scholarly journals Search for γ-ray emission from superluminous supernovae with the Fermi-LAT

2018 ◽  
Vol 611 ◽  
pp. A45 ◽  
Author(s):  
N. Renault-Tinacci ◽  
K. Kotera ◽  
A. Neronov ◽  
S. Ando
Keyword(s):  
Neutron Stars ◽  
Confidence Level ◽  
Compact Object ◽  
Photon Spectrum ◽  
Systematic Search ◽  
Large Area ◽  
Rotation Periods ◽  
Upper Limit ◽  
Upper Limits ◽  
Γ Ray

We present the first individual and stacking systematic search for γ-ray emission in the GeV band in the directions of 45 superluminous supernovae (SLSNe) with the Fermi Large Area Telescope (LAT). No excess of γ-rays from the SLSN positions was found. We report γ-ray luminosity upper limits and discuss the implication of these results on the origin of SLSNe and, in particular, the scenario of central compact object-aided SNe. From the stacking search, we derived an upper limit at 95% confidence level to the γ-ray luminosity (above 600 MeV) Lγ < 9.1 × 1041 erg s−1 for an assumed E−2 photon spectrum for our full SLSN sample. We conclude that the rate of the neutron stars born with millisecond rotation periods P ≲ 2 ms and B ~ 1012−13 G must be lower than the rate of the observed SLSNe. The luminosity limits obtained on individual sources are also constraining: in particular, SN2013fc, CSS140222, SN2010kd, and PTF12dam can only be born with millisecond periods if B ≲ 1013 G.

scholarly journals Very high energy γ-ray emission from two blazars of unknown redshift and upper limits on their distance

2020 ◽  
Vol 494 (4) ◽  
pp. 5590-5602
Author(s):  
H Abdalla ◽  
R Adam ◽  
F Aharonian ◽  
F Ait Benkhali ◽  
E O Angüner ◽  
...  
Keyword(s):  
Confidence Level ◽  
High Energy ◽  
Bl Lac Objects ◽  
Upper Limit ◽  
Upper Limits ◽  
Bl Lac ◽  
Very High Energy ◽  
Stereoscopic System ◽  
Γ Ray ◽  
Very High

ABSTRACT We report on the detection of very high energy (VHE; E &gt; 100 GeV) γ-ray emission from the BL Lac objects KUV 00311−1938 and PKS 1440−389 with the High Energy Stereoscopic System (H.E.S.S.). H.E.S.S. observations were accompanied or preceded by multiwavelength observations with Fermi/LAT, XRT and UVOT onboard the Swift satellite, and ATOM. Based on an extrapolation of the Fermi/LAT spectrum towards the VHE γ-ray regime, we deduce a 95 per cent confidence level upper limit on the unknown redshift of KUV 00311−1938 of $z$ &lt; 0.98 and of PKS 1440−389 of $z$ &lt; 0.53. When combined with previous spectroscopy results, the redshift of KUV 00311−1938 is constrained to 0.51 ≤ $z$ &lt; 0.98 and of PKS 1440−389 to 0.14 ⪅ $z$ &lt; 0.53.

scholarly journals Search for π0 decays to invisible particles

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
E. Cortina Gil ◽  
◽  
A. Kleimenova ◽  
E. Minucci ◽  
S. Padolski ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Confidence Level ◽  
Branching Ratio ◽  
Standard Model Higgs Boson ◽  
Scalar Mixing ◽  
Upper Limit ◽  
Upper Limits ◽  
The Standard Model ◽  
Model Independent

Abstract The NA62 experiment at the CERN SPS reports a study of a sample of 4 × 109 tagged π0 mesons from K+ → π+π0(γ), searching for the decay of the π0 to invisible particles. No signal is observed in excess of the expected background fluctuations. An upper limit of 4.4 × 10−9 is set on the branching ratio at 90% confidence level, improving on previous results by a factor of 60. This result can also be interpreted as a model- independent upper limit on the branching ratio for the decay K+ → π+X, where X is a particle escaping detection with mass in the range 0.110–0.155 GeV/c2 and rest lifetime greater than 100 ps. Model-dependent upper limits are obtained assuming X to be an axion-like particle with dominant fermion couplings or a dark scalar mixing with the Standard Model Higgs boson.

scholarly journals Systematic Search for γ-Ray Periodicity in Active Galactic Nuclei Detected by the Fermi Large Area Telescope

2020 ◽  
Vol 896 (2) ◽  
pp. 134 ◽  
Author(s):  
P. Peñil ◽  
A. Domínguez ◽  
S. Buson ◽  
M. Ajello ◽  
J. Otero-Santos ◽  
...  
Keyword(s):  
Active Galactic Nuclei ◽  
Galactic Nuclei ◽  
Systematic Search ◽  
Large Area ◽  
Γ Ray

scholarly journals Small-Scale Structure Deduced from X- and γ-ray Timing Measurements

2001 ◽  
Vol 205 ◽  
pp. 244-251
Author(s):  
M. Coleman Miller
Keyword(s):  
Black Holes ◽  
Neutron Stars ◽  
Small Scale ◽  
Large Area ◽  
X Ray ◽  
Strong Gravity ◽  
Thermonuclear Burning ◽  
General Relativistic ◽  
Γ Ray ◽  
Area X

X-ray timing observations of neutron stars and black holes are among the few available probes of ultrastrong magnetic fields, strong gravity, high densities, and the propagation of thermonuclear burning. Here we review the evidence for these effects revealed with data from the Rossi Explorer in the last five years. We also discuss the exciting prospects for making the first quantitative tests of strong-gravity general relativistic predictions with a large-area X-ray timing mission.

scholarly journals RESULTS FROM THE BINARIES LS I +61°303 and LS 5039 AFTER 2.5 YEARS OF FERMI MONITORING

2012 ◽  
Vol 08 ◽  
pp. 61-66 ◽  
Author(s):  
◽  
DANIELA HADASCH
Keyword(s):  
Orbital Period ◽  
Orbital Motion ◽  
First Year ◽  
Large Area ◽  
Spectral Evolution ◽  
Positional Uncertainty ◽  
Steady Decrease ◽  
Upper Limits ◽  
Γ Ray

The Fermi Large Area Telescope (LAT) made the first definitive GeV detections of the binaries LS I +61°303 and LS 5039 in the first year after its launch in August 2008. These detections were unambiguous because, apart from a reduced positional uncertainty, the γ-ray emission in each case was orbitally modulated with the corresponding orbital period. The LAT results posed new questions about the nature of these objects, after the unexpected observation of an exponential cutoff in the GeV γ-ray spectra of both LS I +61°303 and LS 5039, at least along part of their orbital motion. We present here the analysis of new data from the LAT, comprising 2.5 years of observations through which LS I +61°303 continues to provide some surprises. We find an increase in flux in March 2009 and a steady decrease in the flux fraction modulation. The LAT now detects emission up to 30 GeV, where prior datasets led to upper limits only. At the same time, contemporaneous TeV observations either no longer detected the source, or found it -at least in some orbits- close to periastron, far from the usual phases in which the source usually appeared at TeV energies. The on-source exposure of LS 5039 has also drastically increased along the last years, and whilst our analysis shows no new behavior in comparison with our earlier report, the higher statistics of the current dataset allows for a deeper investigation of its orbital and spectral evolution.

scholarly journals X-ray and γ-ray orbital variability from the γ-ray binary HESS J1832−093

2020 ◽  
Vol 637 ◽  
pp. A23 ◽  
Author(s):  
G. Martí-Devesa ◽  
O. Reimer
Keyword(s):  
Energy Distribution ◽  
Massive Star ◽  
Spectral Energy Distribution ◽  
Compact Object ◽  
Spectral Energy ◽  
Large Area ◽  
Optical Telescope ◽  
X Ray ◽  
Orbital Modulation ◽  
Γ Ray

Context.γ-ray binaries are systems composed of a massive star and a compact object whose interaction leads to particle acceleration up to relativistic energies. In the last fifteen years, a few binaries have been found to emit at high energies, but their number is still low. The TeV source HESS J1832−093 has been proposed as a binary candidate, although its nature is unclear. Neither a GeV counterpart nor a period was detected. Aims. The purpose of this work is to search for a GeV counterpart to understand the origin of the TeV signal detected by H.E.S.S. For an unambiguous identification of its binary nature, finding an orbital modulation is crucial. Methods. We analysed data spanning more than 10 years from the Fermi Large Area Telescope (Fermi-LAT), together with Swift archival observations taken between 2015 and 2018, using both the X-Ray Telescope and UV/Optical Telescope. We searched for periodicities in both X-ray and GeV bands. Results. We find a periodic modulation of ∼ 86 days in the X-ray source candidate counterpart XMMU J183245−0921539, together with indications of γ-ray modulation with a compatible period in the GeV candidate counterpart 4FGL J1832.9−0913. Neither an optical nor a UV counterpart is found at the X-ray source location. The overall spectral energy distribution strongly resembles the known γ-ray binary HESS J0632+057. Conclusions. Both the spectral energy distribution and the discovery of an orbital period allow the identification of the TeV source HESS J1832−093 as a new member of the γ-ray binary class.

New Results from Single-Top-Quark Searches with the CDF II Detector

2005 ◽  
Vol 20 (14) ◽  
pp. 3193-3196
Author(s):  
◽  
CATALIN I. CIOBANU
Keyword(s):  
Production Rate ◽  
Top Quark ◽  
Confidence Level ◽  
Proton Antiproton ◽  
Significant Evidence ◽  
Upper Limit ◽  
Single Top ◽  
Upper Limits ◽  
Cdf Ii ◽  
The Individual

In this paper we present new results from single-top-quark searches with the CDF II detector at the Fermilab Tevatron. In a data sample of 162 pb-1 of proton-antiproton collisions accumulated at CDF, we find no significant evidence for signal and set an upper limit of 17.8 pb on the total single-top production rate, at 95% confidence level. Individual upper limits of 10.1 pb and 13.6 pb are set on the the individual rates of t–channel, and s–channel single-top, respectively.

Search for Bc and ϒ in Hadronic Z Decays

1997 ◽  
Vol 12 (22) ◽  
pp. 3921-3930 ◽  
Author(s):  
M. McNeil
Keyword(s):  
Confidence Level ◽  
Branching Fraction ◽  
Mass Window ◽  
Upper Limit ◽  
Independent Analysis ◽  
Upper Limits ◽  
Aleph Detector ◽  
Z Decays ◽  
Hadronic Z Decays ◽  
Background Events

Out of 3.9 million hadronic Z decays collected by the ALEPH detector, a sample of approximately 700 J/ψ events decaying into e+ e- or μ+μ- are selected. A search for the Bc meson decaying into the channels J/ψπ+, J/ψe+νe and J/ψμ+νμ is then performed, resulting in the observation of 0, 1 and 1 candidate in each of these channels respectively, with 0.37, 0.28 and 0.36 background events expected. The following 90% confidence level upper limits are derived: [Formula: see text] An intriguing candidate, found in an independent analysis, is also described in detail. Using the same data sample, a search is performed for the ϒ(1S), ϒ(2S) and ϒ(3S) states, decaying into either e+e- or μ+μ-. After kinematic and topological cuts a total of 1.2 ± 0.4 background events are expected for both channels in the mass window chosen. Two events are observed, allowing the following 90% confidence level branching fraction upper limit to be derived: [Formula: see text]

scholarly journals A search for γ-ray emission from a sample of local Universe low-frequency selected radio galaxies

2020 ◽  
Vol 496 (1) ◽  
pp. 903-912
Author(s):  
Max Harvey ◽  
Cameron B Rulten ◽  
Paula M Chadwick
Keyword(s):  
Low Frequency ◽  
Radio Galaxies ◽  
Large Area ◽  
Complete Sample ◽  
Local Universe ◽  
The Earth ◽  
Upper Limits ◽  
Γ Ray ◽  
The Look ◽  
Large Parameter Space

ABSTRACT Radio galaxies are uncommon γ-ray emitters, and only low-redshift radio galaxies are detected with the Fermi Large Area Telescope (Fermi-LAT). However, they offer potential insights into the emission mechanisms of active galaxies, particularly as the alignment of their jets with respect to the Earth means that, unlike blazars, their emission is not necessarily jet dominated. We use the Fermi-LAT data to perform an unbiased survey of 78 radio galaxies from the Bologna complete sample in order to search for new γ-ray-emitting radio galaxies. We observe statistically significant γ-ray emission from four of the six known Fermi-LAT-detected radio galaxies included in this sample, and find some evidence for γ-ray emission spatially coincident with four previously undetected radio galaxies. As a large parameter space is searched, we calculate a probability distribution to compute the look-elsewhere effect. We find that these four spatially coincident sub-threshold γ-ray excesses are most likely a chance association, and are unlikely to be emission from the radio galaxies. Upper limits on flux are calculated for the radio galaxies from which no γ-ray emission is observed.

Vitamin-A-Exzess durch Pferdefleischprodukte mit hohen Leberanteilen

2013 ◽  
Vol 41 (01) ◽  
pp. 31-36
Author(s):  
E. Kienzle ◽  
N. Becker
Keyword(s):  
Vitamin A ◽  
Eine Analyse ◽  
Upper Limit ◽  
Upper Limits

ZusammenfassungIm Rahmen einer Eliminationsdiät wird regelmäßig Pferdefleisch eingesetzt. Aus Gründen der Praktikabilität verwenden Tierbesitzer häufig kommerziell erhältliches Pferdefleisch aus der Dose. Aufgrund eines Berichts von Zervikalspondylosen bei einer auf Futtermittel allergischen Katze erfolgte eine Analyse verschiedener auf Pferdefleisch basierender Produkte hinsichtlich des Vitamin-AGehalts.In 14 Pferdefleischerzeugnissen wurde der Vitamin-A-Gehalt (Retinol) analysiert. Der Gehalt an umsetzbarer Energie wurde mithilfe von Schätzformeln auf Basis der Deklaration berechnet.In Produkten mit deklarierten Anteilen von Leber, Innereien oder tierischen Nebenprodukten konnten zum Teil erhebliche Vitamin-A-Gehalte festgestellt werden. Bei alleiniger Verfütterung eines dieser Produkte (Deckung des durchschnittlichen Energiebedarfs) würde die Vitamin-A-Versorgung nur knapp unter dem Safe Upper Limit der Katze sowie oberhalb des Safe Upper Limits beim Hund liegen.Bei All-Meat-Produkten sollte nicht nur die Deklaration, sondern auch der Inhalt näher betrachtet werden, um einen Hinweis auf eventuell hohe Leberanteile zu erhalten.Aufgrund der Ergebnisse ist eine exzessive Vitamin-A-Aufnahme bei langfristiger Verfütterung von Pferdefleischprodukten mit hohen Leberanteilen nicht auszuschließen.

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