2006/03/31 by F. Yusef-Zadeh, F. Yusef‐Zadeh, D. A. Roberts +5 · 6 citations
Earth and Planetary Sciences · Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Star Formation Studies #High-pressure geophysics and materials #astro-ph
paper · pdf · doi:10.1086/506375
published as Astrophys.J.650:189-194,2006 · Revised with new Figures 1 and 2, 17 pages, 4 figures, ApJ (in press)
arxiv created 2006/05/24 · openalex publication_date 2006/10/10 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We have carried out Very Large Array (VLA) continuum observations to study the variability of Sgr A* at 43 GHz (λ = 7 mm) and 22 GHz (λ = 13 mm). A low level of flare activity has been detected with a duration of ~2 hr at these frequencies, showing the peak flare emission at 43 GHz leading the 22 GHz peak flare by ~20-40 minutes. The overall characteristics of the flare emission are interpreted in terms of the plasmon model of van der Laan by considering the ejection and adiabatic expansion of a uniform, spherical plasma blob due to flare activity. The observed peak of the flare emission with a spectral index, ν -α , of α = 1.6 is consistent with the prediction that the peak emission shifts toward lower frequencies in an adiabatically expanding self-absorbed source. We present the expected synchrotron light curves for an expanding blob, as well as the peak frequency emission, as a function of the energy spectral index constrained by the available flaring measurements in near-IR, submillimeter, millimeter, and radio wavelengths. We note that the blob model is consistent with the available measurements; however, we cannot rule out the jet of Sgr A*. If expanding material leaves the gravitational potential of Sgr A*, the total mass-loss rate of nonthermal and thermal particles is estimated to be ≤2 × 10 -8 M ☉ yr -1 . We discuss the implication of the mass-loss rate, since this value matches closely the estimated accretion rate based on polarization measurements.