A search was conducted for TeV γ-rays emitted from the direction of the ultra-high-energy cosmic ray detected by the Fly's Eye experiment with energy E ~ 3 × 1020 eV. No enhancement was found at a level of 10-10γ cm-2 s-1 for E > 350 GeV. A steady source of ultra-high-energy cosmic ray protons or photons would be expected to produce a γ-ray flux above this level. An upper limit was also set for the flux of TeV γ-rays from 3C 147, the most prominent active galactic nucleus in the error box.
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 has been attributed to the pulsar wind nebula (PWN) of the Fermi-LAT pulsar PSR J1907+0602. We detect MGRO J1908+06 at a significance level of 14 standard deviations (14 sigma) and measure a photon index of 2.20 +/- 0.10_stat +/- 0.20_sys. The TeV emission is extended, covering the region near PSR J1907+0602 and also extending towards SNR G40.5--0.5. When fitted with a 2-dimensional Gaussian, the intrinsic extension has a standard deviation of sigma_src = 0.44 +/- 0.02 degrees. In contrast to other TeV PWNe of similar age in which the TeV spectrum softens with distance from the pulsar, the TeV spectrum measured near the pulsar location is consistent with that measured at a position near the rim of G40.5--0.5, 0.33 degrees away.
VTSCat is the catalog of high-level data products from all publications of the VERITAS collaboration. Most recent versions of VTSCat are available through https://doi.org/10.5281/zenodo.6988967 The VTSCat data collection contains: high-level data like spectral flux points, light curves, spectral fits in human- and machine-readable yaml and ecsv file format tabled data like upper limits tables from dark matter searches or results on the extragalactic background in ecsv file format sky maps (wherever available) in FITS file format The data collection contains results from gamma-ray measurements only. This is a pre-release for testing and early publications. A forthcoming research note will provide more details on the catalog. Please check the README file and all documentation linked to the README. VTSCat supplements the HEASARC catalogue of VERITAS results (to be published). VTSCat is inspired and derived from gamma-cat. If you are a previous VERITAS author and would like to be associated with this repository, please send an email to G. Maier. Access: GitHub: https://github.com/VERITAS-Observatory/VERITAS-VTSCat References: VERITAS: https://veritas.sao.arizona.edu/ VER Dictionary of Nomenclature: https://cds.u-strasbg.fr/cgi-bin/Dic-Simbad?/17350620
VTSCat is the catalog of high-level data products from all publications of the VERITAS collaboration. The VTSCat data collection contains: high-level data like spectral flux points, light curves, spectral fits in human and machine-readable yaml and ecsv file format tabled data like upper limits tables from dark matter searches or results on the extragalactic background in ecsv file format sky maps (wherever available) in FITS file format A detailed description of VTSCat can be found in A. Acharyya et al 2023 Res. Notes AAS 7 6. Please check also the README file and all documentation linked to the README. VTSCat supplements the HEASARC catalogue of VERITAS results, accessible through this link. VTSCat is inspired and derived from gamma-cat. If you are a previous VERITAS author and would like to be associated with this repository, please send an email to G. Maier. Access: GitHub: https://github.com/VERITAS-Observatory/VERITAS-VTSCat HEASARC: https://heasarc.gsfc.nasa.gov/W3Browse/all/verimaster.html References: https://veritas.sao.arizona.edu/ VER Dictionary of Nomenclature: https://cds.u-strasbg.fr/cgi-bin/Dic-Simbad?/17350620 GitHub: https://github.com/VERITAS-Observatory/VERITAS-VTSCat HEASARC: https://heasarc.gsfc.nasa.gov/W3Browse/all/verimaster.html Research note A. Acharyya et al 2023 Res. Notes AAS 7 6; see also arXiv:2301.04498 ICRC 2021 proceedings: https://arxiv.org/abs/2108.06424
Two active galactic nuclei have been detected at TeV energies using the atmospheric Cerenkov imaging technique. The Whipple Observatory γ-ray telescope has been used to observe all the BL Lacertae objects in the northern hemisphere out to a redshift of 0.1. We report the tentative detection of VHE emission from a third BL Lac object, 1ES 2344+514. Progress in extending this survey out to z=0.2 will also be reported. INTRODUCTION With the detection of very high energy (VHE, E > 250 GeV) emission from the two BL Lacertae objects (BL Lacs) , Markarian 421 (Mrk 421) (Punch et al. 1992) and Mrk 501 (Quinn et al. 1996), we began a survey of nearby BL Lacs to search for VHE emission. A collection of such sources could lead to constraintes on γ-ray emission models through investigation into the properties which are important for VHE emission and also an estimate of the density of extragalactic background IR light through its effect on the VHE γ-ray spectra (Gould and Schreder 1967; Stecker, de Jager, & Salamon 1993). BL Lacs are blazars, the only type of active galactic nucleus (AGN) detected above 100 MeV. The electromagnetic spectrum of blazars consists of synchrotron emission, which spans radio to UV or X-ray wavelengths, produced by electrons moving within jets oriented at small angles to our line of sight (Blandford & Konigl 1981), and a high energy part which can extend to γ-ray energies. Models of the high energy emission fall into three main categories: synchrotron self-Compton emission (e.g., Konigl 1981), inverse-Compton scattering of low energy photons arising outside the jet (e.g., Sikora, Begelman, and Rees 1994), and pair cascades initiated by protons (Mannheim 1993) or electrons. If protons produce the high energy emission, AGN could contribute significantly to the highest energy cosmic-ray flux (E > 1018eV) (Rachen, Stanev, and Biermann 1993). BL Lacs are particularly promising candidates for VHE emission because of two aspects of their low energy emission. First, BL Lacs may have less γ-ray absorbing material near the source because they have weak or no emission lines in their optical spectra (Dermer and Schlickeiser 1994). Second, in inverse Compton (IC) models of the high energy emission, the extension of the synchrotron emission of X-ray selected BL Lacs (e.g., Mrk 421 and Mrk 501) into the X-ray waveband implies a higher maximum γ-ray energy than for radio-loud BL Lacs (e.g., W Comae) and flat spectrum radio quasars (e.g., 3C 279) where the synchrotron emission ends in the optical to UV range. Table 1 lists the objects observed in our BL Lac survey so far. We have limited our search to BL Lacs with z 350 GeV) = 8.7× 10−11 photons cm−2 s−1 (Hillas et al. 1997). This procedure assumes that the Crab Nebula VHE γ-ray flux is constant, as 7 years of Whipple Observatory data indicate (Hillas et al. 1997), and that the object’s photon spectrum is identical to that of the Crab Nebula between 0.3 and 10 TeV, dN/dE ∝ E−2.4 (Hillas et al. 1997), which may not be the case. If no significant emission is seen from a candidate source, a 99.9% confidence upper limit is calculated using the method of Helene (1983). RESULTS In Table 1 we present the results of observations for which the analysis has been completed. With the exception of 1ES 2344+514, there is no evidence of emission from any of the objects in this survey. In particular, the EGRET sources W Comae (von Montigny et al. 1995) and BL Lacertae (Catanese et al. 1997a) are not detected despite long exposures. Also, only 1ES 2344+514 shows evidence of short term activity. Most of the excess from 1ES 2344+514 during 1995 comes from an apparent flare on 1995 December 20 (see Figure 1). We find a non-statistically significant excess from this object in 1996 which could simply mean that the average flux level dropped below the telescope sensitivity limit, as occasionally happens with Mrk 421 (Buckley et al. 1996). We currently consider the detection tentative because we see no evidence for a consistent signal nor is there independent confirmation of a high state for this object (e.g., from X-ray observations) during this period. Max. Observ. Exp. Daily Flux Object z Typea Epoch (hrs) Excess Exc. (Crab)b Fluxc 1ES 2344+514 0.044 X 1995/96 20.5 5.3σ 6.0σ 0.16±0.03 1.4±0.3 20-12-95 1.8 6.0σ 0.63±0.11 5.5±1.
VERITAS is one of the world’s most sensitive detectors of astrophysical VHE (E > 100 GeV) gamma rays. This array of four 12-m imaging atmospheric Cherenkov telescopes, located in southern Arizona, USA, has operated for ~15 years. VERITAS science spans Galactic topics, including pulsar wind nebulae, binary systems, and supernova remnants; extra-galactic topics, including studies of blazars and radio galaxies, searches for gamma-ray bursts and fast radio bursts; multi-messenger science; and astroparticle physics topics including searches for dark matter. VERITAS has also pioneered the use of IACTs for optical astronomy, particularly via intensity interferometry. Recent highlights from the VERITAS observing program and scientific results are presented.
We present constraints on the annihilation cross section of weakly interacting massive particles dark matter based on the joint statistical analysis of four dwarf galaxies with VERITAS. These results are derived from an optimized photon weighting statistical technique that improves on standard imaging atmospheric Cherenkov telescope (IACT) analyses by utilizing the spectral and spatial properties of individual photon events. We report on the results of $\ensuremath{\sim}230$ hours of observations of five dwarf galaxies and the joint statistical analysis of four of the dwarf galaxies. We find no evidence of gamma-ray emission from any individual dwarf nor in the joint analysis. The derived upper limit on the dark matter annihilation cross section from the joint analysis is $1.35\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}23}\text{ }\text{ }{\mathrm{cm}}^{3}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$ at 1 TeV for the bottom quark ($b\overline{b}$) final state, $2.85\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}24}\text{ }\text{ }{\mathrm{cm}}^{3}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$ at 1 TeV for the tau lepton (${\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$) final state and $1.32\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}25}\text{ }\text{ }{\mathrm{cm}}^{3}\text{ }{\mathrm{s}}^{\ensuremath{-}1}$ at 1 TeV for the gauge boson ($\ensuremath{\gamma}\ensuremath{\gamma}$) final state.
The process of gathering and associating data from multiple sensors or sub-detectors due to a common physical event (the process of event-building) is used in many fields, including high-energy physics and $\gamma$-ray astronomy. Fault tolerance in event-building is a challenging problem that increases in difficulty with higher data throughput rates and increasing numbers of sub-detectors. We draw on biological self-assembly models in the development of a novel event-building paradigm that treats each packet of data from an individual sensor or sub-detector as if it were a molecule in solution. Just as molecules are capable of forming chemical bonds, bonds can be defined between data packets using metadata-based discriminants. A database -- which plays the role of a beaker of solution -- continually selects pairs of assemblies at random to test for bonds, which allows single packets and small assemblies to aggregate into larger assemblies. During this process higher-quality associations supersede spurious ones. The database thereby becomes fluid, dynamic, and self-correcting rather than static. We will describe tests of the self-assembly paradigm using our first fluid database prototype and data from the VERITAS $\gamma$-ray telescope.
Only BL Lac objects have been detected as extragalactic sources of very high energy (E > 300 GeV) gamma rays. Using the Whipple Observatory Gamma-ray Telescope, we have attempted to detect more BL Lacs using three approaches. First, we have conducted surveys of nearby BL Lacs, which led to the detections of Mrk 501 and 1ES 2344+514. Second, we have observed X-ray bright BL Lacs when the RXTE All-Sky Monitor identifies high state X-ray emission in an object, in order to efficiently detect extended high emission states. Third, we have conducted rapid observations of several BL Lacs and QSOs located close together in the sky to search for very high flux, short time-scale flare states such as have been seen from Mrk 421. We will present the results of a survey using the third observational technique.
Abstract 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 gamma-ray emission ( E γ > 100 GeV) followed by the recent detection of ultrahigh-energy gamma-ray emission ( E γ > 100 TeV) from the tail region suggests that G106.3+2.7 is a PeVatron candidate. We present a comprehensive multiwavelength study of the Boomerang PWN (100″ around PSR J2229+6114) using archival radio and Chandra data obtained two decades ago, a new NuSTAR X-ray observation from 2020, and upper limits on gamma-ray fluxes obtained by Fermi-LAT and VERITAS observatories. The NuSTAR observation allowed us to detect a 51.67 ms spin period from the pulsar PSR J2229+6114 and the PWN emission characterized by a power-law model with Γ = 1.52 ± 0.06 up to 20 keV. Contrary to the previous radio study by Kothes et al., we prefer a much lower PWN B -field ( B ∼ 3 μ G) and larger distance ( d ∼ 8 kpc) based on (1) the nonvarying X-ray flux over the last two decades, (2) the energy-dependent X-ray size of the PWN resulting from synchrotron burn-off, and (3) the multiwavelength spectral energy distribution (SED) data. Our SED model suggests that the PWN is currently re-expanding after being compressed by the SNR reverse shock ∼1000 yr ago. In this case, the head region should be formed by GeV–TeV electrons injected earlier by the pulsar propagating into the low-density environment.
