Explanipedia

Combined dark matter search towards dwarf spheroidal galaxies with Fermi-LAT, HAWC, H.E.S.S., MAGIC, and VERITAS Open

S. Abdollahi, L Baldini, R Bellazzini, B. Berenji, E. Bissaldi , et al. · 2025

Dwarf spheroidal galaxies (dSphs) are excellent targets for indirect dark matter (DM) searches using gamma-ray telescopes because they are thought to have high DM content and a low astrophysical background. The sensitivity of these searche…

Fermi detection of gamma-ray emission from the hot coronae of radio-quiet active galactic nuclei Open

Junrong Liu, Jian‐Min Wang, Soheila Abdollahi, M. Ajello, Rafael Alves Batista , et al. · 2025

VLBA observations of a sample of low-power compact symmetric objects Open

M. Orienti, F. D'Ammando, D. Dallacasa, Giulia Migliori, P. Rossi , et al. · 2025

Compact symmetric objects (CSOs) are intrinsically compact extragalactic radio sources that are thought to be the progenitors of classical radio galaxies. To date, evolutionary models have mainly focused on the formation and growth of high…

VLBA observations of a sample of low-power compact symmetric objects Open

M. Orienti, F. D'Ammando, D. Dallacasa, Giulia Migliori, P. Rossi , et al. · 2025

Compact symmetric objects (CSOs) are intrinsically compact extragalactic radio sources that are thought to be the progenitors of classical radio galaxies. To date, evolutionary models have mainly focused on the formation and growth of high…

GRB 221009A: The B.O.A.T. Burst that Shines in Gamma Rays Open

M Axelsson, M Ajello, M. Arimoto, L Baldini, J. Ballet , et al. · 2025

We present a complete analysis of Fermi Large Area Telescope (LAT) data of GRB 221009A, the brightest gamma-ray burst (GRB) ever detected. The burst emission above 30 MeV detected by the LAT preceded, by 1 s, the low-energy (<10 MeV) pulse…

Fermi detection of gamma-ray Emission from the Hot Coronae of Radio-quiet Active Galactic Nuclei Open

S. Abdollahi, M Ajello, Rafael Alves Batista, L Baldini, C. Bartolini , et al. · 2025

Relativistic jets around supermassive black holes (SMBHs) are well-known powerful $γ$-ray emitters. In absence of the jets in radio-quiet active galactic nuclei (AGNs), how the SMBHs work in $γ$-ray bands is still unknown despite of great …

Jetted subgalactic-size radio sources in merging galaxies Open

C. Stanghellini, M. Orienti, Cristiana Spingola, A. Zanichelli, D. Dallacasa , et al. · 2025

Context. The long-standing question concerning jetted subgalactic-size (JSS) radio sources is whether they will evolve into large radio galaxies, die before escaping the host galaxy, or remain indefinitely confined to their compact size. A…

Periodic Gamma-Ray Modulation of the Blazar PG 1553+113 Confirmed by Fermi-LAT and Multiwavelength Observations Open

S. Abdollahi, L. Baldini, G. Barbiellini, R. Bellazzini, B. Berenji , et al. · 2024

A 2.1 yr periodic oscillation of the gamma-ray flux from the blazar PG 1553+113 has previously been tentatively identified in ∼7 yr of data from the Fermi Large Area Telescope. After 15 yr of Fermi sky-survey observations, doubling the tot…

Search for Extended GeV Sources in the Inner Galactic Plane Open

S. Abdollahi, F. Acero, Amit Acharyya, Alessandro Adelfio, M. Ajello , et al. · 2024

The recent detection of extended $γ$-ray emission around middle-aged pulsars is interpreted as inverse-Compton scattering of ambient photons by electron-positron pairs escaping the pulsar wind nebula, which are confined near the system by …

Jetted subgalactic-size radio sources in merging galaxies -- A jet redirection scenario Open

C. Stanghellini, M. Orienti, Cristiana Spingola, A. Zanichelli, D. Dallacasa , et al. · 2024

Context: The long-standing question concerning jetted subgalactic-size (JSS) radio sources is whether they will evolve into large radio galaxies, die before escaping the host galaxy, or remain indefinitely confined to their compact size. A…

A high-resolution radio morphology and polarization of the kiloparsec-scale X-ray jet of PKS 1127−145 Open

M. Orienti, Aneta Siemiginowska, F. D'Ammando, Giulia Migliori · 2024

We report on new multifrequency Very Large Array (VLA) radio observations and Chandra X-ray observations of a radio-loud quasar with a ∼300 kpc-long jet, PKS 1127−145, during a flaring event detected in γ -rays by the Fermi Large Area Tele…

Investigating X-ray emission in the GeV-emitting compact symmetric objects PKS 1718–649 and TXS 1146+596 Open

E. Bronzini, Giulia Migliori, C. Vignali, M. Sobolewska, Ł. Stawarz , et al. · 2024

Aims. Compact symmetric objects (CSOs) are thought to represent the first step in the evolutionary path of radio galaxies. In the present study, we investigated the X-ray emission of two CSOs confirmed to emit at GeV energies: PKS 1718–649…

Investigating X-ray Emission in the GeV-emitting Compact Symmetric Objects PKS 1718-649 and TXS 1146+596 Open

E. Bronzini, Giulia Migliori, C. Vignali, M. Sobolewska, Ł. Stawarz , et al. · 2024

Compact Symmetric Objects (CSOs) are thought to represent the first step in the evolutionary path of radio galaxies. In this work, we investigate the X-ray emission of two CSOs confirmed to emit at GeV energies: PKS 1718-649 and TXS 1146+5…

Cold gas in the heart of Perseus A Open

R. Morganti, Suma Murthy, Tom Oosterloo, J. Blanchard, C. W. Cook , et al. · 2023

We present new JVLA and VLBA observations tracing the HI in the central region of 3C84 (Perseus A). This radio source is hosted by the bright cluster galaxy NGC 1275 in the centre of the iconic Perseus cluster. With the JVLA, we detected b…

Cold gas in the heart of Perseus A Open

R. Morganti, Suma Murthy, Tom Oosterloo, J. Blanchard, C. Cook , et al. · 2023

We present new Karl G. Jansky Very Large Array (JVLA) and Very Long Baseline Array (VLBA) observations that traced the H I in the central region of 3C 84 (Perseus A). This radio source is hosted by the bright cluster galaxy NGC 1275 in the…

RadioAstron Space VLBI Imaging of the Jet in M87. I. Detection of High Brightness Temperature at 22 GHz Open

Jae-Young Kim, T. Savolainen, P. A. Voitsik, Е. В. Кравченко, Mikhail Lisakov , et al. · 2023

We present results from the first 22 GHz space very long baseline interferometric (VLBI) imaging observations of M87 by RadioAstron. As a part of the Nearby AGN Key Science Program, the source was observed in 2014 February at 22 GHz with 2…

Probing the Heart of Active Narrow-line Seyfert 1 Galaxies with VERA Wideband Polarimetry Open

Mieko Takamura, Kazuhiro Hada, Mareki Honma, Tomoaki Oyama, Aya Yamauchi , et al. · 2023

We explored the parsec-scale nuclear regions of a sample of radio-loud narrow-line Seyfert 1 galaxies (NLSy1s) using the VLBI Exploration of Radio Astrometry wideband (at a recording rate of 16 Gbps) polarimetry at 22 and 43 GHz. Our targe…

Probing the Heart of Active Narrow-line Seyfert 1 Galaxies with VERA Wideband Polarimetry Open

Mieko Takamura, Kazuhiro Hada, Mareki Honma, Tomoaki Oyama, Aya Yamauchi , et al. · 2023

We explored the parsec-scale nuclear regions of a sample of radio-loud narrow-line Seyfert 1 galaxies (NLSy1s) using the VLBI Exploration of Radio Astronomy (VERA) wideband (at a recording rate of $16\,\mathrm{Gbps}$) polarimetry at 22 and…

Young but fading radio sources: searching for remnants among compact steep-spectrum radio sources Open

M. Orienti, M. Murgia, D. Dallacasa, Giulia Migliori, F. D’Ammando · 2023

The incidence of young but fading radio sources provides important information on the life cycle of radio emission in radio-loud active galactic nuclei. Despite its importance for constraining the models of radio source evolution, there ar…

Young but fading radio sources: searching for remnants among compact steep-spectrum radio sources Open

M. Orienti, M. Murgia, D. Dallacasa, Giulia Migliori, F. D'Ammando · 2023

The incidence of young but fading radio sources provides important information on the life cycle of radio emission in radio-loud active galactic nuclei. Despite its importance for constraining the models of radio source evolution, there ar…

RadioAstron Space VLBI Imaging of the jet in M87: I. Detection of high brightness temperature at 22 GHz Open

Jae-Young Kim, T. Savolainen, P. A. Voitsik, Е. В. Кравченко, Mikhail Lisakov , et al. · 2023

We present results from the first 22 GHz space very-long-baseline interferometric (VLBI) imaging observations of M87 by RadioAstron. As a part of the Nearby AGN Key Science Program, the source was observed in Feb 2014 at 22 GHz with 21 gro…

The Past and Future of East Asia to Italy: Nearly Global VLBI Open

G. Giovannini, Yuzhu Cui, Kazuhiro Hada, Kunwoo Yi, Hyunwook Ro , et al. · 2023

We present here the East Asia to Italy Nearly Global VLBI (EATING VLBI) project. How this project started and the evolution of the international collaboration between Korean, Japanese, and Italian researchers to study compact sources with …

The Past and Future of East Asia to Italy: Nearly Global VLBI Open

G. Giovannini, Yuzhu Cui, Kazuhiro Hada, Kunwoo Yi, Hyunwook Ro , et al. · 2023

We present here the East Asia to Italy Nearly Global VLBI (EATING VLBI) project. How this project started and the evolution of the international collaboration between Korean, Japanese, and Italian researchers to study compact sources with …

A VLBI investigation of high-energy neutrino emitter candidates Open

C. Nanci, M. Giroletti, M. Orienti, Giulia Migliori, J. Moldòn , et al. · 2023

High angular resolution observations with the very long baseline interferometry (VLBI) provide crucial tests for the association of neutrinos with blazars. The VLBI follow-up observations have led to the unveiling of VLBI-scales properties…

The Fourth Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope: Data Release 3 Open

M. Ajello, L. Baldini, J. Ballet, D. Bastieri, J. Becerra González , et al. · 2022

An incremental version of the fourth catalog of active galactic nuclei (AGNs) detected by the Fermi Large Area Telescope is presented. This version (4LAC-DR3) derives from the third data release of the 4FGL catalog based on 12 yr of E > 50…

The Fourth Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope -- Data Release 3 Open

The Fermi-LAT collaboration, NULL AUTHOR_ID, M. Ajello, L. Baldini, J. Ballet , et al. · 2022

An incremental version of the fourth catalog of active galactic nuclei (AGNs) detected by the Fermi-Large Area Telescope is presented. This version (4LAC-DR3) derives from the third data release of the 4FGL catalog based on 12 years of E>5…

Search for New Cosmic-Ray Acceleration Sites within the 4FGL Catalog Galactic Plane Sources Open

S. Abdollahi, F. Acero, M. Ackermann, L. Baldini, J. Ballet , et al. · 2022

Cosmic rays are mostly composed of protons accelerated to relativistic speeds. When those protons encounter interstellar material, they produce neutral pions, which in turn decay into gamma-rays. This offers a compelling way to identify th…

Incremental Fermi Large Area Telescope Fourth Source Catalog Open

S. Abdollahi, F. Acero, L. Baldini, J. Ballet, D. Bastieri , et al. · 2022

We present an incremental version (4FGL-DR3, for Data Release 3) of the fourth Fermi Large Area Telescope (LAT) catalog of γ -ray sources. Based on the first 12 years of science data in the energy range from 50 MeV to 1 TeV, it contains 66…

Multiwavelength View of the Close-by GRB 190829A Sheds Light on Gamma-Ray Burst Physics Open

O. S. Salafia, M. E. Ravasio, Jun Yang, Tao An, M. Orienti , et al. · 2022

We monitored the position of the close-by (about 370 Mpc) gamma-ray burst GRB 190829A, which originated from a massive star collapse, through very long baseline interferometry (VLBI) observations with the European VLBI Network and the Very…

Observing the inner parsec-scale region of candidate neutrino-emitting blazars Open

C. Nanci, M. Giroletti, M. Orienti, Giulia Migliori, A. Moralejo , et al. · 2022

Context. Many questions concerning the nature of astrophysical counterparts of high-energy neutrinos remain unanswered. There is increasing evidence of a connection between blazar jets and neutrino events, with the flare of the γ -ray blaz…

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