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Monitoring the Galactic Centre with Australia Telescope Compact Array | | A. Borkar
; A. Eckart
; C. Straubmeier
; D. Kunneriath
; B. Jalali
; N. Sabha
; B. Shahzamanian
; M. García-Marín
; M. Valencia-S
; L. Sjouwerman
; S. Britzen
; V. Karas
; M. Dovčiak
; A. Donea
; A. Zensus
; | | Date: |
2 May 2016 | | Abstract: | The supermassive black hole, Sagittarius A* (Sgr A*), at the centre of the
Milky Way undergoes regular flaring activity which is thought to arise from the
innermost region of the accretion flow. We performed the monitoring
observations of the Galactic Centre to study the flux-density variations at 3mm
using the Australia Telescope Compact Array (ATCA) between 2010 and 2014. We
obtain the light curves of Sgr A* by subtracting the contributions from the
extended emission around it, and the elevation and time dependent gains of the
telescope. We perform structure function analysis and the Bayesian blocks
representation to detect flare events. The observations detect six instances of
significant variability in the flux density of Sgr A* in three observations,
with variations between 0.5 to 1.0 Jy, which last for 1.5 $-$ 3 hours. We use
the adiabatically expanding plasmon model to explain the short time-scale
variations in the flux density. We derive the physical quantities of the
modelled flare emission, such as the source expansion speed $v_{mathrm{exp}}$,
source sizes, spectral indices, and the turnover frequency. These parameters
imply that the expanding source components are either confined to the immediate
vicinity of Sgr A* by contributing to the corona or the disc, or have a bulk
motion greater than $v_{mathrm{exp}}$. No exceptional flux density variation
on short flare time-scales was observed during the approach and the flyby of
the dusty S-cluster object (DSO/G2). This is consistent with its compactness
and the absence of a large bow shock. | | Source: | arXiv, 1605.0424 | | Services: | Forum | Review | PDF | Favorites | |
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