101 research outputs found
Search for Gamma-Ray and Neutrino Coincidences Using HAWC and ANTARES Data
In the quest for high-energy neutrino sources, the Astrophysical Multimessenger Observatory Network has implemented a new search by combining data from the High Altitude Water Cherenkov (HAWC) Observatory and the Astronomy with a Neutrino Telescope and Abyss environmental RESearch (ANTARES) neutrino telescope. Using the same analysis strategy as in a previous detector combination of HAWC and IceCube data, we perform a search for coincidences in HAWC and ANTARES events that are below the threshold for sending public alerts in each individual detector. Data were collected between 2015 July and 2020 February with a live time of 4.39 yr. Over this time period, three coincident events with an estimated false-alarm rate of <1 coincidence per year were found. This number is consistent with background expectations.The National Science Foundation under grants PHY-1708146PHY-1806854The Institute for Gravitation and the
Cosmos of the Pennsylvania State UniversityCentre National de la Recherche
Scientifique (CNRS)Commissariat à l’énergie atomique et aux
énergies alternatives (CEA)Commission Européenne (FEDER
fund and Marie Curie Program)Institut Universitaire de
France (IUF), LabEx UnivEarthS (ANR-10-LABX-0023 and
ANR-18-IDEX-0001)Région Île-de-France (DIM-ACAV),
Région Alsace (contrat CPER)Région Provence-Alpes-Côte
d’Azur, Département du Var and Ville de La Seyne-sur-MerBundesministerium für Bildung und Forschung
(BMBF)Istituto Nazionale di Fisica Nucleare
(INFN)Nederlandse organisatie voor Wetenschappelijk
Onderzoek (NWO)Executive Unit for
Financing Higher Education, ResearchDevelopment and
Innovation (UEFISCDI)Romania; Ministerio de Ciencia,
Innovación, Investigación y Universidades (MCIU)Programa
Estatal de Generación de Conocimiento (refs. PGC2018-
096663-B-C41, -A-C42-B-C43-B-C44PID2021-
124591NB-C41-C42-C43(MCIU/FEDER)Generalitat
ValencianaPrometeo (PROMETEO/2020/019)Grisolía
(refs. GRISOLIA/2018/119, /2021/192)GenT (refs.
/2019/043, /2020/049, /2021/023) programs, Junta de
Andalucía (ref. A-FQM-053-UGR18)La Caixa Foundation
(ref. LCF/BQ/IN17/11620019)MSC program (ref.
101025085)Spain; Ministry of Higher Education, Scientific
Research and InnovationThe Arab Fund for
Economic and Social Development, KuwaitUS National
Science Foundation (NSF)The US Department of Energy
Office of High-Energy PhysicsLaboratory Directed
Research and Development (LDRD) program of Los Alamos
National LaboratoryConsejo Nacional de Ciencia y Tecnología
(CONACyT)México, grants 271051, 232656, 260378179588254964258865243290132197A1-S-46288A1-
S-22784Cátedras 873, 1563, 341, 323Red HAWC, MéxicoDGAPA-UNAM grants IG101320IN111716-3, IN111419IA102019IN110621IN110521VIEP-BUAPPIFI 2012PROFOCIE 2014, 2015the University of Wisconsin
Alumni Research FoundationThe Institute of Geophysics,
Planetary PhysicsSignatures at Los Alamos National LaboratoryPolish Science Centre grantDEC-2017/27/B/
ST9/02272Coordinación de la Investigación Científica de la
Universidad Michoacana; Royal Society—Newton Advanced
Fellowship 180385Generalitat Valenciana, grant CIDEGENT/
2018/034The Program Management Unit for Human
Resources & Institutional Development, Research and Innovation,
NXPO (grant No. B16F630069)Coordinación General
Académica e Innovación (CGAI-UdeG)PRODEP-SEP UDGCA-
499; Institute of Cosmic Ray Research (ICRR),University
of TokyoNASA under award
number 80GSFC21M000
Multiwavelength follow-up of a rare IceCube neutrino multiplet
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 coming from the same point in the sky. Such a triplet is expected once every 13.7 years as a random coincidence of
background events. However, considering the lifetime of the follow-up program the probability of detecting at least one triplet from atmospheric
background is 32%. Follow-up observatories were notified in order to search for an electromagnetic counterpart. Observations were obtained by
Swift
’s X-ray telescope, by ASAS-SN, LCO and MASTER at optical wavelengths, and by VERITAS in the very-high-energy gamma-ray regime.
Moreover, the
Swift
BAT serendipitously observed the location 100 s after the first neutrino was detected, and data from the
Fermi
LAT and HAWC
observatory were analyzed. We present details of the neutrino triplet and the follow-up observations. No likely electromagnetic counterpart was
detected, and we discuss the implications of these constraints on candidate neutrino sources such as gamma-ray bursts, core-collapse supernovae
and active galactic nucleus flares. This study illustrates the potential of and challenges for future follow-up campaign
The real interest rate differential : international evidence based on nonlinear unit root tests
This paper aims at testing international parity conditions by using nonlinear unit root tests
advocated by Kapetanios et al. (2003, KSS). Results from the KSS tests based on 17 countries (G7 and 10 Asian countries) overwhelmingly show that the adjustment of real interest rates towards the RIP follows a nonlinear process except for the Malaysian relationships with both the US and Japan. Overall, the empirical results are in favor of RIP using the US and Japan as the center countries but only if nonlinearities are accounted for in the data generating process. Our findings confirm that interest rate differentials, like the real exchange rates reported in recent literature, display a nonlinear
mean reversion process
First Study of Combined Blazar Light Curves with FACT and HAWC
For studying variable sources like blazars, it is crucial to achieve unbiased
monitoring, either with dedicated telescopes in pointing mode or survey
instruments. At TeV energies, the High Altitude Water Cherenkov (HAWC)
observatory monitors approximately two thirds of the sky every day. It uses the
water Cherenkov technique, which provides an excellent duty cycle independent
of weather and season. The First G-APD Cherenkov Telescope (FACT) monitors a
small sample of sources with better sensitivity, using the imaging air
Cherenkov technique. Thanks to its camera with silicon-based photosensors, FACT
features an excellent detector performance and stability and extends its
observations to times with strong moonlight, increasing the duty cycle compared
to other imaging air Cherenkov telescopes. As FACT and HAWC have overlapping
energy ranges, a joint study can exploit the longer daily coverage given that
the observatories' locations are offset by 5.3 hours. Furthermore, the better
sensitivity of FACT adds a finer resolution of features on hour-long time
scales, while the continuous duty cycle of HAWC ensures evenly sampled
long-term coverage. Thus, the two instruments complement each other to provide
a more complete picture of blazar variability. In this presentation, the first
joint study of light curves from the two instruments will be shown, correlating
long-term measurements with daily sampling between air and water Cherenkov
telescopes. The presented results focus on the study of the variability of the
bright blazars Mrk 421 and Mrk 501 during the last two years featuring various
flaring activities.Comment: 6 pages, 2 figures. Contribution to the 6th International Symposium
on High Energy Gamma-Ray Astronomy (Gamma2016), Heidelberg, Germany. To be
published in the AIP Conference Proceeding
Gamma Ray Bursts: recent results and connections to very high energy Cosmic Rays and Neutrinos
Gamma-ray bursts are the most concentrated explosions in the Universe. They
have been detected electromagnetically at energies up to tens of GeV, and it is
suspected that they could be active at least up to TeV energies. It is also
speculated that they could emit cosmic rays and neutrinos at energies reaching
up to the eV range. Here we review the recent developments in
the photon phenomenology in the light of \swift and \fermi satellite
observations, as well as recent IceCube upper limits on their neutrino
luminosity. We discuss some of the theoretical models developed to explain
these observations and their possible contribution to a very high energy cosmic
ray and neutrino background.Comment: 12 pages, 7 figures. Text of a plenary lecture at the PASCOS 12
conference, Merida, Yucatan, Mexico, June 2012; to appear in J.Phys. (Conf.
Series
Daily monitoring of TeV gamma-ray emission from Mrk 421, Mrk 501, and the Crab Nebula with HAWC
We present results from daily monitoring of gamma rays in the energy range
to TeV with the first 17 months of data from the High
Altitude Water Cherenkov (HAWC) Observatory. Its wide field of view of 2
steradians and duty cycle of % are unique features compared to other TeV
observatories that allow us to observe every source that transits over HAWC for
up to hours each sidereal day. This regular sampling yields
unprecedented light curves from unbiased measurements that are independent of
seasons or weather conditions. For the Crab Nebula as a reference source we
find no variability in the TeV band. Our main focus is the study of the TeV
blazars Markarian (Mrk) 421 and Mrk 501. A spectral fit for Mrk 421 yields a
power law index and
an exponential cut-off
TeV. For Mrk 501, we find an index and exponential cut-off TeV. The light curves for both sources show clear
variability and a Bayesian analysis is applied to identify changes between flux
states. The highest per-transit fluxes observed from Mrk 421 exceed the Crab
Nebula flux by a factor of approximately five. For Mrk 501, several transits
show fluxes in excess of three times the Crab Nebula flux. In a comparison to
lower energy gamma-ray and X-ray monitoring data with comparable sampling we
cannot identify clear counterparts for the most significant flaring features
observed by HAWC.Comment: 18 pages, 10 figures, accepted for publication in The Astrophysical
Journa
Observation of the Crab Nebula with the HAWC Gamma-Ray Observatory
The Crab Nebula is the brightest TeV gamma-ray source in the sky and has been
used for the past 25 years as a reference source in TeV astronomy, for
calibration and verification of new TeV instruments. The High Altitude Water
Cherenkov Observatory (HAWC), completed in early 2015, has been used to observe
the Crab Nebula at high significance across nearly the full spectrum of
energies to which HAWC is sensitive. HAWC is unique for its wide field-of-view,
nearly 2 sr at any instant, and its high-energy reach, up to 100 TeV. HAWC's
sensitivity improves with the gamma-ray energy. Above 1 TeV the
sensitivity is driven by the best background rejection and angular resolution
ever achieved for a wide-field ground array.
We present a time-integrated analysis of the Crab using 507 live days of HAWC
data from 2014 November to 2016 June. The spectrum of the Crab is fit to a
function of the form . The data is well-fit with values of
, , and
log when
is fixed at 7 TeV and the fit applies between 1 and 37 TeV. Study of the
systematic errors in this HAWC measurement is discussed and estimated to be
50\% in the photon flux between 1 and 37 TeV.
Confirmation of the Crab flux serves to establish the HAWC instrument's
sensitivity for surveys of the sky. The HAWC survey will exceed sensitivity of
current-generation observatories and open a new view of 2/3 of the sky above 10
TeV.Comment: Submitted 2017/01/06 to the Astrophysical Journa
All-particle cosmic ray energy spectrum measured by the HAWC experiment from 10 to 500 TeV
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 ground based air-shower array deployed on the slopes
of Volcan Sierra Negra in the state of Puebla, Mexico, and is sensitive to
gamma rays and cosmic rays at TeV energies. The data used in this work were
taken from 234 days between June 2016 to February 2017. The primary cosmic-ray
energy is determined with a maximum likelihood approach using the particle
density as a function of distance to the shower core. Introducing quality cuts
to isolate events with shower cores landing on the array, the reconstructed
energy distribution is unfolded iteratively. The measured all-particle spectrum
is consistent with a broken power law with an index of prior to
a break at ) TeV, followed by an index of . The
spectrum also respresents a single measurement that spans the energy range
between direct detection and ground based experiments. As a verification of the
detector response, the energy scale and angular resolution are validated by
observation of the cosmic ray Moon shadow's dependence on energy.Comment: 16 pages, 11 figures, 4 tables, submission to Physical Review
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