scholarly journals The role of electron heating physics in images and variability of the Galactic Centre black hole Sagittarius A*

2018 ◽  
Vol 478 (4) ◽  
pp. 5209-5229 ◽  
Author(s):  
Andrew Chael ◽  
Michael Rowan ◽  
Ramesh Narayan ◽  
Michael Johnson ◽  
Lorenzo Sironi
Keyword(s):  
Black Hole ◽  
Galactic Centre ◽  
Electron Heating ◽  
Sagittarius A

scholarly journals The ecology of the galactic centre: Nuclear stellar clusters and supermassive black holes

2019 ◽  
Vol 14 (S351) ◽  
pp. 80-83 ◽  
Author(s):  
Melvyn B. Davies ◽  
Abbas Askar ◽  
Ross P. Church
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Large Fraction ◽  
Galactic Nuclei ◽  
Supermassive Black Holes ◽  
Galactic Centre ◽  
Stellar Clusters ◽  
Stellar Cluster ◽  
Supermassive Black Hole ◽  
Multiple Clusters

AbstractSupermassive black holes are found in most galactic nuclei. A large fraction of these nuclei also contain a nuclear stellar cluster surrounding the black hole. Here we consider the idea that the nuclear stellar cluster formed first and that the supermassive black hole grew later. In particular we consider the merger of three stellar clusters to form a nuclear stellar cluster, where some of these clusters contain a single intermediate-mass black hole (IMBH). In the cases where multiple clusters contain IMBHs, we discuss whether the black holes are likely to merge and whether such mergers are likely to result in the ejection of the merged black hole from the nuclear stellar cluster. In some cases, no supermassive black hole will form as any merger product is not retained. This is a natural pathway to explain those galactic nuclei that contain a nuclear stellar cluster but apparently lack a supermassive black hole; M33 being a nearby example. Alternatively, if an IMBH merger product is retained within the nuclear stellar cluster, it may subsequently grow, e.g. via the tidal disruption of stars, to form a supermassive black hole.

scholarly journals A cool accretion disk around the Galactic Centre black hole

Nature ◽  
2019 ◽  
Vol 570 (7759) ◽  
pp. 83-86 ◽  
Author(s):  
Elena M. Murchikova ◽  
E. Sterl Phinney ◽  
Anna Pancoast ◽  
Roger D. Blandford
Keyword(s):  
Black Hole ◽  
Accretion Disk ◽  
Galactic Centre

scholarly journals The first law of black hole mechanics in the Einstein-Maxwell theory revisited

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Zachary Elgood ◽  
Patrick Meessen ◽  
Tomás Ortín
Keyword(s):  
Black Hole ◽  
Maxwell Theory ◽  
Gauge Invariant ◽  
Momentum Maps ◽  
Field Strengths

Abstract We re-derive the first law of black hole mechanics in the context of the Einstein-Maxwell theory in a gauge-invariant way introducing “momentum maps” associated to field strengths and the vectors that generate their symmetries. These objects play the role of generalized thermodynamical potentials in the first law and satisfy generalized zeroth laws, as first observed in the context of principal gauge bundles by Prabhu, but they can be generalized to more complex situations. We test our ideas on the d-dimensional Reissner-Nordström-Tangherlini black hole.

scholarly journals Searching for pulsars in future radio continuum surveys

2017 ◽  
Vol 13 (S337) ◽  
pp. 328-329
Author(s):  
Shi Dai ◽  
Simon Johnston ◽  
George Hobbs
Keyword(s):  
Black Hole ◽  
Radio Continuum ◽  
Galactic Centre ◽  
Dispersion Measure ◽  
Millisecond Pulsars ◽  
Square Kilometre Array ◽  
Orbital Modulation ◽  
Pulsar Searches

AbstractRadio continuum surveys are equally sensitive to all pulsars, not affected by dispersion measure smearing, scattering or orbital modulation of spin periods, and therefore allow us to search for extreme pulsars, such as sub-millisecond pulsars, pulsar-black hole systems and pulsars in the Galactic Centre. As we move towards the Square Kilometre Array (SKA) era, searching for pulsars in continuum images will complement conventional pulsar searches, and make it possible to find extreme objects.

scholarly journals TTM Observations of X1755-338

1995 ◽  
Vol 151 ◽  
pp. 334-335
Author(s):  
H.C. Pan ◽  
G.K. Skinner ◽  
R.A. Sunyaev ◽  
K.N. Borozdin
Keyword(s):  
Black Hole ◽  
Energy Resolution ◽  
Space Station ◽  
Galactic Centre ◽  
Imaging Spectrometer ◽  
X Ray ◽  
Black Hole Candidate ◽  
Coded Mask

X1755-338 is an X-ray binary source which displays X-ray dips with a 4.4 hour period (White et al. 1984). It was previously noted as an unusually soft X-ray source by Jones (1977) and was suggested later as a black-hole candidate (BHC) by White & Marshall (1984), and White et al. (1984), based on the similarity of its location in an X-ray colour-colour diagram to that of a group of BHCs.The TTM is a coded-mask imaging spectrometer on board the KVANT module of the MIR space station. It is capable of producing images in the 2 – 30 keV band with an energy resolution of about 18% at 6 keV. The instrumental details are given in Brinkman et al. (1985).We observed X1755-338 in 1989 March-September during the period of the TTM Galactic Centre Survey.

scholarly journals Constraints on ultra-low-frequency gravitational waves with statistics of pulsar spin-down rates

2019 ◽  
Vol 489 (3) ◽  
pp. 3547-3552
Author(s):  
Hiroki Kumamoto ◽  
Yuya Imasato ◽  
Naoyuki Yonemaru ◽  
Sachiko Kuroyanagi ◽  
Keitaro Takahashi
Keyword(s):  
Black Hole ◽  
Gravitational Waves ◽  
Time Derivative ◽  
Low Frequency ◽  
Upper Bounds ◽  
Galactic Centre ◽  
Frequency Range ◽  
Rate Distribution ◽  
Black Hole Binaries ◽  
Supermassive Black Hole

Abstract We probe ultra-low-frequency gravitational waves (GWs) with statistics of spin-down rates of millisecond pulsars (thereafter MSPs) by a method proposed in our previous work. The considered frequency range is 10−12 Hz ≲ fGW ≲ 10−10  Hz . The effect of such low-frequency GWs appears as a bias to spin-down rates that has a quadrupole pattern in the sky. We use the skewness of the spin-down rate distribution and the number of MSPs with negative spin-down rates to search for the bias induced by GWs. Applying this method to 149 MSPs selected from the ATNF pulsar catalogue, we derive upper bounds on the time derivative of the GW amplitudes of $\dot{h} \lt 6.2 \times 10^{-18}~{\rm s}^{-1}$ and $\dot{h} \lt 8.1 \times 10^{-18}~{\rm s}^{-1}$ in the directions of the Galactic Centre and M87, respectively. Approximating the GW amplitude as $\dot{h} \sim 2 \pi f_{\rm GW} h$, the bounds translate into h < 3 × 10−8 and h < 4 × 10−8, respectively, for fGW = 1/(1000 yr). Finally, we give the implications to possible supermassive black hole binaries at these sites.

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