Results 61 to 70 of about 1,130 (187)
Hard X-ray variability of active galactic nuclei [PDF]
Astronomy & Astrophysics, 2007 Aims. Active Galactic Nuclei are known to be variable throughout the electromagnetic spectrum. An energy domain poorly studied in this respect is the hard X-ray range above 20 keV. Methods. The first 9 months of the Swift/BAT all-sky survey are used to study the 14-195 keV variability of the 44 brightest AGN. The sources have been selected due to their
V. Beckmann +6 more
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The Astrophysical JournalWe present a time-resolved X-ray spectral analysis of the warm absorbers in the Seyfert galaxy NGC 4051, which has an active galactic nucleus (AGN), using observations from the Neutron Star Interior Composition Explorer (NICER).
Dev R. Sadaula +2 more
doaj +1 more source
Geochemistry, Geophysics, Geosystems, Volume 27, Issue 7, July 2026.Abstract Eocene magmatism in southern Tibet records deep geodynamic processes associated with the India‐Asia collision. The Quxu batholith, a representative segment of the Gangdese magmatic belt, hosts widespread mafic microgranular enclaves (MMEs) indicating magma mixing.
Yuanku Meng +5 more
wiley +1 more source
X-ray reverberation in Active Galactic Nuclei
, 2015 Narrow Line Type-1 Seyfert active galaxies can exhibit a high degree of variability in the X-ray regime. This thesis examines that variability in the context of reverberation models, in which a flare in activity has an extended, energy dependent, response. A novel method is developed for estimating the response function in different energy bands.
openaire +2 more sources
Quasiperiodic Oscillation of RE J1034+396 Diagnosed with Phase-resolved Spectral Analysis
The Astrophysical Journal LettersWe analyze 10 XMM-Newton observations of the narrowline Seyfert 1 galaxy RE J1034+396 to investigate the origin of its quasiperiodic oscillation (QPO).
Wen-Zhong Li +11 more
doaj +1 more source
Aircraft Ionizing Radiation Exposure for Solar Cycle 24/25 From ARMAS and NAIRAS
Space Weather, Volume 24, Issue 7, July 2026.Abstract Exposure to ionizing radiation from galactic cosmic rays and solar energetic particles at aviation flight altitudes can have an adverse effect on human health. Although airline crews are classified as radiation workers by the International Commission on Radiological Protection (ICRP), in most countries, their level of exposure is unquantified ...
Daniel B. Phoenix +3 more
wiley +1 more source
The Role of Environment in Triggering Active Galactic Nuclei—Evidence for a Change at z ∼ 1
The Astrophysical JournalWhat triggers active galactic nuclei (AGN) in some galaxies and what role this brief period of activity plays in the overall evolution of galaxies are still open questions. This paper explores whether or not the local, on scales of ≈1 Mpc, galaxy density
Jason R. Reeves +4 more
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New Terrestrial Native Iron Discovered on Earth's Surface
Geochemistry, Geophysics, Geosystems, Volume 27, Issue 7, July 2026.Abstract Native iron is a major common mineral in lunar samples and meteorites but rarely occurs on Earth's surface, as its stability requires highly reducing conditions with very low oxygen fugacity. To date, native iron has mainly been found in basalts, ophiolites, and deep hydrothermal systems.
Tingwei Zhang +5 more
wiley +1 more source
A Systematic Search for X-Ray Eclipse Events in Active Galactic Nuclei Observed by Swift
The Astrophysical JournalThe nuclear regions of active galactic nuclei (AGNs) likely host clumpy clouds that occasionally obscure the central X-ray source, causing eclipse events. These events offer a unique opportunity to study the properties and origins of such clouds. However,
Tianying Lian, Chichuan Jin, Weimin Yuan
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Journal of Geophysical Research: Space Physics, Volume 131, Issue 7, July 2026.Abstract The data from a cosmic ray (CR) detector in Mexico City were collected over a period of 2 years from September 2023 to September 2025, during the maximum phase of Solar Cycle 25. The CR detector consists of an array of scintillators and measures the muonic component of secondary CRs.
D. Martínez‐Montiel +4 more
wiley +1 more source