Results 31 to 40 of about 53,761 (176)

A Direct Stellar Metallicity Determination in the Disk of the Maser Galaxy NGC4258 [PDF]

, 2013
We present the first direct determination of a stellar metallicity in the spiral galaxy NGC4258 (D=7.6 Mpc) based on the quantitative analysis of a low-resolution (~5 AE) Keck LRIS spectrum of a blue supergiant star located in its disk.
Bresolin, Fabio, Gazak, J. Zachary, Hosek, Matthew W., Kudritzki, Rolf-Peter, Macri, Lucas, Przybilla, Norbert, Urbaneja, Miguel A.   +6 more
core   +3 more sources

Reduced Geomagnetic Shielding During the Laschamps Excursion and Its Impact on Cosmic‐Ray‐Induced Atmospheric Radiation

Journal of Geophysical Research: Space Physics, Volume 131, Issue 2, February 2026.
Abstract The Laschamps geomagnetic excursion (≈41,000 years BP) was a period of significant weakening and incomplete reversal of the Earth's magnetic field. The weakening substantially reduced geomagnetic shielding against cosmic rays (CRs), which contribute to phenomena at Earth, such as cosmogenic isotope production, and atmospheric ionisation and ...
N. Larsen, I. Usoskin, A. Mishev, S. Koldobskiy, P. Väisänen   +4 more
wiley   +1 more source

The Chinese Radio Telescope Array for Interplanetary Scintillation Monitoring

Space Weather, Volume 24, Issue 1, January 2026.
Abstract Solar flares, coronal mass ejections (CMEs) and enegertic particles, etc., are the driving sources that may cause catastrophic space weathers. It is desirable to obtain information of solar eruptions like flares and CMEs, etc., propagating from the Sun to the near‐Earth space.
Yihua Yan, Wei Wang, Jin Fan, Ming Xiong, Zhijun Chen, Linjie Chen, Cang Su, Sha Li, Jun Cheng, Jing Du, Xueshang Feng   +10 more
wiley   +1 more source

The Stochastic‐Dissipative Störmer Problem‐Trajectories and Radiation Patterns

Annalen der Physik, Volume 537, Issue 12, December 2025.
We consider charged particle motion and radiation in a dipole magnetic field, in the presence of friction and of stochastic forces. The numerical solutions of the Langevin equation reveal how these forces modify the complex dynamics of particles, and they offer some new insights into the nonlinear processes relevant to planetary radiation belts ...
Tiberiu Harko, Gabriela Raluca Mocanu
wiley   +1 more source

Synchrotron and Compton Components and their Variability in BL Lac Objects

, 2000
BL Lacertae objects are extreme extragalactic sources characterized by the emission of strong and rapidly variable nonthermal radiation over the entire electromagnetic spectrum.
Ghisellini, G., Giommi, P., Padovani, P., Tagliaferri, G.   +3 more
core   +2 more sources

Fast Radio Burst Discovered in the Arecibo Pulsar ALFA Survey [PDF]

, 2014
Recent work has exploited pulsar survey data to identify temporally isolated, millisecond-duration radio bursts with large dispersion measures (DMs). These bursts have been interpreted as arising from a population of extragalactic sources, in which case ...
Allen, B., Aulbert, C., Bogdanov, S., Brazier, A., Camilo, F., Chatterjee, S., Cordes, J. M., Crawford, F., Deneva, J. S., Fehrmann, H., Freire, P. C. C., Hessels, J. W. T., Jenet, F. A., Karako-Argaman, C., Kaspi, V. M., Knispel, B., Lazarus, P., Lee, K. J., Lorimer, D. R., Lynch, R., Lyne, A. G., McLaughlin, M. A., Ransom, S. M., Scholz, P., Siemens, X., Spitler, L. G., Stairs, I. H., Stovall, K., Swiggum, J. K., van Leeuwen, J., Venkataraman, A., Wharton, R. S., Zhu, W. W.   +32 more
core   +4 more sources

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

Opacity in compact extragalactic radio sources and its effect on radio-optical reference frame alignment [PDF]

, 2007
Accurate alignment of the radio and optical celestial reference frames requires detailed understanding of physical factors that may cause offsets between the positions of the same object measured in different spectral bands.
A. B. Pushkarev, A. P. Lobanov, Böttcher, J. A. Zensus, Kadler, Lara, Lestrade, Lobanov, Y. Y. Kovalev   +8 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

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