aim of characterizing this broadband flaring activity. Methods: Concurrent data from the XMM-Newton/EPIC (2-10 keV), VLT/NACO (2.1 μm, 3.8 μm), APEX/LABOCA (870 μm), and Fermi/LAT (0.1-200 GeV) instruments are employed to derive light curves and spectral energy distributions of new flares from Sgr A⋆. Results: We detected two relatively bright NIR flares, both associated with weak X-ray activity, one of which was followed by a strong sub-mm outburst ~200 min later. Photometric spectral information on a NIR flare was obtained for the first time with NACO, giving a power-law photon index α = -0.4 ± 0.3 (Fν ∝ ν α). The first attempt to detect flaring activity from the Fermi GC source 1FGL J1745.6-2900 is also reported. We model NIR, X-ray, and sub-mm flares in the context of non-thermal emission processes. We find that the simplest scenario involving a single expanding plasmoid releasing synchrotron NIR/sub-mm and synchrotron self-Compton X-ray radiation is inadequate to reproduce the data, but we offer suggestions to reconcile the basic elements of the theory and the observations.
issued: 2026-05-28T16:29:34.107220
language: en
modified: 2026-05-28T16:29:34.107226

Concurrent X-ray, near-infrared, sub-millimeter, and GeV gamma-ray observations of Sagittarius A
type: Distribution
access URL: https://in2p3.hal.science/in2p3-00670177
format: HTML
issued: 2026-05-28T16:29:34.133941
modified: 2026-05-28T16:29:34.068434