Results 101 to 110 of about 9,238,867 (222)
Latitude Survey of Neutrons and Muons to Determine Cosmic Ray Neutron Sensing Yield Functions
Journal of Geophysical Research: Space Physics, Volume 131, Issue 8, August 2026.Abstract Cosmic Ray Neutron Sensing (CRNS) is a ground‐based technique that utilizes epithermal neutron measurements as a proxy for environmental hydrogen content. Similarly to other ground‐based cosmic ray detectors (e.g., neutron monitors), CRNS detectors are affected by the solar cycle and space weather events.
Lasse Hertle +16 more
wiley +1 more source
X-Ray Spectra and Time Variability of Active Galactic Nuclei [PDF]
Annual Review of Astronomy and Astrophysics, 1984 The X-ray spectra of broad line active galactic nuclei (AGN) of all types (Seyfert I's, NELG's, broadline radio galaxies) are well fit by a power law in the .5 to 100 keV band of man energy slope alpha = .68 + or - .15. There is, as yet, no strong evidence for time variability of this slope in a given object.
openaire +1 more source
Optical polarimetry studies of Seyfert galaxies [PDF]
, 1999 Optical imaging polarimetry has been performed on seven nearby Seyfert galaxies, three with face-on and four with edge-on host galaxies of various morphological classifications.
Felton, Michelle Ann
core
Journal of Geophysical Research: Space Physics, Volume 131, Issue 8, August 2026.Abstract Cosmic rays (CRs) are energetic particles originating from galactic and extragalactic sources. When arriving into the solar system and the Sun's heliosphere, they are diverted and modulated by the magnetic activity of the Sun. This modulation can be quantified by the modulation parameter ϕ $\phi $ determined with the Force‐field approximation (
Pauli Väisänen +5 more
wiley +1 more source
The Astrophysical JournalCompton-thick active galactic nuclei (CT-AGNs), which are defined by column density N _H ≥ 1.5 × 10 ^24 cm ^−2 , emit feeble X-ray radiation, even undetectable by X-ray instruments.
Rui Zhang +9 more
doaj +1 more source
Test for Echo: X-Ray Reflection Variability in the Seyfert-2 Active Galactic Nucleus NGC 4388
The Astrophysical JournalWe report on a study of the narrow Fe K α line and reflection spectrum in the well-known Seyfert-2 active galactic nucleus (AGN), NGC 4388. X-ray spectra summed from two extensive NICER monitoring campaigns, separated by years, show strong evidence of ...
Ben Gediman +6 more
doaj +1 more source
The Realm of the First Quasars in the Universe: the X-ray View
, 2007 We review the X-ray studies of the highest redshift quasars, focusing on the results obtained with Chandra and XMM-Newton. Overall, the X-ray and broad-band properties of z>4 quasars and local quasars are similar, suggesting that the small-scale X ...
Schneider D. P. +5 more
core +1 more source
On the Properties of X-Ray Corona in Seyfert 1 Galaxies
The Astrophysical JournalWe carried out a uniform and systematic analysis of a sample of 112 nearby bright Seyfert 1 type active galactic nuclei, the observations of which were carried out by the Nuclear Spectroscopic Telescope Array between 2013 August and 2022 May.
Indrani Pal +6 more
doaj +1 more source
The Astrophysical JournalWe present serendipitous simultaneous radio and X-ray light curves of the dwarf Seyfert galaxy UGC 6728 spanning 5 yr. The X-ray light curve exhibits a flaring period, followed by a gradual rise and decline.
Krista Lynne Smith +2 more
doaj +1 more source
The Astrophysical JournalWe present a detailed analysis of the most luminous and obscured active galactic nuclei (AGNs) detected in the ultra-hard X-ray band (14–195 kev) by the Swift/Burst Alert Telescope. Our sample comprises 21 X-ray luminous ( ${\mathrm{log}}\,{L}_{{\rm{X}}}/
Alessandro Peca +23 more
doaj +1 more source