W. Hanlon
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View article: Searching for EeV photons with Telescope Array Surface Detector and neural networks
Searching for EeV photons with Telescope Array Surface Detector and neural networks Open
Ultra-high-energy photons play an important role in probing astrophysical models and beyond-Standard-Model scenarios. We report updated limits on the diffuse photon flux using Telescope Array's Surface Detector data collected over 14 years…
View article: HAWC, VERITAS, Fermi-LAT, and XMM-Newton Follow-up Observations of the Unidentified Ultra-high-energy Gamma-Ray Source LHAASO J2108+5157
HAWC, VERITAS, Fermi-LAT, and XMM-Newton Follow-up Observations of the Unidentified Ultra-high-energy Gamma-Ray Source LHAASO J2108+5157 Open
We report observations of the ultra-high-energy gamma-ray source LHAASO J2108+5157, utilizing VERITAS, HAWC, Fermi-LAT, and XMM-Newton. VERITAS has collected ∼40 hr of data that we used to set ULs to the emission above 200 GeV. The HAWC da…
View article: Study of air shower reconstruction with asymmetric lateral distribution function for TAx4 SD
Study of air shower reconstruction with asymmetric lateral distribution function for TAx4 SD Open
View article: Multiwavelength Study of HESS J0632+057: New Insights into Pulsar–Disk Interaction
Multiwavelength Study of HESS J0632+057: New Insights into Pulsar–Disk Interaction Open
We present an analysis of new multiwavelength observations of the TeV gamma-ray binary HESS J0632+057, conducted using SALT, Swift, NuSTAR, and VERITAS in 2023–2024. By combining these new data with archival observations, we confirm previo…
View article: Time‐Resolved Leader Spectra of Downward Terrestrial Gamma‐Ray Flashes Observed at the Telescope Array Surface Detector
Time‐Resolved Leader Spectra of Downward Terrestrial Gamma‐Ray Flashes Observed at the Telescope Array Surface Detector Open
The first time‐resolved leader spectra associated with a downward Terrestrial Gamma‐ray Flash (TGF) observed by the Telescope Array Surface Detector (TASD) were recently reported by Kieu et al. (2024, https://doi.org/10.1029/2024JD041720 )…
View article: Multi-wavelength Study of HESS J0632+057: New Insights into Pulsar-Disk Interaction
Multi-wavelength Study of HESS J0632+057: New Insights into Pulsar-Disk Interaction Open
We present an analysis of new multi-wavelength observations of the TeV gamma-ray binary HESS J0632+057, conducted using SALT, Swift, NuSTAR, and VERITAS in 2023--2024. By combining these new data with archival observations, we confirm prev…
View article: Multiwavelength Observation of a Candidate Pulsar Halo LHAASO J0621+3755 and the First X-Ray Detection of PSR J0622+3749
Multiwavelength Observation of a Candidate Pulsar Halo LHAASO J0621+3755 and the First X-Ray Detection of PSR J0622+3749 Open
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 class of Galactic sources an ideal laboratory for studying c…
View article: Constraints on the X-Ray and Very-high-energy Gamma-Ray Flux from Supernova Remnant W44
Constraints on the X-Ray and Very-high-energy Gamma-Ray Flux from Supernova Remnant W44 Open
Observations of GeV gamma-ray emission from the well-studied mixed-morphology supernova remnant (SNR) W44 by Fermi-Large Area Telescope and AGILE imply that it is a site of significant cosmic-ray acceleration. The spectral energy distribut…
View article: Constraints on the X-ray and Very High Energy $γ$-ray Flux from Supernova Remnant W44
Constraints on the X-ray and Very High Energy $γ$-ray Flux from Supernova Remnant W44 Open
Observations of GeV gamma-ray emission from the well-studied mixed-morphology supernova remnant (SNR) W44 by Fermi-LAT and AGILE imply that it is a site of significant cosmic ray acceleration. The spectral energy distribution (SED) derived…
View article: An In-depth Study of Gamma Rays from the Starburst Galaxy M82 with VERITAS
An In-depth Study of Gamma Rays from the Starburst Galaxy M82 with VERITAS Open
Assuming Galactic cosmic rays originate in supernovae and the winds of massive stars, starburst galaxies should produce very-high-energy (VHE; E > 100 GeV) gamma-ray emission via the interaction of their copious quantities of cosmic rays w…
View article: VERITAS and multiwavelength observations of the Blazar B3 2247+381 in response to an IceCube neutrino alert
VERITAS and multiwavelength observations of the Blazar B3 2247+381 in response to an IceCube neutrino alert Open
While the sources of the diffuse astrophysical neutrino flux detected by the IceCube Neutrino Observatory are still largely unknown, one of the promising methods used towards understanding this is investigating the potential temporal and s…
View article: An in-depth study of Gamma rays from the Starburst Galaxy M 82 with VERITAS
An in-depth study of Gamma rays from the Starburst Galaxy M 82 with VERITAS Open
Assuming Galactic cosmic rays originate in supernovae and the winds of massive stars, starburst galaxies should produce very-high-energy (VHE; E$>$100 GeV) gamma-ray emission via the interaction of their copious quantities of cosmic rays w…
View article: Measurement of the photosphere oblateness of $γ$ Cassiopeiae via Stellar Intensity Interferometry with the VERITAS Observatory
Measurement of the photosphere oblateness of $γ$ Cassiopeiae via Stellar Intensity Interferometry with the VERITAS Observatory Open
We use the stellar intensity interferometry system implemented with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) at Fred Lawrence Whipple Observatory (FLWO) as a light collector to obtain measurements of the rapid …
View article: Multiwavelength observation of a candidate pulsar halo LHAASO J0621+3755 and the first X-ray detection of PSR J0622+3749
Multiwavelength observation of a candidate pulsar halo LHAASO J0621+3755 and the first X-ray detection of PSR J0622+3749 Open
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 class of Galactic sources an ideal laboratory for studying c…
View article: Intermediate Fluence Downward Terrestrial Gamma Ray Flashes as Observed by the Telescope Array Surface Detector
Intermediate Fluence Downward Terrestrial Gamma Ray Flashes as Observed by the Telescope Array Surface Detector Open
On 11 September 2021, two small thunderstorms developed over the Telescope Array Surface Detector (TASD) that produced an unprecedented number of six downward terrestrial gamma ray flashes (TGFs) within one‐hour timeframe. The TGFs occurre…
View article: First Time‐Resolved Leader Spectra Associated With a Downward Terrestrial Gamma‐Ray Flash Detected at the Telescope Array Surface Detector
First Time‐Resolved Leader Spectra Associated With a Downward Terrestrial Gamma‐Ray Flash Detected at the Telescope Array Surface Detector Open
Optical emissions associated with Terrestrial Gamma ray Flashes (TGFs) have recently become important subjects in space‐based and ground‐based observations as they can help us understand how TGFs are produced during thunderstorms. In this …
View article: Multiwavelength Investigation of γ-Ray Source MGRO J1908+06 Emission Using Fermi-LAT, VERITAS and HAWC
Multiwavelength Investigation of γ-Ray Source MGRO J1908+06 Emission Using Fermi-LAT, VERITAS and HAWC Open
This paper investigates the origin of the γ -ray emission from MGRO J1908+06 in the GeV–TeV energy band. By analyzing the data collected by the Fermi Large Area Telescope, the Very Energetic Radiation Imaging Telescope Array System, and Hi…
View article: A Multiwavelength Study to Decipher the 2017 Flare of the Blazar OJ 287
A Multiwavelength Study to Decipher the 2017 Flare of the Blazar OJ 287 Open
In 2017 February, the blazar OJ 287 underwent a period of intense multiwavelength activity. It reached a new historic peak in the soft X-ray (0.3–10 keV) band, as measured by the Swift X-ray Telescope. This event coincides with a very-high…
View article: Indirect search for dark matter with a combined analysis of dwarf spheroidal galaxies from VERITAS
Indirect search for dark matter with a combined analysis of dwarf spheroidal galaxies from VERITAS Open
Understanding the nature and identity of dark matter is a key goal in the physics community. In the case that TeV-scale dark matter particles decay or annihilate into Standard Model particles, very-high-energy (VHE) gamma rays (greater tha…
View article: An indirect search for dark matter with a combined analysis of dwarf spheroidal galaxies from VERITAS
An indirect search for dark matter with a combined analysis of dwarf spheroidal galaxies from VERITAS Open
Understanding the nature and identity of dark matter is a key goal in the physics community. In the case that TeV-scale dark matter particles decay or annihilate into standard model particles, very-high-energy (VHE) gamma rays (greater tha…
View article: A multi-wavelength study to decipher the 2017 flare of the blazar OJ 287
A multi-wavelength study to decipher the 2017 flare of the blazar OJ 287 Open
In February 2017, the blazar OJ~287 underwent a period of intense multiwavelength activity. It reached a new historic peak in the soft X-ray (0.3-10 keV) band, as measured by Swift-XRT. This event coincides with a very-high-energy (VHE) $γ…
View article: Mass composition of ultra-high energy cosmic rays from distribution of their arrival directions with the Telescope Array
Mass composition of ultra-high energy cosmic rays from distribution of their arrival directions with the Telescope Array Open
We use a new method to estimate the injected mass composition of ultrahigh cosmic rays (UHECRs) at energies higher than 10 EeV. The method is based on comparison of the energy-dependent distribution of cosmic ray arrival directions as meas…
View article: Isotropy of cosmic rays beyond $10^{20}$ eV favors their heavy mass composition
Isotropy of cosmic rays beyond $10^{20}$ eV favors their heavy mass composition Open
We report an estimation of the injected mass composition of ultra-high energy cosmic rays (UHECRs) at energies higher than 10 EeV. The composition is inferred from an energy-dependent sky distribution of UHECR events observed by the Telesc…
View article: First Time-Resolved Leader Spectra associated with a Downward Terrestrial Gamma-Ray Flash detected at the Telescope Array Surface Detector
First Time-Resolved Leader Spectra associated with a Downward Terrestrial Gamma-Ray Flash detected at the Telescope Array Surface Detector Open
Optical emissions associated with Terrestrial Gamma-ray Flashes (TGFs) have recently become important subjects in space-based and ground-based observations since these emissions play crucial roles in understanding the generation of TGFs du…
View article: Observation of Declination Dependence in the Cosmic Ray Energy Spectrum
Observation of Declination Dependence in the Cosmic Ray Energy Spectrum Open
We report on an observation of the difference between northern and southern skies of the ultrahigh energy cosmic ray energy spectrum with a significance of ${\sim}8σ$. We use measurements from the two largest experiments$\unicode{x2014}$th…
View article: An Angular Diameter Measurement of β UMa via Stellar Intensity Interferometry with the VERITAS Observatory
An Angular Diameter Measurement of β UMa via Stellar Intensity Interferometry with the VERITAS Observatory Open
We use the Very Energetic Radiation Imaging telescope Array System (VERITAS) imaging air Cherenkov telescope array to obtain the first measured angular diameter of β UMa at visual wavelengths using stellar intensity interferometry (SII) an…
View article: An Angular Diameter Measurement of $β$ UMa via Stellar Intensity Interferometry with the VERITAS Observatory
An Angular Diameter Measurement of $β$ UMa via Stellar Intensity Interferometry with the VERITAS Observatory Open
We use the VERITAS imaging air Cherenkov Telescope (IACT) array to obtain the first measured angular diameter of $β$ UMa at visual wavelengths using stellar intensity interferometry (SII) and independently constrain the limb-darkened angul…
View article: A Multiwavelength Investigation of PSR J2229+6114 and its Pulsar Wind Nebula in the Radio, X-Ray, and Gamma-Ray Bands
A Multiwavelength Investigation of PSR J2229+6114 and its Pulsar Wind Nebula in the Radio, X-Ray, and Gamma-Ray Bands Open
G106.3+2.7, commonly considered to be a composite supernova remnant (SNR), is characterized by a boomerang-shaped pulsar wind nebula (PWN) and two distinct (“head” and “tail”) regions in the radio band. A discovery of very-high-energy gamm…
View article: A Multiwavelength Investigation of PSR J2229+6114 and its Pulsar Wind Nebula in the Radio, X-Ray, and Gamma-Ray Bands
A Multiwavelength Investigation of PSR J2229+6114 and its Pulsar Wind Nebula in the Radio, X-Ray, and Gamma-Ray Bands Open
G106.3+2.7, commonly considered to be a composite supernova remnant (SNR), is characterized by a boomerang-shaped pulsar wind nebula (PWN) and two distinct (“head” and “tail”) regions in the radio band. A discovery of very-high-energy gamm…
View article: VERITAS contributions to the 38th International Cosmic Ray Conference
VERITAS contributions to the 38th International Cosmic Ray Conference Open
Compilation of papers presented by the VERITAS Collaboration at the 38th International Cosmic Ray Conference (ICRC), held July 26 through August 3, 2023 in Nagoya, Japan.