Astronomy and Astrophysics – Astrophysics
Scientific paper
2007-12-18
Astronomy and Astrophysics
Astrophysics
28 pages, 9 figures, 2 tables, ApJ July 20, 2008
Scientific paper
10.1086/588803
Sgr A*, the massive black hole at the center of the Galaxy, varies in radio through X-ray emission on hourly time scales. The flare activity is thought to arise from the innermost region of an accretion flow onto Sgr A*. We present simultaneous light curves of Sgr A* in radio, sub-mm and X-rays that show a possible time delay of 110$\pm17$ minutes between X-ray and 850 $\mu$m suggesting that the sub-mm flare emission is optically thick. At radio wavelengths, we detect time lags of of $20.4\pm6.8, 30\pm12$ and 20$\pm6$ minutes between the flare peaks observed at 13 and 7 mm (22 and 43 GHz) in three different epochs using the VLA. Linear polarization of 1$\pm0.2$% and 0.7$\pm0.1$% is detected at 7 and 13 mm, respectively, when averaged over the entire observation on 2006 July 17. A simple model of a bubble of synchrotron emitting electrons cooling via adiabatic expansion can explain the time delay between various wavelengths, the asymmetric shape of the light curves, and the observed polarization of the flare emission at 43 and 22 GHz. The derived physical quantities that characterize the emission give an expansion speed of v$_{exp} \sim 0.003-0.1$c, magnetic field of B$\sim$10-70 Gauss and particle spectral index p$\sim$1-2. These parameters suggest that the associated plasma cannot escape from Sgr A* unless it has a large bulk motion.
Baganoff Frederick Keith
Cotton William D.
Dowell Charles (Darren)
Heinke Craig
Roberts Dale
No associations
LandOfFree
Simultaneous Chandra, CSO and VLA Observations of Sgr A*: The Nature of Flaring Activity does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Simultaneous Chandra, CSO and VLA Observations of Sgr A*: The Nature of Flaring Activity, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Simultaneous Chandra, CSO and VLA Observations of Sgr A*: The Nature of Flaring Activity will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-549040