Related papers: New AGNs discovered by H.E.S.S

The evidence for multi-messenger photon and neutrino emission from the blazar TXS 0506+056 has demonstrated the importance of realtime follow-up of neutrino events by various ground- and space-based facilities. The effort of H.E.S.S. and…

Blazars, a class of Active Galactic Nuclei (AGN) characterized by a close orientation of their relativistic outflows (jets) towards the line of sight, are a well established extragalactic TeV $\gamma$-ray emitters. Since 2006, three nearby…

Recent observations have revealed an interesting active galactic nuclei (AGN) subclass that shows strong activity at large scales ($\sim1$ kpc) but weaker at small scales ($<10$ pc), suggesting a strong change in the mass accretion rate of…

VERITAS began full-scale operations in 2007 and it remains one of the world's most sensitive very-high-energy (VHE; E >100 GeV) gamma-ray observatories. More than 8,300 hours (~50%) of its good-weather data were targeted on active galactic…

The H.E.S.S. telescope array has observed the complex Monoceros Loop SNR/Rosette Nebula region which contains unidentified high energy EGRET sources and potential very-high-energy (VHE) gamma-ray source. We announce the discovery of a new…

We report the discovery of an Active Galactic Nucleus (AGN) in the nearby SAd galaxy NGC 3621 using Spitzer high spectral resolution observations. These observations reveal the presence of [NeV] 14 um and 24 um emission which is centrally…

Changing-look Active Galactic Nuclei (CL AGNs) exhibit drastic variations in broad emission lines (BELs), the mechanism of which remains unclear. Expanding the sample of CL AGNs is helpful to reveal the mechanism. This study aims to…

The ANTARES telescope has the opportunity to detect transient neutrino sources, such as gamma-ray bursts (GRBs), core-collapse supernovae (SNe), flares of active galactic nuclei (AGNs)... To enhance the sensitivity to these sources, we are…

Blazars, a type of active galactic nuclei (AGN) with relativistic jets pointed at the observer, exhibit flux variability across the electromagnetic spectrum due to particle acceleration in their jets. Power spectral density (PSD) studies…

We report the discovery using Spitzers high resolution spectrograph of 7 Active Galactic Nuclei (AGN) in a sample of 32 late-type galaxies that show no definitive signatures of AGN in their optical spectra. Our observations suggest that the…

We present the results of our identification of eight objects from a preliminary catalogue of X-ray sources detected in the 4-12 keV energy band by the Mikhail Pavlinsky ART-XC telescope aboard the SRG observatory during its first all-sky…

Several newly discovered very-high-energy (VHE; E > 100 GeV) gamma-ray sources in the Galaxy are thought to be associated with energetic pulsars. Among them, middle-aged (> 1E+4 yr) systems exhibit large centre-filled VHE nebulae, offset…

We present multi-frequency (5-345 GHz) and multi-resolution radio observations of 1ES 1927+654, widely considered one of the most unusual and extreme changing-look active galactic nuclei (CL-AGN). The source was first designated a CL-AGN…

We here report a spectroscopic identification of two new changing-look AGNs (CL-AGNs): SDSS\,J104705.16+544405.8 and SDSS\,J120447.91+170256.8 both with a "turn-off" type transition from type 1 to type 1.8/1.9. The identification is arrived…

On 2017 September 22 the IceCube neutrino observatory detected a track-like, very-high-energy event (IceCube-170922A) that is spatially associated with TXS 0506+056, a quasar at a redshift of $z=0.3365$. This source is characterized by the…

Within the framework of our program (running since 2004) of identification of hard X-ray INTEGRAL sources through optical spectroscopy, we present the results concerning the nature of 33 high-energy objects. The data were acquired with the…

The BL Lacertae (BL Lac) object 1ES 2344+514 (1ES 2344), at a redshift of 0.044, was discovered as a source of very high energy (VHE) gamma rays by the Whipple Collaboration in 1995 \citep{2344Catanese98}. This detection was recently…

The Swift Burst Alert Telescope (BAT) is discovering interesting new objects while monitoring the sky in the 14-195 keV band. Here we present the X-ray properties and spectral energy distributions for two unusual AGN sources. Both NVSS…

We report an Active Galactic Nucleus (AGN) with extremely high equivalent width (EW), EW(LyA+NV,rest)>921 AA in the rest-frame, at z~2.24 in the Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX) as a representative case of the…

Results are presented of extended and refined optical identification of 181 radio/X-ray sources in the RASS-Green Bank (RGB) catalog which have been spectroscopically observed in the Sloan digital sky survey (SDSS) DR5. For 72 sources, the…