Results 51 to 60 of about 5,650 (230)
Astronomische Nachrichten, Volume 346, Issue 5, June 2025.ABSTRACT Classification of galaxies, stars, and quasars using spectral data is fundamental to astronomy, but often relies heavily on redshift. This study evaluates the performance of 10 machine learning algorithms on SDSS data to classify these objects, with a particular focus on scenarios where redshift information is unavailable.
Debashis Chatterjee, Prithwish Ghosh
wiley +1 more source
Supermassive black holes in galactic bulges [PDF]
Monthly Notices of the Royal Astronomical Society: Letters, 2008 Abstract Growing evidence indicate supermassive black holes (SMBHs) in a mass range of MBH∼ 106–1010 M⊙ lurking in central stellar bulges of galaxies. Extensive observations reveal fairly tight power laws of MBH versus the mean stellar velocity dispersion σ of the host stellar bulge.
Lou, Yu-Qing, Jiang, Yan-Fei
openaire +2 more sources
Stochastic Quantum Mechanics in Curved Spaces: Application to Schwarzschild Black Holes
Astronomische Nachrichten, Volume 346, Issue 3-4, March-May 2025.ABSTRACT In this work, we start from the hypothesis that the universe lives in a Gravitational Wave Background (GWB). From this hypothesis, it follows that space–time is not locally flat because we have to take into account the fluctuations of the GWB in space–time. This implies that sufficiently small particles will feel these oscillations, preventing
Juan S. Jerez‐Rodriguez +1 more
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Interplay of Magnetic Reconnection and Current Sheet Kink Instability in the Earth's Magnetotail
Geophysical Research Letters, Volume 52, Issue 2, 28 January 2025.Abstract Magnetic reconnection and current sheet kink instability often develop concurrently in current sheets, yet their dynamic interplay remains unclear. We investigate their interaction in the magnetotail of a 3D global magnetospheric hybrid‐Vlasov simulation. We identify the instability growth and saturation phase and estimate the evolution of the
G. Cozzani +12 more
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Probing extreme black‐hole outflows on short timescales via high spectral‐resolution x‐ray imagers
Astronomische Nachrichten, Volume 345, Issue 6-7, July-August 2024.Abstract We investigate outflows and the physics of super‐Eddington versus sub‐Eddington regimes in black hole systems. Our focus is on prospective science using next‐generation high‐resolution soft x‐ray instruments. We highlight the properties of black hole ultraluminous x‐ray source (ULX) systems in particular. Owing to scale invariance in accreting
C. Pinto +9 more
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Asymptotically‐Flat Black Hole Solutions in Symmergent Gravity
Fortschritte der Physik, Volume 72, Issue 4, April 2024.Abstract Symmergent gravity is an emergent gravity model with an R+R2$R+R^2$ curvature sector and an extended particle sector having new particles beyond the known ones. With constant scalar curvature, asymptotically flat black hole solutions are known to have no sensitivity to the quadratic curvature term (coefficient of R2$R^2$). With variable scalar
Beyhan Puliçe +3 more
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Gravitational synchrotron radiation and Penrose process in STVG theory
Physics Letters B, 2023 The paper has explored analogue of gravitational synchrotron massive particle and Penrose process in MOdified Gravity (MOG) known as Scalar-Tensor-Vector-Gravity (STVG).
Bobur Turimov +3 more
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Differential rotation in compact objects with hyperons and delta isobars
Astronomische Nachrichten, Volume 345, Issue 2-3, February-March 2024.Abstract Neutron stars may experience differential rotation on short, dynamical timescales following extreme astrophysical events like binary neutron star mergers. In this work, the masses and radii of differentially rotating neutron star models are computed.
Delaney Farrell +3 more
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Gravitational Larmor precession
European Physical Journal C: Particles and Fields, 2023 Inspired by the reported existence of substantive magnetic fields in the vicinity of the central supermassive black holes in Sagittarius A* and Messier 87*, we consider test particle motion in the spacetime close to a generic spherical black hole in the ...
Chandrachur Chakraborty +1 more
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Null Geodesics and Strong Field Gravitational Lensing in a String Cloud Background
Advances in High Energy Physics, 2015 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
M. Sharif, Sehrish Iftikhar
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