scholarly journals General Relativistic Flux Modulations in the Galactic Center Black Hole Candidate Sagittarius A*

1995 ◽  
Vol 448 (1) ◽  
Author(s):  
J. M. Hollywood, ◽  
Fulvio Melia, ◽  
Laird M. Close, ◽  
Donald W. McCarthy, Jr., ◽  
Tatia A. DeKeyser
Keyword(s):  
Black Hole ◽  
Galactic Center ◽  
Black Hole Candidate ◽  
Sagittarius A ◽  
General Relativistic

scholarly journals Detection of Circular Polarization in the Galactic Center Black Hole Candidate Sagittarius A*

1999 ◽  
Vol 523 (1) ◽  
pp. L29-L32 ◽  
Author(s):  
Geoffrey C. Bower ◽  
Heino Falcke ◽  
Donald C. Backer
Keyword(s):  
Black Hole ◽  
Circular Polarization ◽  
Galactic Center ◽  
Black Hole Candidate ◽  
Sagittarius A

scholarly journals Observing a black hole event horizon: (sub)millimeter VLBI of Sgr A*

2009 ◽  
Vol 5 (S261) ◽  
pp. 271-276 ◽  
Author(s):  
Vincent L. Fish ◽  
Sheperd S. Doeleman
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Strong Evidence ◽  
Galactic Center ◽  
Strong Field ◽  
Variable Component ◽  
Massive Black Hole ◽  
Black Hole Candidate ◽  
Long Baseline ◽  
Sgr A

AbstractVery strong evidence suggests that Sagittarius A*, a compact radio source at the center of the Milky Way, marks the position of a super massive black hole. The proximity of Sgr A* in combination with its mass makes its apparent event horizon the largest of any black hole candidate in the universe and presents us with a unique opportunity to observe strong-field GR effects. Recent millimeter very long baseline interferometric observations of Sgr A* have demonstrated the existence of structures on scales comparable to the Schwarzschild radius. These observations already provide strong evidence in support of the existence of an event horizon. (Sub)Millimeter VLBI observations in the near future will combine the angular resolution necessary to identify the overall morphology of quiescent emission, such as an accretion disk or outflow, with a fine enough time resolution to detect possible periodicity in the variable component of emission. In the next few years, it may be possible to identify the spin of the black hole in Sgr A*, either by detecting the periodic signature of hot spots at the innermost stable circular orbit or parameter estimation in models of the quiescent emission. Longer term, a (sub)millimeter VLBI “Event Horizon Telescope” will be able to produce images of the Galactic center emission to the see the silhouette predicted by general relativistic lensing. These techniques are also applicable to the black hole in M87, where black hole spin may be key to understanding the jet-launching region.

scholarly journals The reflection of two past outbursts of Sagittarius A* observed by Chandra during the last decade

2013 ◽  
Vol 9 (S303) ◽  
pp. 344-348
Author(s):  
M. Clavel ◽  
R. Terrier ◽  
A. Goldwurm ◽  
M. R. Morris ◽  
G. Ponti ◽  
...  
Keyword(s):  
Black Hole ◽  
Galactic Center ◽  
Line Of Sight ◽  
High Resolution Data ◽  
The Past ◽  
Sagittarius A ◽  
Cloud Parameters ◽  
Angular Scale ◽  
Sgr A ◽  
First Time

AbstractThe supermassive black hole at the Galactic center, Sagittarius A* has experienced periods of higher activity in the past. The reflection of these past outbursts is observed in the molecular material surrounding the black hole but reconstructing its precise lightcurve is difficult since the distribution of the clouds along the line of sight is poorly constrained.Using Chandra high-resolution data collected from 1999 to 2011 we studied both the 6.4 keV and the 4–8 keV emission of the region located between Sgr A* and the Radio arc, characterizing its variations down to 15″ angular scale and 1-year time scale. The emission from the molecular clouds in the region varies significantly, showing either a 2-year peaked emission or 10-year linear variations. This is the first time that such fast variations are measured. Based on the cloud parameters, we conclude that these two behaviors are likely due to two distinct past outbursts of Sgr A* during which its luminosity rose to at least 1039 erg s−1.

scholarly journals Search for time lag in intra-day variability of Sgr A*

2013 ◽  
Vol 9 (S303) ◽  
pp. 322-323
Author(s):  
A. Miyazaki ◽  
S. S. Lee ◽  
B. W. Sohn ◽  
T. Jung ◽  
M. Tsuboi ◽  
...  
Keyword(s):  
Black Hole ◽  
Galactic Center ◽  
Time Lag ◽  
Light Curves ◽  
Time Lags ◽  
Significant Time ◽  
Sagittarius A ◽  
Receiver System ◽  
Sgr A ◽  
Plasma Blobs

AbstractWe searched the time lag between the intra-day variables (IDVs) of Sagittarius A* at 22, 43, and 86 GHz bands using the Korean VLBI Network (KVN). The time lags between the IDV flare peaks at 22 and 43 GHz are reported, and they suggest that the flare emissions come from adiabatically expanding plasma blobs, ejected close to the Galactic center black hole. We searched the time lags between light curves at 90 and 102 GHz using the Nobeyama Millimeter Array, but could not find significant time lags. In order to detect the diversity of the time lags of Sgr A* flares, we performed observations of Sgr A* in the 22, 43, and 86 GHz bands using the KVN in the winter of 2013. Because the receiver system of KVN can observe Sgr A* in these three bands simultaneously, the KVN is very useful to detect the time lags of Sgr A* flares.

scholarly journals Bright X-Ray Stars near the Galactic Center

1998 ◽  
Vol 188 ◽  
pp. 366-367 ◽  
Author(s):  
Masaaki Sakano ◽  
Mamiko Nishiuchi ◽  
Yoshitomo Maeda ◽  
Katsuji Koyama ◽  
Jun Yokogawa
Keyword(s):  
Black Hole ◽  
Galactic Center ◽  
Emission Mechanism ◽  
Paper Report ◽  
X Ray ◽  
Black Hole Candidate

This paper report the ASCA observations of the three brightest persistent X-ray stars near the Galactic Center: an X-ray burster A1742-294, black hole candidate 1E 1740.7-2942, and unclassified source 1E 1743.1-2843. Emission mechanism is briefly discussed based on the new ASCA results.

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