Publications (76)
A survey of active galaxies at TeV photon energies with the HAWC gamma-ray observatory
A. Albert, C. Alvarez, J. R. Angeles Camacho +86
The High Altitude Water Cherenkov Gamma-Ray Observatory (HAWC) continuously detects TeV photons and particles within its large field-of-view, accumulating every day a deeper exposu…
Constraining the Ratio in TeV Cosmic Rays with Observations of the Moon Shadow by HAWC
A. U. Abeysekara, A. Albert, R. Alfaro +98
An indirect measurement of the antiproton flux in cosmic rays is possible as the particles undergo deflection by the geomagnetic field. This effect can be measured by studying the…
First NuSTAR Observations of Mrk 501 within a Radio to TeV Multi-Instrument Campaign
A. Furniss, K. Noda, S. Boggs +273
We report on simultaneous broadband observations of the TeV-emitting blazar Markarian 501 between 1 April and 10 August 2013, including the first detailed characterization of the s…
Very high energy particle acceleration powered by the jets of the microquasar SS 433
HAWC Collaboration, A. U. Abeysekara, A. Albert +104
SS 433 is a binary system containing a supergiant star that is overflowing its Roche lobe with matter accreting onto a compact object (either a black hole or neutron star). Two jet…
A search for spectral hysteresis and energy-dependent time lags from X-ray and TeV gamma-ray observations of Mrk 421
A. U. Abeysekara, S. Archambault, A. Archer +220
Blazars are variable emitters across all wavelengths over a wide range of timescales, from months down to minutes. It is therefore essential to observe blazars simultaneously at di…
HAWC J2227+610 and its association with G106.3+2.7, a new potential Galactic PeVatron
A. Albert, R. Alfaro, C. Alvarez +97
We present the detection of VHE gamma-ray emission above 100 TeV from HAWC J2227+610 with the HAWC observatory. Combining our observations with previously published results by VERI…
HAWC Contributions to the 35th International Cosmic Ray Conference (ICRC2017)
A. U. Abeysekara, A. Albert, R. Alfaro +123
List of proceedings from the HAWC Collaboration presented at the 35th International Cosmic Ray Conference, 12 July - 20 July 2017, Bexco, Busan, Korea.
A Search for Pulsations from Geminga Above 100 GeV with VERITAS
E. Aliu, S. Archambault, A. Archer +81
We present the results of 71.6 hours of observations of the Geminga pulsar (PSR J0633+1746) with the VERITAS very-high-energy gamma-ray telescope array. Data taken with VERITAS bet…
Discovery of Very High Energy Gamma Rays from 1ES 1440+122
VERITAS Collaboration, S. Archambault, A. Archer +87
The BL Lacertae object 1ES 1440+122 was observed in the energy range from 85 GeV to 30 TeV by the VERITAS array of imaging atmospheric Cherenkov telescopes. The observations, taken…
Gamma-ray observations of Tycho's SNR with VERITAS and Fermi
VERITAS Collaboration, S. Archambault, A. Archer +64
High-energy gamma-ray emission from supernova remnants (SNRs) has provided a unique perspective for studies of Galactic cosmic-ray acceleration. Tycho's SNR is a particularly good…
3HWC: The Third HAWC Catalog of Very-High-Energy Gamma-ray Sources
A. Albert, R. Alfaro, C. Alvarez +104
We present a new catalog of TeV gamma-ray sources using 1523 days of data from the High Altitude Water Cherenkov (HAWC) observatory. The catalog represents the most sensitive surve…
Constraints on Spin-Dependent Dark Matter Scattering with Long-Lived Mediators from TeV Observations of the Sun with HAWC
A. Albert, R. Alfaro, C. Alvarez +91
We analyze the Sun as a source for the indirect detection of dark matter through a search for gamma rays from the solar disk. Capture of dark matter by elastic interactions with th…
Science Case for a Wide Field-of-View Very-High-Energy Gamma-Ray Observatory in the Southern Hemisphere
A. Albert, R. Alfaro, H. Ashkar +100
We outline the science motivation for SGSO, the Southern Gamma-Ray Survey Observatory. SGSO will be a next-generation wide field-of-view gamma-ray survey instrument, sensitive to g…
Very-High-Energy -Ray Observations of the Blazar 1ES 2344+514 with VERITAS
C. Allen, S. Archambault, A. Archer +79
We present very-high-energy -ray observations of the BL Lac object 1ES 2344+514 taken by the Very Energetic Radiation Imaging Telescope Array System (VERITAS) between 2007 and…
Constraints on Lorentz invariance violation from HAWC observations of gamma rays above 100 TeV
HAWC Collaboration, A. Albert, R. Alfaro +90
Due to the high energies and long distances to the sources, astrophysical observations provide a unique opportunity to test possible signatures of Lorentz invariance violation (LIV…
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…
Exceptionally bright TeV flares from the binary LS I +61 303
VERITAS Collaboration, S. Archambault, A. Archer +86
The TeV binary system LS I +61 303 is known for its regular, non-thermal emission pattern which traces the orbital period of the compact object in its 26.5 day orbit around…
Very High Energy outburst of Markarian 501 in May 2009
E. Aliu, S. Archambault, A. Archer +108
The very high energy (VHE; E 100 GeV) blazar Markarian 501 was observed between April 17 and May 5 (MJD 54938--54956), 2009, as part of an extensive multi-wavelength campaign f…
The 2009 multiwavelength campaign on Mrk 421: Variability and correlation studies
MAGIC Collaboration, J. AleksiÄ, S. Ansoldi +270
We performed a 4.5-month multi-instrument campaign (from radio to VHE gamma rays) on Mrk421 between January 2009 and June 2009, which included VLBA, F-GAMMA, GASP-WEBT, Swift, RXTE…
A Search for Dark Matter in the Galactic Halo with HAWC
A. U. Abeysekara, A. M. Albert, R. Alfaro +100
The High Altitude Water Cherenkov (HAWC) gamma-ray observatory is a wide field-of-view observatory sensitive to 500 GeV - 100 TeV gamma rays and cosmic rays. With its observations…
Search for Very High Energy Gamma Rays from the Northern Bubble Region with HAWC
A. U. Abeysekara, A. Albert, R. Alfaro +108
We present a search of very high energy gamma-ray emission from the Northern Bubble region using data collected with the High Altitude Water Cherenkov (HAWC) gamma…
VERITAS contributions to the 35th International Cosmic Ray Conference
A. U. Abeysekara, S. Archambault, A. Archer +63
Compilation of papers presented by the VERITAS Collaboration at the 35th International Cosmic Ray Conference (ICRC), held July 12 through July 20, 2017 in Busan, South Korea.
Gamma-ray Observations Under Bright Moonlight with VERITAS
S. Archambault, A. Archer, W. Benbow +62
Imaging atmospheric Cherenkov telescopes (IACTs) are equipped with sensitive photomultiplier tube (PMT) cameras. Exposure to high levels of background illumination degrades the eff…
TeV Gamma-ray Observations of The Galactic Center Ridge By VERITAS
A. Archer, W. Benbow, R. Bird +73
The Galactic Center Ridge has been observed extensively in the past by both GeV and TeV gamma-ray instruments revealing a wealth of structure, including a diffuse component as well…
Multiple Galactic Sources with Emission Above 56 TeV Detected by HAWC
HAWC Collaboration, A. U. Abeysekara, A. Albert +99
We present the first catalog of gamma-ray sources emitting above 56 and 100 TeV with data from the High Altitude Water Cherenkov (HAWC) Observatory, a wide field-of-view observator…
A Search for Brief Optical Flashes Associated with the SETI Target KIC 8462852
A. U. Abeysekara, S. Archambault, A. Archer +78
The F-type star KIC 8462852 has recently been identified as an exceptional target for SETI (search for extraterrestrial intelligence) observations. We describe an analysis methodol…
Very High-Energy Gamma-Ray Follow-Up Program Using Neutrino Triggers from IceCube
IceCube Collaboration, M. G. Aartsen, K. Abraham +537
We describe and report the status of a neutrino-triggered program in IceCube that generates real-time alerts for gamma-ray follow-up observations by atmospheric-Cherenkov telescope…
VERITAS and Multiwavelength Observations of the BL Lacertae Object 1ES 1741+196
VERITAS Collaboration, A. U. Abeysekara, S. Archambault +85
We present results from multiwavelength observations of the BL Lacertae object 1ES 1741+196, including results in the very-high-energy -ray regime using the Very Energetic Radi…
Investigating Broadband Variability of the TeV Blazar 1ES 1959+650
E. Aliu, S. Archambault, T. Arlen +92
We summarize broadband observations of the TeV-emitting blazar 1ES 1959+650, including optical R-band observations by the robotic telescopes Super-LOTIS and iTelescope, UV observat…
A Search for Very High-Energy Gamma Rays from the Missing Link Binary Pulsar J1023+0038 with VERITAS
E. Aliu, S. Archambault, A. Archer +82
The binary millisecond radio pulsar PSR J1023+0038 exhibits many characteristics similar to the gamma-ray binary system PSR B1259--63/LS 2883, making it an ideal candidate for the…
Science Highlights from VERITAS
D. Staszak, A. U. Abeysekara, S. Archambault +88
The Very Energetic Radiation Imaging Telescope Array System (VERITAS) is a ground-based array located at the Fred Lawrence Whipple Observatory in southern Arizona and is one of the…
Multiwavelength Study of Quiescent States of Mrk 421 with Unprecedented Hard X-Ray Coverage Provided by NuSTAR in 2013
M. BalokoviÄ, D. Paneque, G. Madejski +305
We present coordinated multiwavelength observations of the bright, nearby BL Lac object Mrk 421 taken in 2013 January-March, involving GASP-WEBT, Swift, NuSTAR, Fermi-LAT, MAGIC, V…
A luminous and isolated gamma-ray flare from the blazar B2 1215+30
VERITAS Collaboration, A. U. Abeysekara, S. Archambault +84
B2 1215+30 is a BL Lac-type blazar that was first detected at TeV energies by the MAGIC atmospheric Cherenkov telescopes, and subsequently confirmed by the VERITAS observatory with…
HAWC observations of the acceleration of very-high-energy cosmic rays in the Cygnus Cocoon
A. U. Abeysekara, A. Albert, R. Alfaro +98
Cosmic rays with energies up to a few PeV are known to be accelerated within the Milky Way. Traditionally, it has been presumed that supernova remnants were the main source of very…
Search for Magnetically Broadened Cascade Emission From Blazars with VERITAS
VERITAS Collaboration, S. Archambault, A. Archer +53
We present a search for magnetically broadened gamma-ray emission around active galactic nuclei (AGN), using VERITAS observations of seven hard-spectrum blazars. A cascade process…
Constraints on Very High Energy Emission from GRB 130427A
E. Aliu, T. Aune, A. Barnacka +89
Prompt emission from the very fluent and nearby (z=0.34) gamma-ray burst GRB 130427A was detected by several orbiting telescopes and by ground-based, wide-field-of-view optical tra…
Measurement of the Iron Spectrum in Cosmic Rays by VERITAS
The VERITAS collaboration, A. Archer, W. Benbow +55
We present a new measurement of the energy spectrum of iron nuclei in cosmic rays from 20 to 500 TeV. The measurement makes use of a template-based analysis method, which, for the…
Very-high-energy observations of the binaries V 404 Cyg and 4U 0115+634 during giant X-ray outbursts
A. Archer, W. Benbow, R. Bird +62
Transient X-ray binaries produce major outbursts in which the X-ray flux can increase over the quiescent level by factors as large as . The low-mass X-ray binary V 404 Cyg an…
A Very High Energy -Ray Survey towards the Cygnus Region of the Galaxy
The VERITAS Collaboration, A. U. Abeysekara, A. Archer +68
We present results from deep observations towards the Cygnus region using 300 hours of very-high-energy (VHE) -ray data taken with the VERITAS Cherenkov telescope array and ove…
HAWC and Fermi-LAT Detection of Extended Emission from the Unidentified Source 2HWC J2006+341
A. Albert, R. Alfaro, C. Alvarez +71
The discovery of the TeV point source 2HWC J2006+341 was reported in the second HAWC gamma-ray catalog. We present a follow-up study of this source here. The TeV emission is best d…
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)…
Improving the low-energy transient sensitivity of AMEGO-X using single-site events
I. Martinez-Castellanos, H. Fleischhack, C. Karwin +14
AMEGO-X, the All-sky Medium Energy Gamma-Ray Observatory eXplorer, is a proposed instrument designed to bridge the so-called "MeV gap" by surveying the sky with unprecedented sensi…
Evidence of 200 TeV photons from HAWC J1825-134
A. Albert, R. Alfaro, C. Alvarez +81
The Earth is bombarded by ultra-relativistic particles, known as cosmic rays (CRs). CRs with energies up to a few PeV (=10 eV), the knee in the particle spectrum, are believ…
Multiband variability studies and novel broadband SED modeling of Mrk 501 in 2009
M. L. Ahnen, S. Ansoldi, L. A. Antonelli +290
We present an extensive study of the BL Lac object Mrk 501 based on a data set collected during the multi-instrument campaign spanning from 2009 March 15 to 2009 August 1 which inc…
The Southern Wide-Field Gamma-Ray Observatory (SWGO): A Next-Generation Ground-Based Survey Instrument for VHE Gamma-Ray Astronomy
P. Abreu, A. Albert, R. Alfaro +95
We describe plans for the development of the Southern Wide-field Gamma-ray Observatory (SWGO), a next-generation instrument with sensitivity to the very-high-energy (VHE) band to b…
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…
CTA Contributions to the 34th International Cosmic Ray Conference (ICRC2015)
The CTA Consortium, :, A. Abchiche +1305
List of contributions from the CTA Consortium presented at the 34th International Cosmic Ray Conference, 30 July - 6 August 2015, The Hague, The Netherlands.
Investigating the TeV Morphology of MGRO J1908+06 with VERITAS
E. Aliu, S. Archambault, T. Aune +85
We report on deep observations of the extended TeV gamma-ray source MGRO J1908+06 made with the VERITAS very high energy (VHE) gamma-ray observatory. Previously, the TeV emission h…
All-Sky Measurement of the Anisotropy of Cosmic Rays at 10 TeV and Mapping of the Local Interstellar Magnetic Field
HAWC Collaboration, A. U. Abeysekara, R. Alfaro +400
We present the first full-sky analysis of the cosmic ray arrival direction distribution with data collected by the HAWC and IceCube observatories in the Northern and Southern hemis…
A Contribution of the HAWC Observatory to the TeV era in the High Energy Gamma-Ray Astrophysics: The case of the TeV-Halos
Ramiro Torres-Escobedo, Hao Zhou, Eduardo de la Fuente +130
We present a short overview of the TeV-Halos objects as a discovery and a relevant contribution of the High Altitude Water Äerenkov (HAWC) observatory to TeV astrophysics. We disc…
The High-Altitude Water Cherenkov (HAWC) Observatory in México: The Primary Detector
A. U. Abeysekara, A. Albert, R. Alfaro +140
The High-Altitude Water Cherenkov (HAWC) observatory is a second-generation continuously operated, wide field-of-view, TeV gamma-ray observatory. The HAWC observatory and its analy…
A Three-Year Multi-Wavelength Study of the Very High Energy Gamma-ray Blazar 1ES 0229+200
E. Aliu, S. Archambault, T. Arlen +83
The high-frequency-peaked BL Lacertae object 1ES 0229+200 is a relatively distant (z = 0.1396), hard-spectrum (Gamma ~ 2.5), very-high-energy-emitting (E > 100 GeV) gamma-ray blaza…
Deep Broadband Observations of the Distant Gamma-ray Blazar PKS 1424+240
S. Archambault, T. Aune, B. Behera +149
We present deep VERITAS observations of the blazar PKS 1424+240, along with contemporaneous Fermi Large Area Telescope, Swift X-ray Telescope and Swift UV Optical Telescope data be…
Contributions of the Cherenkov Telescope Array (CTA) to the 6th International Symposium on High-Energy Gamma-Ray Astronomy (Gamma 2016)
The CTA Consortium, :, A. Abchiche +1387
List of contributions from the Cherenkov Telescope Array (CTA) Consortium presented at the 6th International Symposium on High-Energy Gamma-Ray Astronomy (Gamma 2016), July 11-15,…
All-particle cosmic ray energy spectrum measured by the HAWC experiment from 10 to 500 TeV
HAWC Collaboration, R. Alfaro, C. Alvarez +98
We report on the measurement of the all-particle cosmic ray energy spectrum with the High Altitude Water Cherenkov (HAWC) Observatory in the energy range 10 to 500 TeV. HAWC is a g…
Gamma rays from the quasar PKS 1441+25: story of an escape
A. U. Abeysekara, S. Archambault, A. Archer +103
Outbursts from gamma-ray quasars provide insights on the relativistic jets of active galactic nuclei and constraints on the diffuse radiation fields that fill the Universe. The det…
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…
Constraints on the Emission of Gamma Rays from M31 with HAWC
HAWC Collaboration, A. Albert, R. Alfaro +82
Cosmic rays, along with stellar radiation and magnetic fields, are known to make up a significant fraction of the energy density of galaxies such as the Milky Way. When cosmic rays…
Multiwavelength follow-up of a rare IceCube neutrino multiplet
M. G. Aartsen, M. Ackermann, J. Adams +501
On February 17 2016, the IceCube real-time neutrino search identified, for the first time, three muon neutrino candidates arriving within 100 s of one another, consistent with comi…
CTA contributions to the 33rd International Cosmic Ray Conference (ICRC2013)
The CTA Consortium, :, O. Abril +1102
Compilation of CTA contributions to the proceedings of the 33rd International Cosmic Ray Conference (ICRC2013), which took place in 2-9 July, 2013, in Rio de Janeiro, Brazil
Pulsars in a Bubble? Following Electron Diffusion in the Galaxy with TeV Gamma Rays
H. Fleischhack, A. Albert, C. Alvarez +32
TeV Halos, extended regions of TeV gamma-ray emission around middle-aged pulsars, have recently been established as a new source class in gamma-ray astronomy. These halos have been…
The most powerful flaring activity from the NLSy1 PMN J0948+0022
F. D'Ammando, M. Orienti, J. Finke +73
We report on multifrequency observations performed during 2012 December-2013 August of the first narrow-line Seyfert 1 galaxy detected in gamma rays, PMN J0948+0022 ( = 0.5846).…
Catalog of Long-Term Transient Sources in the First 10 Years of Fermi-LAT Data
L. Baldini, J. Ballet, D. Bastieri +112
We present the first Fermi Large Area Telescope (LAT) catalog of long-term -ray transient sources (1FLT). This comprises sources that were detected on monthly time intervals du…
HAWC Contributions to the 36th International Cosmic Ray Conference (ICRC2019)
A. U. Abeysekara, A. Albert, R. Alfaro +127
List of proceedings from the HAWC Collaboration presented at the 36th International Cosmic Ray Conference, 24 July - 1 August 2019, Madison, Wisconsin, USA.
VERITAS detection of -ray flaring activity from the BL Lac object 1ES 1727+502 during bright moonlight observations
S. Archambault, A. Archer, M. Beilicke +80
During moonlit nights, observations with ground-based Cherenkov telescopes at very high energies (VHE, GeV) are constrained since the photomultiplier tubes (PMTs) in the te…
Discovery of very-high-energy emission from RGB J2243+203 and derivation of its redshift upper limit
A. U. Abeysekara, S. Archambault, A. Archer +67
Very-high-energy (VHE; 100 GeV) gamma-ray emission from the blazar RGB J2243+203 was discovered with the VERITAS Cherenkov telescope array, during the period between 21 and 24…
Upper limits from five years of blazar observations with the VERITAS Cherenkov telescopes
S. Archambault, A. Archer, W. Benbow +78
Between the beginning of its full-scale scientific operations in 2007 and 2012, the VERITAS Cherenkov telescope array observed more than 130 blazars; of these, 26 were detected as…
First HAWC Observations of the Sun Constrain Steady TeV Gamma-Ray Emission
A. Albert, R. Alfaro, C. Alvarez +92
Steady gamma-ray emission up to at least 200 GeV has been detected from the solar disk in the Fermi-LAT data, with the brightest, hardest emission occurring during solar minimum. T…
Multimessenger Gamma-Ray and Neutrino Coincidence Alerts using HAWC and IceCube sub-threshold Data
H. A. Ayala Solares, S. Coutu, J. J. DeLaunay +446
The High Altitude Water Cherenkov (HAWC) and IceCube observatories, through the Astrophysical Multimessenger Observatory Network (AMON) framework, have developed a multimessenger j…
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…
VERITAS Collaboration Contributions to the 34th International Cosmic Ray Conference
The VERITAS Collaboration, A. U. Abeysekara, S. Archambault +90
Compilation of papers presented by the VERITAS Collaboration at the 34th International Cosmic Ray Conference (ICRC), held July 30 through August 6, 2015 in The Hague, The Netherlan…
Dark Matter Constraints from a Joint Analysis of Dwarf Spheroidal Galaxy Observations with VERITAS
VERITAS Collaboration, S. Archambault, A. Archer +69
We present constraints on the annihilation cross section of WIMP dark matter based on the joint statistical analysis of four dwarf galaxies with VERITAS. These results are derived…
The TeV Sun Rises: Discovery of Gamma rays from the Quiescent Sun with HAWC
A. Albert, R. Alfaro, C. Alvarez +89
We report the first detection of a TeV gamma-ray flux from the solar disk (6.3), based on 6.1 years of data from the High Altitude Water Cherenkov (HAWC) observatory. The 0.5--…
Searching for Dark Matter Sub-structure with HAWC
A. U. Abeysekara, A. Albert, R. Alfaro +75
Simulations of dark matter show a discrepancy between the expected number of Galactic dark matter sub-halos and how many have been optically observed. Some of these unseen satellit…
Measurement of the Crab Nebula Spectrum Past 100 TeV with HAWC
HAWC Collaboration, A. U. Abeysekara, A. Albert +102
We present TeV gamma-ray observations of the Crab Nebula, the standard reference source in ground-based gamma-ray astronomy, using data from the High Altitude Water Cherenkov (HAWC…
Constraining the Local Burst Rate Density of Primordial Black Holes with HAWC
A. Albert, R. Alfaro, C. Alvarez +84
Primordial Black Holes (PBHs) may have been created by density fluctuations in the early Universe and could be as massive as solar masses or as small as the Planck mass. I…