arXiv subjects

Rene A. Ong

Publications and source records attributed to Rene A. Ong.

17 recordsLinked to original sources

arXiv2026

A Multiwavelength Study of a Long-Duration VHE Flare from BL Lacertae with VERITAS

We report the first observations of a long-duration very-high-energy (VHE; $E > 100$ GeV) flare from BL Lacertae (VER J2202+422), taken with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). On October 15, 2022, the Fermi-Large Area Telescope (LAT) detected elevated GeV activity originating from this blazar. This triggered a multiwavelength campaign, which includes observations from VERITAS, Swift, NuSTAR, and select optical and radio observatories. VERITAS observed the source for a total of $\sim 9.8$ hours between September 1, 2022 and December 1, 2022. An analysis of these data yields a $\sim 28 σ$ detection of the source. While previously observed VHE flares from BL Lacertae have lasted on time-scales of minutes to days, VERITAS continued to detect flaring activity from the source for over a month ($\sim 40$ days) after the original flaring activity was detected with Fermi-LAT. Broadband spectral modeling shows that a synchrotron self-Compton (SSC) model with an external inverse-Compton (EC) component is preferred over a one-zone SSC model.

astro-ph.HE↗

arXiv2026

The General Antiparticle Spectrometer (GAPS) Antarctic Balloon Payload

The General Antiparticle Spectrometer (GAPS) is an Antarctic stratospheric balloon mission designed to provide unmatched sensitivity to low-energy (<0.25 GeV/n) cosmic-ray antiprotons, antideuterons, and antihelium nuclei as signatures of dark matter. The distinctive GAPS particle identification technique relies on measuring the energy loss along the track of an incoming antinucleus as it slows down and is captured into an exotic atom, and then detecting the de-excitation X-rays and the nuclear annihilation products. This measurement is realized using a Tracker composed of more than 1000 custom silicon strip detectors and a plastic scintillator time-of-flight (TOF) system instrumenting more than 40m$^2$. Together, these subsystems provide the velocity and energy resolution, stopping power, particle tracking, and X-ray identification necessary to distinguish rare antinucleus signals from the abundant positive-nucleus backgrounds, all within the constraints of a high-altitude mission. A multi-loop capillary heat pipe system has been developed to maintain the tracker operating temperature with significant mass and power savings over a conventional pump-based system. The first GAPS science payload flew for 25 days during the 2025/26 NASA Antarctic balloon campaign. We detail the design, integration, and commissioning of the payload prior to flight.

astro-ph.IM↗

arXiv2025

VERITAS and multiwavelength observations of the Blazar B3 2247+381 in response to an IceCube neutrino alert

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 spatial correlations between neutrino alerts and the electromagnetic radiation from blazars. We report on the multiwavelength target-of-opportunity observations of the blazar B3 2247+381, taken in response to an IceCube multiplet alert for a cluster of muon neutrino events compatible with the source location between May 20, 2022 and November 10, 2022. B3 2247+381 was not detected with VERITAS during this time period. The source was found to be in a low-flux state in the optical, ultraviolet and gamma-ray bands for the time interval corresponding to the neutrino event, but was detected in the hard X-ray band with NuSTAR during this period. We find the multiwavelength spectral energy distribution is well described using a simple one-zone leptonic synchrotron self-Compton radiation model. Moreover, assuming the neutrinos originate from hadronic processes within the jet, the neutrino flux would be accompanied by a photon flux from the cascade emission, and the integrated photon flux required in such a case would significantly exceed the total multiwavelength fluxes and the VERITAS upper limits presented here. The lack of flaring activity observed with VERITAS, combined with the low multiwavelength flux levels, and given the significance of the neutrino excess is at 3$σ$ level (uncorrected for trials), makes B3 2247+381 an unlikely source of the IceCube multiplet. We conclude that the neutrino excess is likely a background fluctuation.

astro-ph.HE↗

arXiv2025

An in-depth study of Gamma rays from the Starburst Galaxy M 82 with VERITAS

Assuming Galactic cosmic rays originate in supernovae and the winds of massive stars, starburst galaxies should produce very-high-energy (VHE; E$>$100 GeV) gamma-ray emission via the interaction of their copious quantities of cosmic rays with the large reservoirs of dense gas within the galaxies. Such VHE emission was detected by VERITAS from the starburst galaxy M 82 in 2008-09. An extensive, multi-year campaign followed these initial observations, yielding a total of 254 h of good quality VERITAS data on M 82. Leveraging modern analysis techniques and the larger exposure, these VERITAS data show a more statistically significant VHE signal ($\sim$6.5 standard deviations ($σ$)). The corresponding photon spectrum is well fit by a power law ($Γ= 2.3 \pm 0.3_{stat} \pm0.2_{sys}$) and the observed integral flux is F($>$450 GeV) = $(3.2 \pm0.6_{stat} \pm 0.6_{sys}) \times 10^{-13}~\mathrm{cm^{-2}~s}^{-1}$, or $\sim$0.4\% of the Crab Nebula flux above the same energy threshold. The improved VERITAS measurements, when combined with various multi-wavelength data, enable modeling of the underlying emission and transport processes. A purely leptonic scenario is found to be a poor representation of the gamma-ray spectral energy distribution (SED). A lepto-hadronic scenario with cosmic rays following a power-law spectrum in momentum (index $s\simeq 2.25$), and with significant bremsstrahlung below $1$~GeV, provides a good match to the observed SED. The synchrotron emission from the secondary electrons indicates that efficient non-radiative losses of cosmic-ray electrons may be related to advective escape from the starburst core.

astro-ph.HE↗

arXiv2023

A VERITAS/Breakthrough Listen Search for Optical Technosignatures

The Breakthrough Listen Initiative is conducting a program using multiple telescopes around the world to search for "technosignatures": artificial transmitters of extraterrestrial origin from beyond our solar system. The VERITAS Collaboration joined this program in 2018, and provides the capability to search for one particular technosignature: optical pulses of a few nanoseconds duration detectable over interstellar distances. We report here on the analysis and results of dedicated VERITAS observations of Breakthrough Listen targets conducted in 2019 and 2020 and of archival VERITAS data collected since 2012. Thirty hours of dedicated observations of 136 targets and 249 archival observations of 140 targets were analyzed and did not reveal any signals consistent with a technosignature. The results are used to place limits on the fraction of stars hosting transmitting civilizations. We also discuss the minimum-pulse sensitivity of our observations and present VERITAS observations of CALIOP: a space-based pulsed laser onboard the CALIPSO satellite. The detection of these pulses with VERITAS, using the analysis techniques developed for our technosignature search, allows a test of our analysis efficiency and serves as an important proof-of-principle.

astro-ph.IM↗

arXiv2023

VERITAS discovery of very high energy gamma-ray emission from S3 1227+25 and multiwavelength observations

We report the detection of very high energy gamma-ray emission from the blazar S3 1227+25 (VER J1230+253) with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). VERITAS observations of the source were triggered by the detection of a hard-spectrum GeV flare on May 15, 2015 with the Fermi-Large Area Telescope (LAT). A combined five-hour VERITAS exposure on May 16th and May 18th resulted in a strong 13$σ$ detection with a differential photon spectral index, $Γ$ = 3.8 $\pm$ 0.4, and a flux level at 9% of the Crab Nebula above 120 GeV. This also triggered target of opportunity observations with Swift, optical photometry, polarimetry and radio measurements, also presented in this work, in addition to the VERITAS and Fermi-LAT data. A temporal analysis of the gamma-ray flux during this period finds evidence of a shortest variability timescale of $τ_{obs}$ = 6.2 $\pm$ 0.9 hours, indicating emission from compact regions within the jet, and the combined gamma-ray spectrum shows no strong evidence of a spectral cut-off. An investigation into correlations between the multiwavelength observations found evidence of optical and gamma-ray correlations, suggesting a single-zone model of emission. Finally, the multiwavelength spectral energy distribution is well described by a simple one-zone leptonic synchrotron self-Compton radiation model.

astro-ph.HE↗

arXiv2021

A Search for TeV Gamma-ray Emission from Pulsar Tails by VERITAS

We report on the search for very-high-energy gamma-ray emission from the regions around three nearby supersonic pulsars (PSR B0355+54, PSR J0357+3205 and PSR J1740+1000) that exhibit long X-ray tails. To date there is no clear detection of TeV emission from any pulsar tail that is prominent in X-ray or radio. We provide upper limits on the TeV flux, and luminosity, and also compare these limits with other pulsar wind nebulae detected in X-rays and the tail emission model predictions. We find that at least one of the three tails is likely to be detected in observations that are a factor of 2-3 more sensitive. The analysis presented here also has implications for deriving the properties of pulsar tails, for those pulsars whose tails could be detected in TeV.

astro-ph.HE↗

arXiv2013

Recent VERITAS Results on VHE Gamma-ray Sources in Cygnus

The Cygnus region of the Galactic plane is a promising target for high-energy and very high energy (VHE) gamma-ray telescopes as it is home to many potential sources, such as supernova remnants, pulsar wind nebulae, X-ray binaries and massive star clusters. The VHE gamma-ray observatory VERITAS (Very Energetic Radiation Imaging Telescope Array System) is an array of four 12 m diameter imaging atmospheric Cherenkov telescopes located at Mt. Hopkins, AZ, USA. Over the period of 2007 to 2012, VERITAS has carried out extensive observations in the direction of Cygnus. These observations were initiated by a sky survey that covered Galactic longitudes between 67 and 82 degrees and Galactic latitudes between -1 and 4 degrees. Additional deep observations have been made near specific sources, including TeV J2032+4130, Cygnus X-3, VER J2019+407 (SNR G78.2+2.1/gamma-Cygni), CTB 87, and MGRO J2019+37. This paper summarizes the latest VERITAS results on the various source detections in the direction of Cygnus and our current understanding of the origin for the VHE gamma-ray emission.

astro-ph.HE↗

arXiv2013

CF2 White Paper: Status and Prospects of The VERITAS Indirect Dark Matter Detection Program

In this white paper, submitted as a part of Snowmass 2013 (subgroup CF2), we examine the current status and future prospects of the VERITAS indirect dark matter detection program. The VERITAS array of imaging atmospheric Cherenkov telescopes (IACTs), sensitive in the 0.1-50 TeV regime, is in the process of completing a multi-year program aimed at detecting signatures of neutralino dark matter. This program is spread out over a range of astrophysical targets which can potentially yield definitive signatures of neutralino self-annihilation such as dwarf spheroidal galaxies (dSphs) and the center of the Milky Way galaxy. While the program is still in progress, initial results on dSphs have produced very competitive upper limits on the thermally averaged cross-section of neutralino self-annihilation as well as strongly constraining leptophillic dark matter models (such as those inferred from the PAMELA and AMS positron fraction results). As the program continues over the next 5 years, VERITAS observations will yield some of the strongest constraints available from IACTs, pushing down the limit on the thermally averaged cross-section of neutralino self-annihilation to the expected natural thermal relic scale.

astro-ph.HE↗

arXiv2013

Highlights from VERITAS on VHE Gamma-ray Sources in our Galaxy

VERITAS is a major ground-based detector of very high energy (VHE, E > 100 GeV) gamma rays and cosmic rays. VERITAS consists of an ar- ray of four 12m-diameter atmospheric Cherenkov telescopes that has been fully operational since September 2007. VERITAS has detected many as- trophysical sources of VHE gamma rays, including at least 17 VHE sources that are likely Galactic in origin. This paper describes some of the Galactic source highlights from VERITAS with an emphasis on those aspects that relate to the origin of cosmic rays. Specifically, topics include the VERITAS discovery of VHE emission from the Tycho and CTA 1 supernova remnants, the identification of HESS J0632+057 as a new VHE binary, a substantially improved view of the gamma-ray emission in the Cygnus OB1 region, and the recent remarkable discovery of VHE emission from the Crab pulsar. In 2009, VERITAS was upgraded by relocation of one of the telescopes, leading to a significant improvement in sensitivity. A program to further improve the performance of VERITAS, involving the upgrade of the telescope trigger systems and the telescope cameras, was completed in summer 2012. The upgrade will lead to an improved sensitivity and a lower energy threshold for VERITAS, allowing it to perform deeper observations of known Galactic and extragalactic sources and to detect fainter and more distant sources.

astro-ph.HE↗

arXiv2006

The Status of VHE Gamma-Ray Astronomy

This paper presents a summary of the status of the field of very high-energy (VHE) gamma-ray astronomy, as of early 2006. The paper is based on the Rapporteur Talk given at the 29th International Cosmic Ray Conference in Pune, India (ICRC 2005). It covers astrophysical results from observations made by high-energy and very high-energy telescopes operating at photon energies above 1 GeV. The majority of recent observations in this field have been made by ground-based telescopes using the atmospheric Cherenkov or air shower techniques.

astro-ph↗

arXiv2003

The Status of Very High Energy Astronomy

This paper summarizes the status of very high-energy (VHE) astronomy, as of early 2003. It concentrates on observations made by gamma-ray telescopes operating at energies above 10 GeV. This field is an exciting one to be working in, with a growing and varied list of established sources that includes plerions, supernova remnants, and active galactic nuclei. New results include the discovery of the first unidentified source at these energies and the detection of gamma rays from a nearby starburst galaxy (NGC 253). The arrival of a new generation of telescopes, both on the ground and in space, argues that we can anticipate a wealth of exciting results in the near future.

astro-ph↗

arXiv2003

The Veritas Project

VERITAS is a new, major ground-based gamma-ray observatory designed to significantly advance our understanding of extreme astrophysical processes in the universe. The observatory comprises seven large-aperture (12m diameter) Cherenkov telescopes, each equipped with an imaging camera. The first phase of VERITAS (consisting of four telescopes) is currently under construction. Here we outline the key features of VERITAS and provide an update on its status.

astro-ph↗

arXiv2000

High Energy Particles from the Universe

The field of high energy particle astronomy is exciting and rapidly developing. In the last few years, we have detected extragalactic sources of intense TeV gamma radiation and individual cosmic ray particles with energies exceeding 25 Joules. Understanding the workings of astrophysics under extreme conditions is the primary goal of this field. Also important is the possibility of using high energy particles from space to probe beyond the standard models of particle physics and cosmology. This paper presents a review of high energy particle astronomy using photons, cosmic rays, and neutrinos.

hep-ex↗

arXiv1997

The STACEE Project

The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) is a telescope designed to explore the gamma-ray sky between 20 and 250 GeV using the atmospheric Cherenkov technique. STACEE is currently under construction. When completed, it will use 48 large heliostat mirrors at the solar research facility at Sandia National Laboratories (Albuquerque, NM) to reflect Cherenkov light created in gamma-ray air showers to secondary mirrors on a central tower. The secondary mirrors image this light onto photomultiplier tube cameras. This paper provides an overview of the STACEE project, including a description of the experimental site and an outline of the current design for the detector components.

astro-ph↗

arXiv1997

Development of the Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE)

STACEE is a proposed atmospheric Cherenkov telescope for ground-based gamma-ray astrophysics between 25 and 500 GeV. The telescope will make use of the large solar mirrors (heliostats) available at a solar research facility to achieve an energy threshold lower than any existing ground-based instrument. This paper describes the development of STACEE, including an overview of the complete instrument design and a discussion of results from recent prototype tests at the large solar heliostat field of Sandia National Laboratories.

astro-ph↗

arXiv1996

Detection of Atmospheric Cherenkov Radiation Using Solar Heliostat Mirrors

The gamma-ray energy region between 20 and 250 GeV is largely unexplored. Ground-based atmospheric Cherenkov detectors offer a possible way to explore this region, but large Cherenkov photon collection areas are needed to achieve low energy thresholds. This paper discusses the development of a Cherenkov detector using the heliostat mirrors of a solar power plant as the primary collector. As part of this development, we built a prototype detector consisting of four heliostat mirrors and used it to record atmospheric Cherenkov radiation produced in extensive air showers created by cosmic ray particles.

astro-ph↗