Results 81 to 90 of about 2,382,221 (211)

Redshift‐Agnostic Machine Learning Classification: Unveiling Peak Performance in Galaxy, Star, and Quasar Classification (Using SDSS DR17)

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

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, Tonatiuh Matos   +1 more
wiley   +1 more source

Non-linearly scalarized supermassive black holes

European Physical Journal C: Particles and Fields
In this study, we investigate a nonlinear mechanism driving the formation of scalarized rotating black holes within a scalar-Gauss–Bonnet gravity framework that includes an additional squared Gauss–Bonnet term.
Shoupan Liu, Yunqi Liu, Yan Peng, Cheng-Yong Zhang   +3 more
doaj   +1 more source

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, M. Alho, I. Zaitsev, H. Zhou, S. Hoilijoki, L. Turc, M. Grandin, K. Horaites, M. Battarbee, Y. Pfau‐Kempf, U. Ganse, K. Papadakis, M. Palmroth   +12 more
wiley   +1 more source

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, J. F. Steiner, A. Bodaghee, P. Chakraborty, M. Sobolewska, D. R. Pasham, A. Ogorzalek, J. Zuhone, A. Bogdan, M. Vogelsberger   +9 more
wiley   +1 more source

On the location of the supermassive black hole in CTA 102 [PDF]

Astronomy & Astrophysics, 2015
Relativistic jets in active galactic nuclei represent one of the most powerful phenomena in the Universe. They form in the surroundings of the supermassive black holes as a by-product of accretion onto the central black hole in active galaxies. The flow in the jets propagates at velocities close to the speed of light.
Fromm, Christian M., Perucho, Manel, Ros, Eduardo, Savolainen, Tuomas, Zensus, J. Anton   +4 more
openaire   +5 more sources

The Cosmic History of Black Hole Growth from Deep Multiwavelength Surveys

Advances in Astronomy, 2012
Significant progress has been made in the last few years on understanding how supermassive black holes form and grow. In this paper, we begin by reviewing the spectral signatures of active galactic nuclei (AGN) ranging from radio to hard X-ray ...
Ezequiel Treister, C. Megan Urry
doaj   +1 more source

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, Reggie C. Pantig, Ali Övgün, Durmuş Demir   +3 more
wiley   +1 more source

A NORMAL SUPERMASSIVE BLACK HOLE IN NGC 1277 [PDF]

The Astrophysical Journal, 2016
ABSTRACT The identification of galaxies with “overly massive” black holes requires two measurements: a black hole mass (M bh) and a host spheroid mass ( ). Here we provide our measurements for NGC 1277.
Alister W. Graham, Mark Durré, Giulia A. D. Savorgnan, Anne M. Medling, Dan Batcheldor, Nicholas Scott, Beverly Watson, Alessandro Marconi   +7 more
openaire   +5 more sources

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, Fridolin Weber, Jia Jie Li, Armen Sedrakian   +3 more
wiley   +1 more source