Publications (59)
Measurement of the photosphere oblateness of Cassiopeiae via Stellar Intensity Interferometry with the VERITAS Observatory
A. Archer, J. P. Aufdenberg, P. Bangale +58
We use the stellar intensity interferometry system implemented with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) at Fred Lawrence Whipple Observatory (FLWO…
The First Fermi-LAT Solar Flare Catalog
M. Ajello, L. Baldini, D. Bastieri +82
We present the first Fermi - Large Area Telescope (LAT) solar flare catalog covering the 24 th solar cycle. This catalog contains 45 Fermi -LAT solar flares (FLSFs) with emission i…
High-energy neutrino emission from the Milky Way
R. Abbasi, M. Ackermann, J. Adams +440
The Milky Way hosts astrophysical objects that accelerate cosmic rays to energies beyond the reach of terrestrial particle accelerators. It remains a longstanding goal to locate th…
Characterization of the Three-Flavor Composition of Cosmic Neutrinos with IceCube
R. Abbasi, M. Ackermann, J. Adams +429
Neutrinos oscillate over cosmic distances. Using 11.4 years of IceCube data, the flavor composition of the all-sky neutrino flux from 5\,TeV--10\,PeV is studied. We report the firs…
Multiwavelength variability and correlation studies of Mrk 421 during historically low X-ray and -ray activity in 20152016
MAGIC Collaboration, V. A. Acciari, S. Ansoldi +224
We report a characterization of the multi-band flux variability and correlations of the nearby (z=0.031) blazar Markarian 421 (Mrk 421) using data from Metsähovi, Swift, Fermi-LAT…
Broadband Multi-wavelength Properties of M87 during the 2018 EHT Campaign including a Very High Energy Flaring Episode
J. C. Algaba, M. Balokovic, S. Chandra +738
The nearby elliptical galaxy M87 contains one of the only two supermassive black holes whose emission surrounding the event horizon has been imaged by the Event Horizon Telescope (…
VERITAS Observations Contemporaneous with the LHAASO Detection of NGC 4278
The VERITAS Collaboration, A. Archer, P. Bangale +66
Significant gamma-ray emission between 1 TeV and 20 TeV from a point source, 1LHAASO J1219+2915, consistent with the location of the LINER/LLAGN galaxy NGC 4278 was recently report…
Optimal energy collection with rotational movements constraints in concentrated solar power plants
J. M. DÃaz-Bañez, J. M. Higes-López, M. A. Pérez-Cutiño +1
In Concentrated Solar Power (CSP) plants based on Parabolic Trough Collectors (PTC), the Sun is tracked at discrete time intervals, with each interval representing a movement of th…
GRB 221009A: the B.O.A.T Burst that Shines in Gamma Rays
M. Axelsson, M. Ajello, M. Arimoto +151
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…
Identification and Denoising of Radio Signals from Cosmic-Ray Air Showers using Convolutional Neural Networks
R. Abbasi, M. Ackermann, J. Adams +426
Radio pulses generated by cosmic-ray air showers can be used to reconstruct key properties like the energy and depth of the electromagnetic component of cosmic-ray air showers. Rad…
The Fermi-LAT Light Curve Repository
S. Abdollahi, M. Ajello, L. Baldini +110
The Fermi Large Area Telescope (LAT) light curve repository (LCR) is a publicly available, continually updated library of gamma-ray light curves of variable Fermi-LAT sources gener…
High-Energy Neutrino Tomography of the Earth's Interior with IceCube
The IceCube Collaboration, R. Abbasi, M. Ackermann +417
The Earth's interior reflects its geological evolution, from accretion to present-day dynamics. Its structure drives the geodynamo in the outer core, generating the magnetic field…
The exceptional 2017 gamma-ray flare of the radio galaxy NGC 1275: VERITAS and Multiwavelength Observations
A. Acharyya, A. Archer, P. Bangale +66
The radio galaxy NGC 1275 is the Brightest Cluster Galaxy in the Perseus cluster. It is well-studied across all wavebands, including Very High Energy (VHE; E>100GeV gamma-rays, and…
Fermi Large Area Telescope Performance After 10 Years Of Operation
The Fermi LAT Collaboration, M. Ajello, W. B. Atwood +126
The Large Area Telescope (LAT), the primary instrument for the Fermi Gamma-ray Space Telescope (Fermi) mission, is an imaging, wide field-of-view, high-energy gamma-ray telescope,…
IceCube Second Track Data Release IceTracks-DR2: Data from 2008-2022 for Neutrino Source Searches
R. Abbasi, M. Ackermann, J. Adams +412
We present IceCube's latest release of muon track data for neutrino point-source searches, extending the previously published 10-year dataset to cover 14 years of observations (Apr…
Deep Search for Joint Sources of Gravitational Waves and High-Energy Neutrinos with IceCube During the Third Observing Run of LIGO and Virgo
The IceCube Collaboration, R. Abbasi, M. Ackermann +2209
The discovery of joint sources of high-energy neutrinos and gravitational waves has been a primary target for the LIGO, Virgo, KAGRA, and IceCube observatories. The joint detection…
All-sky neutrino point-source search with IceCube combined track and cascade data
R. Abbasi, M. Ackermann, J. Adams +424
Despite extensive efforts, discovery of high-energy astrophysical neutrino sources remains elusive. We present an event-level simultaneous maximum likelihood analysis of tracks and…
Periodic Gamma-ray Modulation of the blazar PG 1553+113 Confirmed by Fermi-LAT and Multi-wavelength Observations
S. Abdollahi, L. Baldini, G. Barbiellini +98
A 2.1-year periodic oscillation of the gamma-ray flux from the blazar PG 1553+113 has previously been tentatively identified in almost 7 year of data from the Fermi Large Area Tele…
The IceCube-Gen2 Collaboration -- Contributions to the 39th International Cosmic Ray Conference (ICRC2025)
R. Abbasi, M. Ackermann, J. Adams +465
IceCube-Gen2 is a planned next-generation neutrino observatory at the South Pole that builds upon the successful design of IceCube. Integrating two complementary detection technolo…
Neural posterior estimation of the neutrino direction in IceCube using transformer-encoded normalizing flows on the sphere
R. Abbasi, M. Ackermann, J. Adams +411
IceCube is a cubic-kilometer-scale neutrino detector located at the geographic South Pole. A precise directional reconstruction of IceCube neutrinos is vital for associations with…
A Search for Millimeter-Bright Blazars as Astrophysical Neutrino Sources
R. Abbasi, M. Ackermann, J. Adams +424
The powerful jets of blazars have been historically considered as likely sites of high-energy cosmic-ray acceleration. However, particulars of the launched jet and the locations of…
Prompt Searches for Very-High-Energy γ-Ray Counterparts to IceCube Astrophysical Neutrino Alerts
J. Abhir, A. Biland, K. Brand +817
The search for sources of high-energy astrophysical neutrinos can be significantly advanced through a multi-messenger approach, which seeks to detect the gamma rays that accompany…
MAGIC and Fermi-LAT gamma-ray results on unassociated HAWC sources
M. L. Ahnen, S. Ansoldi, L. A. Antonelli +336
The HAWC Collaboration released the 2HWC catalog of TeV sources, in which 19 show no association with any known high-energy (HE; E > 10 GeV) or very-high-energy (VHE; E > 300 GeV)…
Exploring the nature of Galactic unassociated sources detected by the Fermi-LAT
F. Acero, A. Acharyya, A. Adelfio +120
We investigate the nature of the unassociated sources detected by the Fermi-LAT close (|b|<10°) to the Galactic plane, representing 16% of all sources in the 4FGL-DR4 catalog. The…
Constraints on Axion-Like Particles from VERITAS Observations of a Flaring Radio Galaxy in the Perseus Cluster
C. B. Adams, A. Archer, P. Bangale +62
Background: Axion-like particles (ALPs) are hypothetical particles that emerge in numerous theoretical extensions to the Standard Model. Their coupling to electromagnetic field imp…
Measurement of the mean number of muons with energies above 500 GeV in air showers detected with the IceCube Neutrino Observatory
R. Abbasi, M. Ackermann, J. Adams +413
We present a measurement of the mean number of muons with energies larger than 500 GeV in near-vertical extensive air showers initiated by cosmic rays with primary energies between…
Reducing the gap between general purpose data and aerial images in concentrated solar power plants
M. A. Pérez-Cutiño, J. Valverde, J. Capitán +1
In the context of Concentrated Solar Power (CSP) plants, aerial images captured by drones present a unique set of challenges. Unlike urban or natural landscapes commonly found in e…
Constraints on the Correlation of IceCube Neutrinos with Tracers of Large-Scale Structure
R. Abbasi, M. Ackermann, J. Adams +430
The IceCube Neutrino Observatory has observed extragalactic astrophysical neutrinos with an apparently isotropic distribution. Only a small fraction of the observed astrophysical n…
Search for new cosmic-ray acceleration sites within the 4FGL catalog Galactic plane sources
LAT Collaboration, S. Abdollahi, F. Acero +117
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 in…
Magnetically-induced buckling of a whirling conducting rod with applications to electrodynamic space tethers
J. Valverde, G. H. M. van der Heijden
We study the effect of a magnetic field on the behaviour of a slender conducting elastic structure, motivated by stability problems of electrodynamic space tethers. Both statical (…
HAWC, VERITAS, Fermi-LAT and XMM-Newton follow-up observations of the unidentified ultra-high-energy gamma-ray source LHAASO J2108+5157
The VERITAS collaboration, C. B. Adams, P. Bangale +142
We report observations of the ultra-high-energy gamma-ray source LHAASO J21085157, utilizing VERITAS, HAWC, Fermi-LAT, and XMM-Newton. VERITAS has collected 40 hours of d…
Improved measurements of the TeV-PeV extragalactic neutrino spectrum from joint analyses of IceCube tracks and cascades
R. Abbasi, M. Ackermann, J. Adams +424
The IceCube South Pole Neutrino Observatory has discovered the presence of a diffuse astrophysical neutrino flux at energies of TeV and beyond using neutrino induced muon tracks an…
A Gamma-ray Pulsar Timing Array Constrains the Nanohertz Gravitational Wave Background
M. Ajello, W. B. Atwood, L. Baldini +129
After large galaxies merge, their central supermassive black holes are expected to form binary systems whose orbital motion generates a gravitational wave background (GWB) at nanoh…
Evidence for a Spectral Break or Curvature in the Spectrum of Astrophysical Neutrinos from 5 TeV--10 PeV
R. Abbasi, M. Ackermann, J. Adams +424
We report improved measurements of the all flavor astrophysical neutrino spectrum with IceCube by combining complementary neutrino samples in two independent analyses. Both analyse…
Sensitivity Projections for Low-Mass Dark Matter Annihilation with the IceCube Upgrade
R. Abbasi, M. Ackermann, J. Adams +412
The IceCube Upgrade, an extension designed to enhance the IceCube Neutrino Observatory's detection of neutrinos with energies between 1 GeV and 500 GeV, will markedly improve IceCu…
VERITAS contributions to the 39th International Cosmic Ray Conference
A. Archer, P. Bangale, J. T. Bartkoske +55
Compilation of papers presented by the VERITAS Collaboration at the 39th International Cosmic Ray Conference (ICRC), held July 14 through July 24, 2025 in Geneva, Switzerland.
Evidence for neutrino emission from X-ray Bright Seyfert Galaxies in the Southern Hemisphere using Enhanced Starting Track Events with IceCube
R. Abbasi, M. Ackermann, J. Adams +428
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…
WavePID: Low-energy flavor identification using single-PMT time series in IceCube
R. Abbasi, M. Ackermann, J. Adams +416
The IceCube Neutrino Observatory, a cubic-kilometer detector at the South Pole, identifies neutrino flavor through event morphology. Sparse photon detection makes this classificati…
Unusual Isotopic Abundances in a Fully-Convective Stellar Binary
I. J. M. Crossfield, J. D. Lothringer, B. Flores +6
Low-mass M dwarfs represent the most common outcome of star formation, but their complex emergent spectra hinder detailed studies of their composition and initial formation. The me…
VERITAS and Fermi-LAT observations of new HAWC sources
VERITAS Collaboration, A. U. Abeysekara, A. Archer +280
The HAWC (High Altitude Water Cherenkov) collaboration recently published their 2HWC catalog, listing 39 very high energy (VHE; >100~GeV) gamma-ray sources based on 507 days of obs…
The IceCube Collaboration -- Contributions to the 39th International Cosmic Ray Conference (ICRC2025)
R. Abbasi, M. Ackermann, J. Adams +426
The IceCube Observatory at the South Pole has been operating in its full configuration since May 2011 with a duty cycle of about 99%. Its main component consists of a cubic-kilomet…
Search for GeV-scale Dark Matter from the Galactic Center with IceCube-DeepCore
The IceCube Collaboration, R. Abbasi, M. Ackermann +431
Models describing dark matter as a novel particle often predict that its annihilation or decay into Standard Model particles could produce a detectable neutrino flux in regions of…
Puzzling Variation of Gamma Rays from the Sun over the Solar Cycle Revealed with Fermi-LAT
A. Acharyya, A. Adelfio, M. Ajello +100
The steady-state gamma-ray emission from the Sun is thought to consist of two emission components due to interactions with Galactic cosmic rays: (1) a hadronic disk component, and…
Probing neutrino emission at GeV energies from compact binary mergers with the IceCube Neutrino Observatory
IceCube Collaboration, R. Abbasi, M. Ackermann +415
The advent of multi-messenger astronomy has allowed for new types of source searches by neutrino detectors. We present the results of the search for 0.5-100 GeV astrophysical neutr…
Search for Extended GeV Sources in the Inner Galactic Plane
S. Abdollahi, F. Acero, A. Acharyya +108
The recent detection of extended -ray emission around middle-aged pulsars is interpreted as inverse-Compton scattering of ambient photons by electron-positron pairs escaping th…
The High Energy X-ray Probe (HEX-P): Magnetars and Other Isolated Neutron Stars
J. A. J. Alford, G. A. Younes, Z. Wadiasingh +23
The hard X-ray emission from magnetars and other isolated neutron stars remains under-explored. An instrument with higher sensitivity to hard X-rays is critical to understanding th…
Helical buckling of a whirling conducting rod in a uniform magnetic field
J. Valverde, G. H. M. van der Heijden
We study the effect of a magnetic field on the behaviour of a conducting elastic rod subject to a novel set of boundary conditions that, in the case of a transversely isotropic rod…
Variability and Spectral Characteristics of Three Flaring Gamma-ray Quasars Observed by VERITAS and Fermi-LAT
C. B. Adams, J. Batshoun, W. Benbow +63
Flat spectrum radio quasars (FSRQs) are the most luminous blazars at GeV energies, but only rarely emit detectable fluxes of TeV gamma rays, typically during bright GeV flares. We…
The LED calibration systems for the mDOM and D-Egg sensor modules of the IceCube Upgrade
R. Abbasi, M. Ackermann, J. Adams +432
The IceCube Neutrino Observatory, instrumenting about 1 km of deep, glacial ice at the geographic South Pole, is due to be enhanced with the IceCube Upgrade. The IceCube Upgrad…
Limits on GeV-scale WIMP Annihilation in Dwarf Spheroidals with IceCube DeepCore
R. Abbasi, M. Ackermann, J. Adams +428
Dark matter is approximately five times more abundant than baryonic matter in the universe, but its physical nature continues to elude physicists. One potential candidate for dark…
Fermi and Swift Observations of GRB 190114C: Tracing the Evolution of High-Energy Emission from Prompt to Afterglow
M. Ajello, M. Arimoto, M. Axelsson +147
We report on the observations of gamma-ray burst (GRB) 190114C by the Fermi Gamma-ray Space Telescope and the Neil Gehrels Swift Observatory. The early-time observations reveal mul…
Fermi-GBM Discovery of GRB 221009A: An Extraordinarily Bright GRB from Onset to Afterglow
S. Lesage, P. Veres, M. S. Briggs +136
We report the discovery of GRB 221009A, the highest flux gamma-ray burst ever observed by the Fermi Gamma-ray Burst Monitor (GBM). This GRB has continuous prompt emission lasting m…
Limiting the Parameter Space for Unstable eV-scale Neutrinos Using IceCube Data
R. Abbasi, M. Ackermann, J. Adams +422
This Letter extends a recent IceCube sterile neutrino search to include unstable sterile neutrinos within the context of a model termed 3+1+Decay, which expands upon the 3+1 model…
Constraining the Prompt Atmospheric Neutrino Flux Combining IceCube's Cascade and Track Samples
R. Abbasi, M. Ackermann, J. Adams +428
The IceCube Neutrino Observatory has observed a diffuse flux of high-energy astrophysical neutrinos for more than a decade. A relevant background to the astrophysical flux is promp…
Probing a cosmogenic origin of astrophysical neutrinos and cosmic rays using gamma-ray observations of TXS 0506+056
A. Acharyya, A. Archer, P. Bangale +58
In September 2017, a high-energy neutrino event detected by the IceCube Neutrino Observatory (IceCube-170922A) was associated, at the level, with a gamma-ray flare from the b…
Search for High-Energy Neutrinos From the Sun Using Ten Years of IceCube Data
R. Abbasi, M. Ackermann, J. Adams +424
In this Letter, we present the results of a search for high-energy neutrinos produced by the annihilation of dark matter particles trapped in the Sun. Using 9.3 and 10.4 years of d…
IceCube Real-time Searches for High-energy Neutrinos Coincident with LIGO/Virgo/KAGRA Gravitational-Wave Alerts in O4a
The IceCube Collaboration, R. Abbasi, M. Ackermann +418
Gravitational-wave events from mergers of compact objects are a predicted source of high-energy neutrinos. Using data from the IceCube Neutrino Observatory, we search for neutrinos…
Multiwavelength observation of a candidate pulsar halo LHAASO J0621+3755 and the first X-ray detection of PSR J0622+3749
C. B. Adams, A. Archer, P. Bangale +71
Pulsar halos are regions around middle-aged pulsars extending out to tens of parsecs. The large extent of the halos and well-defined central cosmic-ray accelerators make this new c…
Evidence for Neutrino Emission from X-Ray-bright Active Galactic Nuclei with IceCube
R. Abbasi, M. Ackermann, J. Adams +429
Recently, IceCube reported neutrino emission from the Seyfert galaxy NGC 1068. Using 13.1 years of IceCube data, we present a follow-up search for neutrino sources in the northern…