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 survey of the northern ...gamma-ray sky at energies above several TeV, with three times the exposure compared to the previous HAWC catalog, 2HWC. We report 65 sources detected at ≥5 significance, along with the positions and spectral fits for each source. The catalog contains eight sources that have no counterpart in the 2HWC catalog, but are within 1° of previously detected TeV emitters, and 20 sources that are more than 1° away from any previously detected TeV source. Of these 20 new sources, 14 have a potential counterpart in the fourth Fermi Large Area Telescope catalog of gamma-ray sources. We also explore potential associations of 3HWC sources with pulsars in the Australia Telescope National Facility (ATNF) pulsar catalog and supernova remnants in the Galactic supernova remnant catalog.
We present the first catalog of gamma-ray sources emitting above 56 and 100 TeV with data from the High Altitude Water Cherenkov Observatory, a wide field-of-view observatory capable of detecting ...gamma rays up to a few hundred TeV. Nine sources are observed above 56 TeV, all of which are likely galactic in origin. Three sources continue emitting past 100 TeV, making this the highest-energy gamma-ray source catalog to date. We report the integral flux of each of these objects. We also report spectra for three highest-energy sources and discuss the possibility that they are PeVatrons.
The 2HWC HAWC Observatory Gamma-Ray Catalog Abeysekara, A. U.; Albert, A.; Alfaro, R. ...
Astrophysical journal/The Astrophysical journal,
07/2017, Letnik:
843, Številka:
1
Journal Article
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We present the first catalog of TeV gamma-ray sources realized with data from the newly completed High Altitude Water Cherenkov Observatory (HAWC). It is the most sensitive wide field-of-view TeV ...telescope currently in operation, with a one-year survey sensitivity of ∼5%-10% of the flux of the Crab Nebula. With an instantaneous field of view >1.5 sr and >90% duty cycle, it continuously surveys and monitors the sky for gamma-ray energies between hundreds of GeV and tens of TeV. HAWC is located in Mexico, at a latitude of 19° N, and was completed in 2015 March. Here, we present the 2HWC catalog, which is the result of the first source search performed with the complete HAWC detector. Realized with 507 days of data, it represents the most sensitive TeV survey to date for such a large fraction of the sky. A total of 39 sources were detected, with an expected number of false detections of 0.5 due to background fluctuation. Out of these sources, 19 are new sources that are not associated with previously known TeV sources (association criteria: <0 5 away). The source list, including the position measurement, spectrum measurement, and uncertainties, is reported, then each source is briefly discussed. Of the 2HWC associated sources, 10 are reported in TeVCat as PWN or SNR: 2 as blazars and the remaining eight as unidentified.
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) Gamma-Ray ...Observatory. In this analysis we use two independent energy estimation methods that utilize extensive air shower variables such as the core position, shower angle, and shower lateral energy distribution. In contrast, the previously published HAWC energy spectrum roughly estimated the shower energy with only the number of photomultipliers triggered. This new methodology yields a much-improved energy resolution over the previous analysis and extends HAWC's ability to accurately measure gamma-ray energies well beyond 100 TeV. The energy spectrum of the Crab Nebula is well fit to a log-parabola shape with emission up to at least 100 TeV. For the first estimator, a ground parameter that utilizes fits to the lateral distribution function to measure the charge density 40 m from the shower axis, the best-fit values are (TeV cm2 s)−1, , and . For the second estimator, a neural network that uses the charge distribution in annuli around the core and other variables, these values are (TeV cm2 s)−1, , and β = 0.06 0.01 0.02. The first set of uncertainties is statistical; the second set is systematic. Both methods yield compatible results. These measurements are the highest-energy observation of a gamma-ray source to date.
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. It can also perform diverse indirect ...searches for dark matter annihilation and decay. Among the most promising targets for the indirect detection of dark matter are dwarf spheroidal galaxies. These objects are expected to have few astrophysical sources of gamma-rays but high dark matter content, making them ideal candidates for an indirect dark matter detection with gamma-rays. Here we present individual limits on the annihilation cross section and decay lifetime for 15 dwarf spheroidal galaxies within the field of view, as well as their combined limit. These are the first limits on the annihilation cross section and decay lifetime using data collected with HAWC. We also present the HAWC flux upper limits of the 15 dwarf spheroidal galaxies in half-decade energy bins.
We present the detection of very-high-energy gamma-ray emission above 100 TeV from HAWC J2227+610 with the High-Altitude Water Cherenov Gamma-Ray Observatory (HAWC) observatory. Combining our ...observations with previously published results by the Very Energetic Radiation Imaging Telescope Array System (VERTIAS), we interpret the gamma-ray emission from HAWC J2227+610 as emission from protons with a lower limit in their cutoff energy of 800 TeV. The most likely source of the protons is the associated supernova remnant G106.3+2.7, making it a good candidate for a Galactic PeVatron. However, a purely leptonic origin of the observed emission cannot be excluded at this time.
Because of the high energies and long distances to the sources, astrophysical observations provide a unique opportunity to test possible signatures of Lorentz invariance violation (LIV). Superluminal ...LIV enables the decay of photons at high energy. The high altitude water Cherenkov (HAWC) observatory is among the most sensitive gamma-ray instruments currently operating above 10 TeV. HAWC finds evidence of 100 TeV photon emission from at least four astrophysical sources. These observations exclude, for the strongest of the limits set, the LIV energy scale to 2.2×10^{31} eV, over 1800 times the Planck energy and an improvement of 1 to 2 orders of magnitude over previous limits.
Curcumin is a promising natural drug in cancer therapy. However, its therapeutic applicability is limited by its low solubility, short half‐life, and low bioavailability. In this work curcumin is ...encapsulated in stimuli‐responsive magneto‐polymeric nanoplatforms aiming at improving its bioavailability and efficiency for delivery in biological media. MnFe2O4 magnetic nanoparticles (MNPs) were synthesized via thermal decomposition, coated with sodium citrate and then functionalized with multilayers of chitosan and sodium alginate, by means of the layer‐by‐layer deposition technique. A mesoporous polymeric‐magnetic nanoplatform was produced capable of a controlled and sustained release of curcumin under temperature, pH and alternating magnetic field (magnetic hyperthermia) stimuli. As the temperature and pH of the medium increased, an increase in the rate of curcumin release was observed in a two‐stage process, following the Gallagher‐Corrigan mathematical model. The use of magnetic hyperthermia resulted in a faster diffusion‐based release of curcumin. Increasing the number of polymer layers assembled on top of MNPs hinders the release of the curcumin molecules from innermost regions of the multilayers. These results show that magnetic hyperthermia provides a means for the controlled heat‐induced release of curcumin, which can lead to an enhanced therapeutic action for curcumin.
The layer‐by‐layer technique was successfully utilized to assembly polymer layers on a magnetic nanoparticle‐based core. The obtained nanoplatforms are magneto responsive and the magnetic hyperthermia induced by the application of an external magnetic field triggers controlled and heat‐induced release of curcumin, loaded into the polymer layers, improving its bioavailability and efficiency for further development of drug delivery systems.
Abstract
The Earth is bombarded by ultrarelativistic particles, known as cosmic rays (CRs). CRs with energies up to a few PeV (=10
15
eV), the knee in the particle spectrum, are believed to have a ...Galactic origin. One or more factories of PeV CRs, or PeVatrons, must thus be active within our Galaxy. The direct detection of PeV protons from their sources is not possible since they are deflected in the Galactic magnetic fields. Hundred TeV
γ
-rays from decaying
π
0
, produced when PeV CRs collide with the ambient gas, can provide the decisive evidence of proton acceleration up to the knee. Here we report the discovery by the High Altitude Water Cerenkov (HAWC) observatory of the
γ
-ray source, HAWC J1825-134, whose energy spectrum extends well beyond 200 TeV without a break or cutoff. The source is found to be coincident with a giant molecular cloud. The ambient gas density is as high as 700 protons cm
−3
. While the nature of this extreme accelerator remains unclear, CRs accelerated to energies of several PeV colliding with the ambient gas likely produce the observed radiation.
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