A5047756698- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Dark Matter and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Particle Detector Development and Performance
- Astrophysical Phenomena and Observations
- Neutrino Physics Research
- Pulsars and Gravitational Waves Research
- Particle Accelerators and Free-Electron Lasers
- Astronomical Observations and Instrumentation
- Radiation Detection and Scintillator Technologies
- Particle physics theoretical and experimental studies
- Planetary Science and Exploration
- Cosmology and Gravitation Theories
- Gyrotron and Vacuum Electronics Research
- Astronomy and Astrophysical Research
- Photocathodes and Microchannel Plates
- Space Science and Extraterrestrial Life
- Stellar, planetary, and galactic studies
- Atmospheric Ozone and Climate
- Astro and Planetary Science
- Galaxies: Formation, Evolution, Phenomena
- Superconducting Materials and Applications
- Particle accelerators and beam dynamics
- Solar and Space Plasma Dynamics
University of California, Santa Cruz
2016-2024
Universidad Veritas
2020-2023
California State University, East Bay
2023
University of Delaware
2023
University of California, Berkeley
2023
Center for Astrophysics Harvard & Smithsonian
2023
Instituto de Astrofísica de Canarias
2021-2023
Universidad de La Laguna
2021-2023
University of California, San Diego
2023
Harvard University
2023
The inner region of the Milky Way halo harbors a large amount dark matter (DM). Given its proximity, it is one most promising targets to look for DM. We report on search annihilations DM particles using γ-ray observations towards 300 pc Way, with H.E.S.S. array ground-based Cherenkov telescopes. analysis based 2D maximum likelihood method Galactic Center (GC) data accumulated by over last 10 years (2004-2014), and does not show any significant signal above background. Assuming Einasto...
Axionlike particles (ALPs) are hypothetical light (sub-eV) bosons predicted in some extensions of the Standard Model particle physics. In astrophysical environments comprising high-energy gamma rays and turbulent magnetic fields, existence ALPs can modify energy spectrum for a sufficiently large coupling between photons. This modification would take form an irregular behavior limited range. Data from H.E.S.S. observations distant BL Lac object PKS 2155-304 (z = 0.116) used to derive upper...
Supernova remnants exhibit shock fronts (shells) that can accelerate charged particles up to very high energies. In the past decade, measurements of a handful shell-type supernova in very-high-energy gamma rays have provided unique insights into acceleration process. Among those objects, RX$~$J1713.7-3946 (also known as G347.3-0.5) has largest surface brightness, allowing us perform most comprehensive study morphology and spatially resolved spectra any such gamma-ray source. Here we present...
We present constraints on the annihilation cross section of weakly interacting massive particles dark matter based joint statistical analysis four dwarf galaxies with VERITAS. These results are derived from an optimized photon weighting technique that improves standard imaging atmospheric Cherenkov telescope (IACT) analyses by utilizing spectral and spatial properties individual events. report $\ensuremath{\sim}230$ hours observations five galaxies. find no evidence gamma-ray emission any...
Dwarf spheroidal galaxies of the Local Group are close satellites Milky Way characterized by a large mass-to-light ratio and not expected to be site non-thermal high-energy gamma-ray emission or intense star formation. Therefore they amongst most promising candidates for indirect dark matter searches. During last years High Energy Stereoscopic System (H.E.S.S.) imaging atmospheric Cherenkov telescopes observed five these dwarf more than 140 hours in total, searching TeV from annihilation...
Diffuse $\ensuremath{\gamma}$-ray emission is the most prominent observable signature of celestial cosmic-ray interactions at high energies. While already being investigated GeV energies over several decades, assessments diffuse TeV remain sparse. After completion systematic survey inner Galaxy, H.E.S.S. experiment in a prime position to observe large-scale Data Galactic Plane Survey are regions off known sources. Corresponding flux measurements were made an extensive grid locations....
The Galactic Center (GC) region hosts a variety of powerful astronomical sources and rare astrophysical processes that emit large flux non-thermal radiation. inner 375 pc x 600 region, called the Central Molecular Zone, is home to supermassive black hole Sagittarius A*, massive cloud complexes, particle accelerators such as supernova remnants. We present results our improved analysis very-high-energy (VHE) gamma-ray emission above 2 TeV from GC using 125 hours data taken with VERITAS...
Very high energy (VHE, E > 100 GeV) γ-ray flaring activity of the high-frequency peaked BL Lac object PG 1553+113 has been detected by H.E.S.S. telescopes. The flux source increased a factor 3 during nights 2012 April 26 and 27 with respect to archival measurements hint intra-night variability. No counterpart this event in Fermi-Large Area Telescope data. This pattern is consistent VHE being caused injection ultrarelativistic particles, emitting γ-rays at highest energies. dataset offers...
About 40% of the observation time High Energy Stereoscopic System (H.E.S.S.) is dedicated to studying active galactic nuclei (AGN), with aim increasing sample known extragalactic very-high-energy (VHE, E>100 GeV) sources and constraining physical processes at play in potential emitters. H.E.S.S. observations AGN, spanning a period from April 2004 December 2011, are investigated constrain their gamma-ray fluxes. Only 47 without significant excess detected position targets presented. Upper...
We report on observations of the pulsar / Be star binary system PSR J2032+4127 MT91 213 in energy range between 100 GeV and 20 TeV with VERITAS MAGIC imaging atmospheric Cherenkov telescope arrays. The orbit has a period approximately 50 years, most recent periastron occurring 2017 November 13. Our span from 18 months prior to one month after. A new, point-like, gamma-ray source is detected, coincident location 213. light curve spectrum are well-characterized over passage. flux variable at...
We present a search for magnetically broadened gamma-ray emission around active galactic nuclei (AGNs), using VERITAS observations of seven hard-spectrum blazars. A cascade process occurs when multi-TeV gamma-rays from an AGN interact with extragalactic background light (EBL) photons to produce electron–positron pairs, which then cosmic microwave via inverse-Compton scattering gamma-rays. Due the deflection non-zero intergalactic magnetic field (IGMF) would potentially detectable effects on...
Cosmic-ray electrons and positrons (CREs) at GeV-TeV energies are a unique probe of our local Galactic neighborhood. CREs lose energy rapidly via synchrotron radiation inverse-Compton scattering processes while propagating within the Galaxy, these losses limit their propagation distance. For with TeV energies, is on order kiloparsec. Within that distance, there only few known astrophysical objects capable accelerating to such high energies. It also possible products annihilation or decay...
A search for dark matter line-like signals was performed in the vicinity of Galactic Centre by H.E.S.S. experiment on observational data taken 2014. An unbinned likelihood analysis developed to improve sensitivity signals. The upgraded along with newer extend energy coverage previous measurement down 100 GeV. 18 h collected array allow one rule out at 95% CL presence a 130 GeV line (at $l = -1.5^{\circ}, b 0^{\circ}$ and profile centered this location) previously reported Fermi-LAT data....
We present results from deep observations towards the Cygnus region using 300 hours of very-high-energy (VHE) $\gamma$-ray data taken with VERITAS Cherenkov telescope array and over seven years high-energy Fermi satellite at an energy above 1 GeV. As brightest diffuse emission in northern sky, provides a promising area to probe origins cosmic rays. report identification potential Fermi-LAT counterpart VER J2031+415 (TeV J2032+4130), resolve extended VHE source J2019+368 into two candidates...
Blazars are usually classified following their synchrotron peak frequency ($νF(ν)$ scale) as high, intermediate, low peaked BL Lacs (HBLs, IBLs, LBLs), and flat spectrum radio quasars (FSRQs), or, according to morphology at large scale, FR~I or FR~II. However, the diversity of blazars is such that these classes seem insufficient chart specific properties each source. We propose classify a wide sample kinematic features jets seen in very long baseline interferometry (VLBI). For this purpose...
We present a study of $\gamma$-ray emission from the core-collapse supernova remnant Cas~A in energy range 0.1GeV to 10TeV. used 65 hours VERITAS data cover 200 GeV - 10 TeV, and 10.8 years \textit{Fermi}-LAT 0.1-500 GeV. The spectral analysis shows significant curvature around $1.3 \pm 0.4_{stat}$ that is consistent with expected spectrum pion decay. Above this energy, joint deviates significantly simple power-law, best described by power-law index $2.17\pm 0.02_{stat}$ cut-off $2.3...
Abstract Dark matter is a key piece of the current cosmological scenario, with weakly interacting massive particles (WIMPs) leading dark candidate. WIMPs have not been detected in their conventional parameter space (100 GeV ≲ M χ 100 TeV), mass range accessible Imaging Atmospheric Cherenkov Telescopes. As ultraheavy (UHDM; ≳ TeV) has suggested as an underexplored alternative to WIMP paradigm, we search for indirect annihilation signal higher (up 30 PeV) VERITAS γ -ray observatory. With 216...
An annihilation signal of dark matter is searched for from the central region Milky Way. Data acquired in dedicated on-off observations Galactic center with H.E.S.S. are analyzed this purpose. No significant found a total ∼9 h observations. Upper limits on velocity averaged cross section, ⟨σv⟩, particles masses range ∼300 GeV to ∼10 TeV derived. In contrast previous constraints derived region, that here apply also under assumption core constant density around Galaxy. Values ⟨σv⟩ larger than...
Context. On March 4, 2013, the Fermi-LAT and AGILE reported a flare from direction of Crab Nebula in which high-energy (HE; E > 100 MeV) flux was six times above its quiescent level. Simultaneous observations other energy bands give us hints about emission processes during episode physics pulsar wind nebulae general. Aims. We search for variability at very-high energies (VHE; GeV), using contemporaneous data taken with H.E.S.S. array Cherenkov telescopes. Methods. Observational instrument on...
Abstract On 2017 September 22, the IceCube Neutrino Observatory reported detection of high-energy neutrino event IC 170922A, potential astrophysical origin. It was soon determined that direction consistent with location gamma-ray blazar TXS 0506+056 (3FGL J0509.4+0541), which in an elevated emission state as measured by Fermi satellite. Very Energetic Radiation Imaging Telescope Array System (VERITAS) observations neutrino/blazar region started on 23 response to alert and continued through...
We report on variability and correlation studies using multiwavelength observations of the blazar Mrk 421 during month February, 2010 when an extraordinary flare reaching a level $\sim$27~Crab Units above 1~TeV was measured in very-high-energy (VHE) $\gamma$-rays with VERITAS observatory. This is highest flux state for ever observed VHE $\gamma$-rays. Data are analyzed from coordinated campaign across multiple instruments including $\gamma$-ray (VERITAS, MAGIC), high-energy (HE) (Fermi-LAT),...
While the sources of diffuse astrophysical neutrino flux detected by IceCube Neutrino Observatory are still largely unknown, one promising methods used towards understanding this is investigating potential temporal and spatial correlations between alerts electromagnetic radiation from blazars. We report on multiwavelength target-of-opportunity observations blazar B3 2247+381, taken in response to an multiplet alert for a cluster muon events compatible with source location May 20, 2022...
Abstract The large-scale universal structure comprises strands of dark matter and galaxies with large underdense volumes known as voids. We measure the fraction line sight that intersects voids for active galactic nuclei (AGN) detected by Fermi Large Area Telescope (LAT) quasars from Sloan Digital Sky Survey (SDSS). This “voidiness” is a rudimentary proxy density along to galaxies. voidiness SDSS-observed (QSOs) distinctly different randomly distributed source populations, median p -value...