scholarly journals New bow-shock source with bipolar morphology in the vicinity of Sgr A*

2019 ◽  
Vol 624 ◽  
pp. A97 ◽  
Author(s):  
F. Peißker ◽  
M. Zajaček ◽  
A. Eckart ◽  
N. B. Sabha ◽  
B. Shahzamanian ◽  
...  
Keyword(s):  
Black Hole ◽  
Line Emission ◽  
Bow Shock ◽  
Emission Source ◽  
Data Sets ◽  
Shock Source ◽  
Young Stellar Object ◽  
Supermassive Black Hole ◽  
Bipolar Outflow ◽  
Sgr A

Context. We find an extended source in the direct vicinity of Sgr A* with an approximate projected mean distance of 425 ± 26 mas. Its sky-projected elongated shape can be described by an averaged spatial extension ofx = 110 ± 20 mas andy = 180 ± 20 mas. With this, the observed object points in the analyzed SINFONI data sets between 2006 and 2016 directly toward the supermassive black hole. We discuss different possible scenarios that could explain the detected blueshifted line emission source.Aims. Here we present a detailed and extensive analysis of the adaptive optics corrected SINFONI data between 2006 and 2016 with a spatial pixel scale of 0.″025 and a corresponding field of view of 0.″8 × 0.″8 per single data cube with the focus on the newly discovered source. We spectroscopically identify the source, which we name X8, in the blueshifted Brγline maps. Additionally, an upper limit for the continuum magnitude can be derived from the close-by S-star S41.Methods. We applied the standard reduction procedure with the SINFONI/EsoRex pipeline for the analysis. We applied pre- and post-data correction in order to establish various calibration procedures. For the sharpened images, we used the Lucy–Richardson algorithm with a low iteration number. For the high-pass filtered images, we used the smooth-subtracting process in order to increase the signal-to-noise ratio.Results. We are able to detect the elongated line emission source in quantified data sets between 2006 and 2016. We find a lower limit for the infrared continuum magnitude ofKs ≳ 17.0 ± 0.1. The alignment of X8 toward Sgr A* can be detected in data sets that fulfill a sufficient number of observations with a defined quality level. A more detailed analysis of the results shows indications of a bipolar outflow source that might be associated with either a young stellar object, or with a post-AGB star or young planetary nebula.Conclusions. The near-infrared excess source X8 close to S24, S25, and S41 can be detected between 2006 and 2016. In addition to an apparent bow-shock morphology, the source shows clear signatures of a bipolar outflow that is consistent with both a young stellar object and a post-AGB star. If confirmed, this would be the closest ever detected bipolar outflow source to the supermassive black hole. Similar to the case of the DSO/G2 source and other dusty sources, it further supports the in situ star formation in the direct vicinity of Sgr A*. If X8 were a bow-shock source, it would be the third object of this type that can be found in projection in the mini-cavity. This scenario would support the idea that the cavity is created by a wind from Sgr A*.

scholarly journals A new MIR bow shock source in the Galactic center

2013 ◽  
Vol 9 (S303) ◽  
pp. 150-152 ◽  
Author(s):  
N. Sabha ◽  
M. Zamaninasab ◽  
A. Eckart ◽  
L. Moser
Keyword(s):  
Black Hole ◽  
Symmetry Axis ◽  
Galactic Center ◽  
Bow Shock ◽  
Shock Source ◽  
Stellar Cluster ◽  
Supermassive Black Hole ◽  
Sgr A ◽  
Central Parsec

AbstractWe find a convex-like feature at a distance of 0.68 pc (17″) from the position of the supermassive black hole, Sgr A*, at the center of the nuclear stellar cluster. This feature resembles a stellar bow shock with a symmetry axis pointing to the center. We discuss the possible nature of the feature and the implications of its alignment with other dusty comet-like objects inside the central parsec.

scholarly journals Sgr A West in the light of molecules: cold and dense gas east of the circumnuclear disk

2013 ◽  
Vol 9 (S303) ◽  
pp. 86-88 ◽  
Author(s):  
Lydia Moser ◽  
A. Eckart ◽  
A. Borkar ◽  
M. García-Marin ◽  
D. Kunneriath ◽  
...  
Keyword(s):  
Black Hole ◽  
Star Formation ◽  
Molecular Clouds ◽  
Near Infrared ◽  
Line Emission ◽  
Dense Gas ◽  
Dark Clouds ◽  
Supermassive Black Hole ◽  
Circumnuclear Disk ◽  
Sgr A

AbstractWe present the very first detection of N2H+J = (1 – 0) and CH3OH(2k−1k) line emission on 5″ scales in the circumnuclear disk (CND) around Sgr A*. The emission matches the position and shape of the dark clouds in the near-infrared. Our findings suggest that these molecular clouds in the eastern CND are significantly colder and denser than the rest of the CND, and partially shocked. The research on these dark clouds will contribute to understanding the processes of star formation close to a supermassive black hole.

scholarly journals Glimpses of the past activity of Sgr A★ inferred from X-ray echoes in Sgr C

2018 ◽  
Vol 610 ◽  
pp. A34 ◽  
Author(s):  
D. Chuard ◽  
R. Terrier ◽  
A. Goldwurm ◽  
M. Clavel ◽  
S. Soldi ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Black Hole ◽  
Monte Carlo Model ◽  
Line Of Sight ◽  
X Rays ◽  
X Ray ◽  
Supermassive Black Hole ◽  
The Past ◽  
Sgr A ◽  
Past Activity

Context. For a decade now, evidence has accumulated that giant molecular clouds located within the central molecular zone of our Galaxy reflect X-rays coming from past outbursts of the Galactic supermassive black hole. However, the number of illuminating events as well as their ages and durations are still unresolved questions. Aims. We aim to reconstruct parts of the history of the supermassive black hole Sgr A★ by studying this reflection phenomenon in the molecular complex Sgr C and by determining the line-of-sight positions of its main bright substructures. Methods. Using observations made with the X-ray observatories XMM-Newton and Chandra and between 2000 and 2014, we investigated the variability of the reflected emission, which consists of a Fe Kα line at 6.4 keV and a Compton continuum. We carried out an imaging and a spectral analysis. We also used a Monte Carlo model of the reflected spectra to constrain the line-of-sight positions of the brightest clumps, and hence to assign an approximate date to the associated illuminating events. Results. We show that the Fe Kα emission from Sgr C exhibits significant variability in both space and time, which confirms its reflection origin. The most likely illuminating source is Sgr A★. On the one hand, we report two distinct variability timescales, as one clump undergoes a sudden rise and fall in about 2005, while two others vary smoothly throughout the whole 2000–2014 period. On the other hand, by fitting the Monte Carlo model to the data, we are able to place tight constraints on the 3D positions of the clumps. These two independent approaches provide a consistent picture of the past activity of Sgr A★, since the two slowly varying clumps are located on the same wavefront, while the third (rapidly varying) clump corresponds to a different wavefront, that is, to a different illuminating event. Conclusions. This work shows that Sgr A★ experienced at least two powerful outbursts in the past 300 yrs, and for the first time, we provide an estimation of their age. Extending this approach to other molecular complexes, such as Sgr A, will allow this two-event scenario to be tested further.

scholarly journals Testing the No-Hair Theorem with Sgr A*

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Tim Johannsen
Keyword(s):  
Black Hole ◽  
Free Parameter ◽  
Milky Way ◽  
Very Long Baseline Interferometry ◽  
Angular Size ◽  
High Brightness ◽  
Supermassive Black Hole ◽  
Long Baseline ◽  
Nearby Stars ◽  
Sgr A

The no-hair theorem characterizes the fundamental nature of black holes in general relativity. This theorem can be tested observationally by measuring the mass and spin of a black hole as well as its quadrupole moment, which may deviate from the expected Kerr value. Sgr A*, the supermassive black hole at the center of the Milky Way, is a prime candidate for such tests thanks to its large angular size, high brightness, and rich population of nearby stars. In this paper, I discuss a new theoretical framework for a test of the no-hair theorem that is ideal for imaging observations of Sgr A* with very long baseline interferometry (VLBI). The approach is formulated in terms of a Kerr-like spacetime that depends on a free parameter and is regular everywhere outside of the event horizon. Together with the results from astrometric and timing observations, VLBI imaging of Sgr A* may lead to a secure test of the no-hair theorem.

scholarly journals Mini-spiral as source of material for Sgr A* in bright state

2012 ◽  
Vol 8 (S290) ◽  
pp. 199-200 ◽  
Author(s):  
Bozena Czerny ◽  
Vladimír Karas ◽  
Devaky Kunneriath ◽  
Tapas K. Das
Keyword(s):  
Black Hole ◽  
Angular Momentum ◽  
Molecular Clouds ◽  
Galactic Center ◽  
Supermassive Black Hole ◽  
The Past ◽  
Accretion Process ◽  
Ring Mode ◽  
Sgr A ◽  
Bright Phase

AbstractThe question of the origin of the gas supplying the accretion process is pertinent especially in the context of enhanced activity of Galactic Center during the past few hundred years, seen now as echo from the surrounding molecular clouds, and the currently observed new cloud approaching Sgr A*. We discuss the so-called Galactic Center mini-spiral as a possible source of material feeding the supermassive black hole on a 0.1 parsec scale. The collisions between individual clumps reduce their angular momentum. and set some of the clumps on a plunging trajectory.We conclude that the amount of material contained in the mini-spiral is sufficient to sustain the luminosity of Sgr A* at the required level. The accretion episodes of relatively dense gas from the mini-spiral passing through a transient ring mode at ~ 104 Rg provide a viable scenario for the bright phase of Galactic Center.

scholarly journals Simulations of M87 and Sgr A* imaging with the Millimetron Space Observatory on near-Earth orbits

2020 ◽  
Vol 500 (4) ◽  
pp. 4866-4877
Author(s):  
A S Andrianov ◽  
A M Baryshev ◽  
H Falcke ◽  
I A Girin ◽  
T de Graauw ◽  
...  
Keyword(s):  
Black Hole ◽  
Space Mission ◽  
Dynamic Imaging ◽  
Image Resolution ◽  
Fast Time ◽  
Supermassive Black Hole ◽  
Long Baseline ◽  
Vlbi Observations ◽  
Sgr A ◽  
Earth Orbits

ABSTRACT High-resolution imaging of supermassive black hole shadows is a direct way to verify the theory of general relativity under extreme gravity conditions. Very Long Baseline Interferometry (VLBI) observations at millimetre/submillimetre wavelengths can provide such angular resolution for the supermassive black holes located in Sgr A* and M87. Recent VLBI observations of M87 with the Event Horizon Telescope (EHT) have shown such capabilities. The maximum obtainable spatial resolution of the EHT is limited by the Earth's diameter and atmospheric phase variations. In order to improve the image resolution, longer baselines are required. The Radioastron space mission successfully demonstrated the capabilities of space–Earth VLBI with baselines much longer than the Earth's diameter. Millimetron is the next space mission of the Russian Space Agency and will operate at millimetre wavelengths. The nominal orbit of the observatory will be located around the Lagrangian L2 point of the Sun–Earth system. In order to optimize the VLBI mode, we consider a possible second stage of the mission that could use a near-Earth high elliptical orbit (HEO). In this paper, a set of near-Earth orbits is used for synthetic space–Earth VLBI observations of Sgr A* and M87 in a joint Millimetron and EHT configuration. General relativistic magnetohydrodynamic models for the supermassive black hole environments of Sgr A* and M87 are used for static and dynamic imaging simulations at 230 GHz. A comparison preformed between ground and space–Earth baselines demonstrates that joint observations with Millimetron and EHT significantly improve the image resolution and allow the EHT + Millimetron to obtain snapshot images of Sgr A*, probing the dynamics at fast time-scales.

scholarly journals The fate of binary stars hosting planets upon interaction with Sgr A* black hole

2020 ◽  
Vol 496 (2) ◽  
pp. 1545-1553
Author(s):  
R Capuzzo-Dolcetta ◽  
N Davari
Keyword(s):  
Black Hole ◽  
High Precision ◽  
Binary Stars ◽  
Binary Star ◽  
Planetary Systems ◽  
The Other ◽  
Supermassive Black Hole ◽  
Massive Object ◽  
Close Interaction ◽  
Sgr A

ABSTRACT Our Galaxy hosts a very massive object at its centre, often referred to as the supermassive black hole Sgr A*. Its gravitational tidal field is so intense that it can strip apart a binary star passing its vicinity and accelerate one of the components of the binary as hypervelocity star (HVS) and grab the other star as S-star. Taking into consideration that many binary star systems are known to host planets, in this paper we aim to broaden the study of the close interaction of binary stars and their planetary systems with Sgr A* massive object. Results are obtained via a high-precision N-body code including post-Newtonian approximation. We quantify the likelihood of capture and ejection of stars and planets after interaction with Sgr A*, finding that the fraction of stars captured around it is about three times that of the planets (∼49.4 per cent versus ∼14.5 per cent) and the fraction of hypervelocity planet ejection is about twice that of HVSs (∼21.7 per cent versus ∼9.0 per cent). The actual possibility of observational counterparts deserves further investigation.

scholarly journals IS THERE A SUPERMASSIVE BLACK HOLE AT THE CENTER OF THE MILKY WAY?

2009 ◽  
Vol 18 (06) ◽  
pp. 889-910 ◽  
Author(s):  
MARK J. REID
Keyword(s):  
Black Hole ◽  
Radio Source ◽  
Milky Way ◽  
Mass Density ◽  
Apparent Size ◽  
Central Mass ◽  
Infrared Wavelength ◽  
Supermassive Black Hole ◽  
Focal Position ◽  
Sgr A

This review outlines the observations that now provide an overwhelming scientific case that the center of the Milky Way harbors a supermassive black hole. Observations at infrared wavelength trace stars that orbit about a common focal position and require a central mass (M) of 4 × 106 M⊙ within a radius of 100 AU. Orbital speeds have been observed to exceed 5,000 km s-1. At the focal position there is an extremely compact radio source (Sgr A*), whose apparent size is near the Schwarzschild radius (2GM/c2). This radio source is motionless at the ~ 1 km s-1 level at the dynamical center of the Galaxy. The mass density required by these observations is now approaching the ultimate limit of a supermassive black hole within the last stable orbit for matter near the event horizon.

scholarly journals Acceleration of particles up to PeV energies at the galactic centre

2016 ◽  
Vol 12 (S324) ◽  
pp. 317-321
Author(s):  
Stefano Gabici ◽  
Felix A. Aharonian ◽  
Emmanuel Moulin ◽  
Aion Viana
Keyword(s):  
Black Hole ◽  
High Energy ◽  
Galactic Cosmic Rays ◽  
Galactic Centre ◽  
Acceleration Of Particles ◽  
Supermassive Black Hole ◽  
Centre Region ◽  
Very High Energy ◽  
Sgr A ◽  
Very High

AbstractRecent very high energy observations of the galactic centre region performed by H.E.S.S. revealed the presence of a powerful PeVatron. This is the first of such objects detected, and its most plausible counterpart seems to be associated to Sgr A*, the supermassive black hole in the centre of our galaxy. The implications of this discovery will be discussed, in particular in the context of the problem of the origin of galactic cosmic rays.

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