144 citations · 419 across the 18 of their papers we have counts for
18 papers
In the Eye of the Storm: The Third Giant X-ray Outburst of the Extreme Changing-look AGN IC 3599
D. Grupe, S. Komossa, W. Zheng +10
We report the discovery and multiwavelength follow-up observations of a giant (factor >100) X-ray outburst of the exceptional changing-look active galactic nucleus (AGN) IC 3599. T…
Variability of the X-ray obscuring wind in Mrk 335 with XMM-Newton/RGS
Daniele Rogantini, Erin Kara, Luigi Gallo +10
Transient X-ray obscuration in Seyfert 1 galaxies likely arises from clumpy accretion-disk winds near the broad-line region (BLR), but the wind structure and short-timescale variab…
SVOM discovery of a strong X-ray outburst of the blazar 1ES~1959+650 and multi-wavelength follow-up with the Neil Gehrels Swift observatory
A. Foisseau, A. Coleiro, S. Komossa +37
On December 6, 2024, 1ES 1959+650, one of the X-ray brightest blazars known, underwent a high-amplitude X-ray outburst detected by SVOM, the first such discovery with this mission.…
Extreme line profile variations in the repeating changing-look active galactic nucleus IRAS23226-3843
Wolfram Kollatschny, Dirk Grupe, Hartmut Winkler +7
IRAS23226-3843 has been identified as a highly variable Seyfert galaxy and even as a changing-look active galactic nucleus based on optical spectra. Here we present follow-up obser…
Double-peaked Ca II traces a relativistic broad-line region disk in NGC 4593
M. W. Ochmann, P. M. Weilbacher, M. A. Probst +7
Double-peaked emission lines are observed in a small percentage of active galactic nuclei (AGN). These lines allow the determination of properties of the line-emitting region, know…
Narrow-Line Seyfert 1 Galaxies Beyond the Local X-ray Universe: An X-ray spectral sample
Jiachen Jiang, Dominic J. Walton, Luigi C. Gallo +8
Narrow-line Seyfert 1 AGNs (NLS1s) represent a unique stage in the black hole growth history, characterised by low black hole masses of approximately - solar masses…
The extremes of AGN variability: outbursts, deep fades, changing looks, exceptional spectral states, and semi-periodicities
S. Komossa, D. Grupe, P. Marziani +16
The extremes of Active Galactic Nuclei (AGN) variability offer valuable new insights into the drivers and physics of AGN. We discuss some of the most extreme cases of AGN variabili…
First deep X-ray observations of the Fermi-detected steep-spectrum source and radio-loud NLS1 galaxy 3C 286
Su Yao, S. Komossa, A. Kraus +1
A well-known calibrator source in radio astronomy, 3C 286 (), is a compact steep-spectrum (CSS) radio source and spectroscopically classified as a narrow-line Seyfert 1 (NL…
On the nature of the radio calibrator and gamma-ray emitting NLS1 galaxy 3C 286 and its multiwavelength variability
S. Komossa, S. Yao, D. Grupe +1
The quasar 3C 286, a well-known calibrator source in radio astronomy, was found to exhibit exceptional multiwavelength properties. Its rich and complex optical emission-line spectr…
A Hot Mess: The Rich and Complex Soft Emitting Regions Surrounding the Reflection Dominated Flaring Central Engine of Mrk 1239
Margaret Z. Buhariwalla, L. C. Gallo, J. Mao +5
Previous X-ray works on Mrk 1239 have revealed a complex Narrow Line Seyfert 1 (NLS1) that exhibits substantial absorption and strong emission from both collisional (CIE) and photo…
The calm before the (next) storm: no third outburst in 2019--2020, and ongoing monitoring of the transient AGN IC 3599
Dirk Grupe, S. Komossa, Salem Wolsing
We report on follow-up observations of the Seyfert 1.9 galaxy IC 3599 with the NASA Neil Gehrels Swift mission. The detection of a second X-ray outburst in 2010 by Swift after the…
The transient event in NGC 1566 from 2017 to 2019 -- I. An eccentric accretion disk and a turbulent, disk-dominated broad-line region unveiled by double-peaked Ca II and O I lines
M. W. Ochmann, W. Kollatschny, M. A. Probst +12
NGC 1566 is known for exhibiting recurrent outbursts, which are accompanied by changes in spectral type. The most recent transient event occurred from 2017 to 2019 and was reported…
Changing-look NLS1 galaxies, their detection with SVOM, and the case of NGC 1566
D. W. Xu, S. Komossa, D. Grupe +15
We discuss applications of the study of the new and barely explored class of changing-look (CL) narrow-line Seyfert 1 (NLS1) galaxies and comment on their detection with the space…
The Collisional and Photoionized Plasma in the Polarized NLS1 galaxy Mrk 1239
Margaret Z. Buhariwalla, Luigi C. Gallo, J. Mao +4
Mrk 1239 is a highly polarized NLS1 in the optical band, whose keV spectrum has remained remarkably consistent over more than two decades of observation. Previous analysis…
The NuSTAR spectrum of Mrk 335: Extreme relativistic effects within 2 gravitational radii of the event horizon?
M. L. Parker, D. R. Wilkins, A. C. Fabian +18
We present 3-50 keV NuSTAR observations of the AGN Mrk 335 in a very low flux state. The spectrum is dominated by very strong features at the energies of the iron line at 5-7 keV a…
A blurred reflection interpretation for the intermediate flux state in Mrk 335
L. C. Gallo, A. C. Fabian, D. Grupe +7
As part of a long term monitoring campaign of Mrk 335, deep XMM-Newton observations catch the narrow-line Seyfert 1 galaxy (NLS1) in a complex, intermediate flux interval as the ac…
1H0707-495 in 2011: An X-ray source within a gravitational radius of the event horizon
A. C. Fabian, A. Zoghbi, D. Wilkins +8
The Narrow Line Seyfert 1 Galaxy 1H0707-495 went in to a low state from 2010 December to 2011 February, discovered by a monitoring campaign using the X-Ray Telescope on the Swift s…
Studying X-ray reprocessing and continuum variability in quasars: PG 1211+143
R. Bachev, D. Grupe, S. Boeva +5
We present the results from a monitoring campaign of the Narrow-Line Seyfert~1 galaxy PG 1211+143. The object was monitored with ground-based facilities (UBVRI photometry; from Feb…