Flaring Activity of Sgr A* at 43 and 22 GHz: Evidence for Expanding Hot Plasma
| dc.creator | Yusef-Zadeh, F. | |
| dc.creator | Roberts, D. | |
| dc.creator | Wardle, M. | |
| dc.creator | Heinke, C. O. | |
| dc.creator | Bower, G. C. | |
| dc.date | 2006-03-24 | |
| dc.date | 2006-05-24 | |
| dc.date.accessioned | 2026-07-07T10:43:43Z | |
| dc.date.available | 2026-07-07T10:43:43Z | |
| dc.description | We have carried out Very Large Array (VLA) continuum observations to study the variability of Sgr A* at 43 GHz ($λ$=7mm) and 22 GHz ($λ$=13mm). A low level of flare activity has been detected with a duration of $\sim$ 2 hours at these frequencies, showing the peak flare emission at 43 GHz leading the 22 GHz peak flare by $\sim20$ to 40 minutes. The overall characteristics of the flare emission are interpreted in terms of the plasmon model of Van der Laan (1966) by considering the ejection and adiabatically 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, sub-millimeter, millimeter and radio wavelengths. We note that the blob model is consistent with the available measurements, however, we can not 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 $\le 2\times10^{-8}$ M$_\odot$ yr$^{-1}$. We discuss the implication of the mass-loss rate since this value matches closely with the estimated accretion rate based on polarization measurements. | |
| dc.description | Revised with new Figures 1 and 2, 17 pages, 4 figures, ApJ (in press) | |
| dc.identifier | https://arxiv.org/abs/astro-ph/0603685 | |
| dc.identifier | http://arxiv.org/abs/astro-ph/0603685 | |
| dc.identifier | Astrophys.J.650:189-194,2006 | |
| dc.identifier | doi:10.1086/506375 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/182344 | |
| dc.subject | Astrophysics | |
| dc.title | Flaring Activity of Sgr A* at 43 and 22 GHz: Evidence for Expanding Hot Plasma | |
| dc.type | text |