Results 51 to 60 of about 53,924 (236)

A Comparative Study of VTEC Estimates Derived From S/X VLBI and VGOS Observations

Space Weather, Volume 23, Issue 12, December 2025.
Abstract The ionosphere, which strongly varies in time and space, is one of the largest error sources for microwave measurements, if not accounted for accurately. Especially for single‐frequency observations, precise ionospheric models are needed to correct for the ionospheric delays. This study explores the utility of Very Long Baseline Interferometry
Arno Rüegg, Grzegorz Kłopotek, Benedikt Soja   +2 more
wiley   +1 more source

Can Fractal Dimension Distinguish between Grand-design and Flocculent Spiral Arms?

The Astrophysical Journal
About two-thirds of disk galaxies host spiral arms, ranging from well-delineated grand-design spirals to fragmented flocculent spiral galaxies. We introduce fractal dimension D _B as a nonparametric measure to distinguish between grand-designs and ...
Biju Saha, Subhadip Dutta, Arunima Banerjee   +2 more
doaj   +1 more source

Reverberation mapping of active galactic nuclei: From X-ray corona to dusty torus

iScience, 2021
Summary: The central engines of active galactic nuclei (AGNs) are powered by accreting supermassive black holes, and while AGNs are known to play an important role in galaxy evolution, the key physical processes occur on scales that are too small to be ...
Edward M. Cackett, Misty C. Bentz, Erin Kara   +2 more
doaj   +1 more source

Extragalactic Sources of TeV Gamma Rays: A Summary

, 2003
The development of techniques whereby gamma rays of energy 100 GeV and above can be studied from the ground, using indirect, but sensitive, techniques has opened up a new area of high energy photon astronomy.
Aharonian, Aharonian, Aharonian, Aharonian, Aharonian, Aharonian, Aharonian, Aharonian, Aharonian, Bicknell, Bignami, Boone, Boone, Bradbury, Buckley, Catanese, Chadwick, Costamante, Costamante, D Horan, Djannati-Atai, Djannati-Atai, Djannati-Atai, Gaidos, Giommi, Grindlay, Hartman, Hoffman, Holder, Horan, Itoh, Itoh, Kerrick, Krawczynski, Krennrich, Krennrich, Krennrich, Neshpor, Neshpor, Nishiyama, Petry, Pian, Punch, Quinn, Roberts, Samuelson, Swanenburg, T.C Weekes, Volk, Weekes   +49 more
core   +1 more source

HEAD IN THE STARS, FEET ON THE GROUND: Scale and Astronomy Initiatives in Southern Africa

Cultural Anthropology, Volume 40, Issue 4, Page 571-596, November 2025.
ABSTRACT This article explores the evolution of radio astronomy in South Africa and Madagascar, focusing on how “scale” functions as both a way of understanding the world and marking differences in existence. In outer space research, the ground is crucial but often overlooked.
HANNA NIEBER, DAVIDE CHINIGÒ
wiley   +1 more source

On the Kinematic Nature of Apparent Disks at High Redshifts: Local Counterparts are Not Dominated by Ordered Rotation but by Tangentially Anisotropic Random Motion

The Astrophysical Journal Letters
It is not straightforward to physically interpret the apparent morphology of galaxies. Recent observations by the James Webb Space Telescope (JWST) revealed a dominant galaxy population at high redshifts ( z > 2) that were visually classified as disks ...
Bitao Wang, Yingjie Peng, Michele Cappellari, Hua Gao, Houjun Mo   +4 more
doaj   +1 more source

Deep Space Network Radio Science and Ground‐Based Planetary Radar in the Next Decade

Radio Science, Volume 60, Issue 7, July 2025.
Abstract The Deep Space Network (DSN) has been a core operational element of NASA's crewed and robotic exploration of the Solar System since the early 1960s. The primary role of the DSN has been to acquire telemetry and navigation data, but over the years, its radiometric and radar capabilities have expanded to form a system for obtaining unique ...
R. S. Park, J. E. Riedel, N. Rodriguez‐Alvarez, M. Brozovic, L. A. M. Benner, P. Vergados, D. Buccino, C. S. Jacobs, L. S. Locke, S. W. Asmar, R. Castano, T. J. W. Lazio, J. Jao, C. Lee   +13 more
wiley   +1 more source

On the Age Distribution of Classical Cepheids in the Galaxy

Astronomische Nachrichten, Volume 346, Issue 5, June 2025.
ABSTRACT We revisit the problem of the positive correlation between age and Galactocentric distance seen in Galactic Classical Cepheids, which at first sight may seem counter‐intuitive in the context of inside‐out galaxy formation. To explain it, we use the Besançon Galaxy Model and a simulation of star particles in the Galactic disc coupled with ...
Friedrich Anders, Chloé Padois, Marc Vilanova Sar, Marcin Semczuk, Marc del Alcázar‐Julià, Francesca Figueras   +5 more
wiley   +1 more source

Isolated Neutron Stars as Science Validation for XMM2ATHENA: Ensuring Robust Data for Future X‐Ray Astronomy

Astronomische Nachrichten, Volume 346, Issue 3-4, March-May 2025.
ABSTRACT The discovery of radio‐quiet, x‐ray thermally emitting isolated neutron stars (XINSs) in the ROSAT All‐Sky Survey revealed a previously overlooked component of the neutron star population. Advancements in x‐ray instrumentation and the availability of deep, wide‐area optical surveys now enable us to explore XINSs at fainter x‐ray fluxes and ...
Adriana Mancini Pires, Christian Motch, Axel Schwope, Iris Traulsen, Jean Ballet, Sudip Chakraborty, David Homan, Jan Kurpas, Ada Nebot Gomez‐Moràn, François‐Xavier Pineau, Hugo Tranin, Natalie Webb   +11 more
wiley   +1 more source

Revisiting Galaxy Cluster Scaling Relations through Dark Matter–Gas Coherence: Scatter Dependence on Dynamical State

The Astrophysical Journal
Galaxy clusters, the most massive, dark-matter-dominated, and most recently assembled structures in the Universe, are key tools for probing cosmology.
Giulia Cerini, Elena Bellomi, Nico Cappelluti, Sabina Khizroev, Erwin T. Lau, Priyamvada Natarajan, John ZuHone   +6 more
doaj   +1 more source