scholarly journals Observing AGN sources with the Event Horizon Telescope

2019 ◽  
Vol 15 (S356) ◽  
pp. 257-257
Author(s):  
Maciek Wielgus
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Angular Resolution ◽  
Galactic Center ◽  
Data Set ◽  
Supermassive Black Hole ◽  
History Of ◽  
Schwarzschild Radius ◽  
Centaurus A

AbstractIn April 2017 Event Horizon Telescope (EHT) has delivered first resolved images of a shadow of a supermassive black hole. Apart from black hole sources in M87 and in the Galactic Center, observed with resolution comparable to the Schwarzschild radius scale, EHT observed multiple AGN sources during the 2017 campaign. These include 3C279, Centaurus A, OJ287 and more. For most of the considered sources EHT 2017 data set should allow to reconstruct images with highest angular resolution in the history of their observations, approaching 20 uas. While the analysis of these data is still ongoing, I will talk about the scientific opportunities related to observing AGN sources with the extreme resolution of the EHT as well as about the astrophysical questions that these observations may help answering.

scholarly journals The Shortest-Known–Period Star Orbiting Our Galaxy’s Supermassive Black Hole

Science ◽  
2012 ◽  
Vol 338 (6103) ◽  
pp. 84-87 ◽  
Author(s):  
L. Meyer ◽  
A. M. Ghez ◽  
R. Schödel ◽  
S. Yelda ◽  
A. Boehle ◽  
...  
Keyword(s):  
General Relativity ◽  
Black Hole ◽  
Gravitational Potential ◽  
Angular Resolution ◽  
Galactic Center ◽  
Data Set ◽  
Supermassive Black Hole ◽  
The Past ◽  
Orbital Periods

Stars with short orbital periods at the center of our Galaxy offer a powerful probe of a supermassive black hole. Over the past 17 years, the W. M. Keck Observatory has been used to image the galactic center at the highest angular resolution possible today. By adding to this data set and advancing methodologies, we have detected S0-102, a star orbiting our Galaxy’s supermassive black hole with a period of just 11.5 years. S0-102 doubles the number of known stars with full phase coverage and periods of less than 20 years. It thereby provides the opportunity, with future measurements, to resolve degeneracies in the parameters describing the central gravitational potential and to test Einstein’s theory of general relativity in an unexplored regime.

scholarly journals Deconvolving the Nucleus of Centaurus A Using Chandra PSF Library

2001 ◽  
Vol 205 ◽  
pp. 66-69
Author(s):  
Margarita Karovska ◽  
T. Aldcroft ◽  
M.S. Elvis ◽  
I.N. Evans ◽  
G. Fabbiano ◽  
...  
Keyword(s):  
Black Hole ◽  
Angular Resolution ◽  
High Angular Resolution ◽  
Central Source ◽  
X Ray ◽  
Preliminary Results ◽  
Multi Scale ◽  
Supermassive Black Hole ◽  
Scale Structures ◽  
Centaurus A

We describe preliminary results from our study of multi-scale structures in Centaurus A (NGC 5128) obtained using the Chandra X-ray Observatory HRC-I observations. The high-angular resolution Chandra images reveal X-ray multi-scale structures in this object with unprecedented detail and clarity. The region surrounding the Cen A nucleus, believed to be associated with a supermassive black hole, shows structures on arcsecond scales clearly resolved from the central source.

scholarly journals 15 years of high precision astrometry in the Galactic Center

2007 ◽  
Vol 3 (S248) ◽  
pp. 466-469
Author(s):  
S. Gillessen ◽  
R. Genzel ◽  
F. Eisenhauer ◽  
T. Ott ◽  
S. Trippe ◽  
...  
Keyword(s):  
Black Hole ◽  
Mass Distribution ◽  
Near Infrared ◽  
Galactic Center ◽  
Massive Black Hole ◽  
Data Set ◽  
Stellar Orbits ◽  
Supermassive Black Hole ◽  
Near Future ◽  
Precision Astrometry

AbstractIn 1992, we obtained the first observations of S2 a star close to the supermassive black hole at the Galactic Center. In 2002, S2 passed its periastron and in 2007, it completed a first fully observed revolution. This orbit allowed us to determine the mass of and the distance to the supermassive black hole with unprecedented accuracy. Here we present a re-analysis of the data set, enhancing the astrometric accuracy to 0.5 mas and increasing the number of well-determined stellar orbits to roughly 15. This allows to constrain the extended mass distribution around the massive black hole and will lead in the near future to the detection of post-Newtonian effects. We will also give an outlook on the potential of interferometric near-infrared astrometry with 10 microarcsecond accuracy from the VLTI.

scholarly journals Null Geodesics and Strong Field Gravitational Lensing in a String Cloud Background

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
M. Sharif ◽  
Sehrish Iftikhar
Keyword(s):  
Black Hole ◽  
Gravitational Lensing ◽  
Galactic Center ◽  
Deflection Angle ◽  
Orbital Motion ◽  
Strong Field ◽  
Schwarzschild Black Hole ◽  
Field Limit ◽  
Null Geodesics ◽  
Supermassive Black Hole

This paper is devoted to studying two interesting issues of a black hole with string cloud background. Firstly, we investigate null geodesics and find unstable orbital motion of particles. Secondly, we calculate deflection angle in strong field limit. We then find positions, magnifications, and observables of relativistic images for supermassive black hole at the galactic center. We conclude that string parameter highly affects the lensing process and results turn out to be quite different from the Schwarzschild black hole.

scholarly journals The Post-periapsis Evolution of Galactic Center Source G1: The Second Case of a Resolved Tidal Interaction with a Supermassive Black Hole

2017 ◽  
Vol 847 (1) ◽  
pp. 80 ◽  
Author(s):  
G. Witzel ◽  
B. N. Sitarski ◽  
A. M. Ghez ◽  
M. R. Morris ◽  
A. Hees ◽  
...  
Keyword(s):  
Black Hole ◽  
Galactic Center ◽  
Tidal Interaction ◽  
Supermassive Black Hole

scholarly journals A Deep Chandra View of a Candidate Parsec-scale Jet from the Galactic Center Supermassive Black Hole

2019 ◽  
Vol 875 (1) ◽  
pp. 44 ◽  
Author(s):  
Zhenlin Zhu ◽  
Zhiyuan Li ◽  
Mark R. Morris ◽  
Shuo Zhang ◽  
Siming Liu
Keyword(s):  
Black Hole ◽  
Galactic Center ◽  
Supermassive Black Hole

scholarly journals Universal interferometric signatures of a black hole’s photon ring

2020 ◽  
Vol 6 (12) ◽  
pp. eaaz1310 ◽  
Author(s):  
Michael D. Johnson ◽  
Alexandru Lupsasca ◽  
Andrew Strominger ◽  
George N. Wong ◽  
Shahar Hadar ◽  
...  
Keyword(s):  
General Relativity ◽  
Black Hole ◽  
Event Horizon ◽  
Infinite Sequence ◽  
High Order ◽  
Black Hole Mass ◽  
Tests Of General Relativity ◽  
Supermassive Black Hole ◽  
The Galaxy ◽  
Self Similar

The Event Horizon Telescope image of the supermassive black hole in the galaxy M87 is dominated by a bright, unresolved ring. General relativity predicts that embedded within this image lies a thin “photon ring,” which is composed of an infinite sequence of self-similar subrings that are indexed by the number of photon orbits around the black hole. The subrings approach the edge of the black hole “shadow,” becoming exponentially narrower but weaker with increasing orbit number, with seemingly negligible contributions from high-order subrings. Here, we show that these subrings produce strong and universal signatures on long interferometric baselines. These signatures offer the possibility of precise measurements of black hole mass and spin, as well as tests of general relativity, using only a sparse interferometric array.

scholarly journals The Nucleus of Our Home Galaxy: A Remnant of an Active or a Starburst Galaxy?

1994 ◽  
Vol 159 ◽  
pp. 351-354
Author(s):  
Leonid M. Ozernoy
Keyword(s):  
Black Hole ◽  
Galactic Center ◽  
Radiation Spectrum ◽  
Seyfert Galaxy ◽  
Star Formation History ◽  
Starburst Galaxy ◽  
Formation History ◽  
History Of ◽  
Sgr A ◽  
Radio Band

To resolve the above dilemma, two essentially different approaches are undertaken: First, a new, detailed analysis of the entire radiation spectrum of Sgr A∗, from radio band up to gamma-rays, is reviewed, which enables us to put substantial constraints on the mass of a putative black hole. The derived upper limit turns out to be too small to allow the black hole to serve as an ‘engine’ for a Seyfert galaxy. Second, analyses of recent data on the 10 KeV gas in the central 200 pc and on star formation history at the Galactic center both make a star burst the likely episode in a recent past. Taken together, the two approaches seem to indicate that the history of the central part of our Galaxy can be better described as that of a starburst, rather than a Seyfert, galaxy.

scholarly journals X-ray polarimetry – A new Window on Black Hole Systems

2016 ◽  
Vol 12 (S324) ◽  
pp. 338-341
Author(s):  
René W. Goosmann
Keyword(s):  
Black Hole ◽  
Binary Systems ◽  
Galactic Center ◽  
Galactic Nuclei ◽  
High Energy ◽  
X Ray ◽  
X Ray Imaging ◽  
History Of ◽  
Imaging Polarimetry ◽  
High Energy Emission

AbstractThree dedicated X-ray polarimetry mission projects are currently under phase A study at NASA and ESA. The need for this new observational window is more apparent than ever. On behalf of the consortium behind the X-ray Imaging Polarimetry Explorer (XIPE) we present here some prospects of X-ray polarimetry for our understanding of supermassive and stellar mass black hole systems. X-ray polarimetry is going to discriminate between leptonic and hadronic jet models in radio-loud active galactic nuclei. For leptonic jets it also puts important constraints on the origin of the seed photons that constitute the high energy emission via Comptonization. Another important application of X-ray polarimetry allows us to clarify the accretion history of the supermassive black hole at the Galactic Center. In a few Black Hole X-ray binary systems, X-ray polarimetry allows us to estimate in a new, independent way the angular momentum of the black hole.

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