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Simultaneous Multi-Wavelength Observations of Sgr A* during 2007 April 1-11 | F. Yusef-Zadeh
; H. Bushouse
; M. Wardle
; C. Heinke
; D. A. Roberts
; C.D. Dowell
; A. Brunthaler
; M. J. Reid
; C. L. Martin
; D. P. Marrone
; D. Porquet
; N. Grosso
; K. Dodds-Eden
; G. C. Bower
; H. Wiesemeyer
; A. Miyazaki
; S. Pal
; S. Gillessen
; A. Goldwurm
; G. Trap
; H. Maness
; | Date: |
22 Jul 2009 | Abstract: | We report the detection of variable emission from Sgr A* in almost all
wavelength bands (i.e. cm, mm, submm, near-IR and X-rays) during a
multi-wavelength observing campaign. Three new moderate flares are detected
simultaneously in both near-IR (NIR) and X-ray bands. The ratio of X-ray to NIR
flux in the flares is consistent with inverse Compton scattering of NIR photons
by submm emitting relativistic particles which follow scaling relations
obtained from size measurements of Sgr A*. We also find that the flare
statistics in NIR wavelengths is consistent with the probability of flare
emission being inversely proportional to the flux. At mm wavelengths, the
presence of flare emission at 43 GHz (7mm) using VLBA with milli-arcsecond
spatial resolution indicates the first direct evidence that hourly time scale
flares are localized within the inner 30x70 Schwarzschild radii of Sgr A*. We
also show several cross correlation plots between NIR, mm and submm light
curves that collectively demonstrate the presence of time delays between the
peaks of emission up to three hours. The evidence for time delays at mm and
submm wavelengths are consistent with the source of emission being optically
thick initially followed by a transition to an optically thin regime. In
particular, there is an intriguing correlation between the optically thin NIR
and X-ray flare and optically thick radio flare at 43 GHz that occurred on 2007
April 4. This would be the first evidence of a radio flare emission delayed
with respect to the NIR and X-ray flare emission. The time delay measurements
support the expansion of hot self-absorbed synchrotron plasma blob and weaken
the hot spot model of flare emission. | Source: | arXiv, 0907.3786 | Services: | Forum | Review | PDF | Favorites |
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