Results 71 to 80 of about 152,801 (176)

A Systematic Search for Active Galactic Nuclei Obscuration Variability in the Chandra Archive

open access: yesThe Astrophysical Journal
The nature of the obscuring material in active galactic nuclei (AGN) can be studied by measuring changes in the line-of-sight column density, N _H,LOS , over time. This can be accomplished by monitoring AGN over long periods of time and at all timescales.
Isaiah S. Cox   +7 more
doaj   +1 more source

IceCube Search for Neutrino Emission from X-Ray Bright Seyfert Galaxies

open access: yesThe Astrophysical Journal
The recent IceCube detection of TeV neutrino emission from the nearby active galaxy NGC 1068 suggests that active galactic nuclei (AGNs) could make a sizable contribution to the diffuse flux of astrophysical neutrinos. The absence of TeV γ -rays from NGC
R. Abbasi   +424 more
doaj   +1 more source

Evidence for Neutrino Emission from X-Ray Bright Seyfert Galaxies in the Southern Hemisphere Using Enhanced Starting Track Events with IceCube

open access: yesThe Astrophysical Journal Letters
IceCube recently reported the observation of TeV neutrinos from the nearby Seyfert galaxy NGC 1068, and the corresponding neutrino flux is significantly higher than the upper limit implied by observations of GeV–TeV gamma rays.
R. Abbasi   +430 more
doaj   +1 more source

The shortest detected intra-day variability of active galactic nuclei in the TESS survey

open access: yesAstronomy & Astrophysics
Context. Active galactic nuclei (AGNs) are known to be variable in almost all wavelengths and timescales. The shortest AGN variability timescale can be used to probe the smallest scale structures within AGNs. Aims. We aim to measure the shortest detected
Yuk Heechan   +2 more
doaj   +1 more source

Emission line profiles and X-ray observations of broad and narrow line Seyfert 1 galaxies

open access: yes, 2011
Narrow Line Seyfert 1 galaxies represent a distinct category in the larger family of Type 1 Active Galactic Nuclei. The occurrence of emission line profiles not broader than 2000 km/s, combined with luminosity estimates comparable to those of their broad
CIROI, STEFANO   +5 more
core  

Far-infrared properties of optically-selected quasars and Seyfert galaxies [PDF]

open access: yes, 1987
Pointed IRAS observations and ground based observations are used to determine the infrared properties of optically selected galaxies and quasars. The use of complete, unbiased, optically selected samples means that statistical tests can be applied to ...
Edelson, R. A., Malkan, M. A.
core  

Missing Seyfert Galaxies

open access: yes, 2017
El objetivo de este trabajo es la estimaci´on del n´umero de galaxias Seyfert faltantes debido a la ocultaci´on por el polvo del disco de las galaxias espirales.
Tovmassian, Hrant M., Yam, O.
core  

Two Epochs of VLBI Observations of Eight KISSR Seyfert and LINER Galaxies: Suggestions of Fast and Filamentary Outflows

open access: yesThe Astrophysical Journal
We present here the results from a second epoch of phase-referenced VLBA observations of eight Seyfert and LINER galaxies from the KISSR sample. These sources were chosen based on the presence of double peaks or asymmetries in their emission lines as ...
Preeti Kharb   +6 more
doaj   +1 more source

Modeling Star Formation Histories of Changing-look AGN Host Galaxies with Prospector

open access: yesThe Astrophysical Journal
Changing-look active galactic nuclei (CL-AGNs), are AGNs that appear to transition between Seyfert Type 1 and 2 over periods of months to years. Several mechanisms to trigger these transitions have been proposed, but we have yet to conclusively determine
Margaret E. Verrico   +9 more
doaj   +1 more source

"Velocity Dispersion and Black Hole Mass in Seyfert 1 Galaxies" [PDF]

open access: yes, 2003
Paper presented at Carnegie Observatories Centennial Symposium I - Coevolution of Black Holes and Galaxies, 20-25 October 2002, Carnegie Observatories, Pasadena, CA.Bulge stellar velocity dispersions, sigma, in Seyfert 1 galaxies are combined with the ...
Green, Richard   +4 more
core  

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