17 research outputs found
Multi-messenger observations of a binary neutron star merger
On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta
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The HAWC Gamma-Ray Observatory: Sensitivity to Steady and Transient Sources of Gamma Rays
The High-Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory is designed to
record air showers produced by cosmic rays and gamma rays between 100 GeV and
100 TeV. Because of its large field of view and high livetime, HAWC is
well-suited to measure gamma rays from extended sources, diffuse emission, and
transient sources. We describe the sensitivity of HAWC to emission from the
extended Cygnus region as well as other types of galactic diffuse emission;
searches for flares from gamma-ray bursts and active galactic nuclei; and the
first measurement of the Crab Nebula with HAWC-30
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The HAWC Gamma-Ray Observatory: Observations of Cosmic Rays
We describe measurements of GeV and TeV cosmic rays with the High-Altitude
Water Cherenkov Gamma-Ray Observatory, or HAWC. The measurements include the
observation of the shadow of the moon; the observation of small-scale and
large-scale angular clustering of the TeV cosmic rays; the prospects for
measurement of transient solar events with HAWC; and the observation of Forbush
decreases with the HAWC engineering array and HAWC-30
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The HAWC Gamma-Ray Observatory: Design, Calibration, and Operation
The High-Altitude Water Cherenkov Gamma Ray Observatory (HAWC) is under
construction 4100 meters above sea level at Sierra Negra, Mexico. We describe
the design and cabling of the detector, the characterization of the
photomultipliers, and the timing calibration system. We also outline a
next-generation detector based on the water Cherenkov technique
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The HAWC Gamma-Ray Observatory: Observations of Cosmic Rays
We describe measurements of GeV and TeV cosmic rays with the High-Altitude
Water Cherenkov Gamma-Ray Observatory, or HAWC. The measurements include the
observation of the shadow of the moon; the observation of small-scale and
large-scale angular clustering of the TeV cosmic rays; the prospects for
measurement of transient solar events with HAWC; and the observation of Forbush
decreases with the HAWC engineering array and HAWC-30
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Sensitivity of HAWC to high-mass dark matter annihilations
The High Altitude Water Cherenkov (HAWC) observatory is a wide field-of-view detector sensitive to gamma rays of 100 GeV to a few hundred TeV. Located in central Mexico at 19° North latitude and 4100 m above sea level, HAWC will observe gamma rays and cosmic rays with an array of water Cherenkov detectors. The full HAWC array is scheduled to be operational in Spring 2015. In this paper, we study the HAWC sensitivity to the gamma-ray signatures of high-mass (multi-TeV) dark matter annihilation. The HAWC observatory will be sensitive to diverse searches for dark matter annihilation, including annihilation from extended dark matter sources, the diffuse gamma-ray emission from dark matter annihilation, and gamma-ray emission from nonluminous dark matter subhalos. Here we consider the HAWC sensitivity to a subset of these sources, including dwarf galaxies, the M31 galaxy, the Virgo cluster, and the Galactic center. We simulate the HAWC response to gamma rays from these sources in several well-motivated dark matter annihilation channels. If no gamma-ray excess is observed, we show the limits HAWC can place on the dark matter cross section from these sources. In particular, in the case of dark matter annihilation into gauge bosons, HAWC will be able to detect a narrow range of dark matter masses to cross sections below thermal. HAWC should also be sensitive to nonthermal cross sections for masses up to nearly 1000 TeV. The constraints placed by HAWC on the dark matter cross section from known sources should be competitive with current limits in the mass range where HAWC has similar sensitivity. HAWC can additionally explore higher dark matter masses than are currently constrained