Search results for "Crab nebula"
showing 10 items of 12 documents
IceCube Search for High-Energy Neutrino Emission from TeV Pulsar Wind Nebulae
2020
Pulsar wind nebulae (PWNe) are the main gamma-ray emitters in the Galactic plane. They are diffuse nebulae that emit nonthermal radiation. Pulsar winds, relativistic magnetized outflows from the central star, shocked in the ambient medium produce a multiwavelength emission from the radio through gamma-rays. Although the leptonic scenario is able to explain most PWNe emission, a hadronic contribution cannot be excluded. A possible hadronic contribution to the high-energy gamma-ray emission inevitably leads to the production of neutrinos. Using 9.5 yr of all-sky IceCube data, we report results from a stacking analysis to search for neutrino emission from 35 PWNe that are high-energy gamma-ray…
OBSERVATION OF THE TeV GAMMA-RAY SOURCE MGRO J1908+06 WITH ARGO-YBJ
2012
The extended gamma ray source MGRO J1908+06, discovered by the Milagro air shower detector in 2007, has been observed for about 4 years by the ARGO-YBJ experiment at TeV energies, with a statistical significance of 6.2 standard deviations. The peak of the signal is found at a position consistent with the pulsar PSR J1907+0602. Parametrizing the source shape with a two-dimensional Gauss function we estimate an extension \sigma = 0.49 \pm 0.22 degrees, consistent with a previous measurement by the Cherenkov Array H.E.S.S.. The observed energy spectrum is dN/dE = 6.1 \pm 1.4 \times 10^-13 (E/4 TeV)^{-2.54 \pm 0.36} photons cm^-2 s^-1 TeV^-1, in the energy range 1-20 TeV. The measured gamma ray…
Gamma-Ray Flares from Mrk421 in 2008 observed with the ARGO-YBJ detector
2010
In 2008 the blazar Markarian 421 entered a very active phase and was one of the brightest sources in the sky at TeV energies, showing frequent flaring episodes. Using the data of ARGO-YBJ, a full coverage air shower detector located at Yangbajing (4300 m a.s.l., Tibet, China), we monitored the source at gamma ray energies E > 0.3 TeV during the whole year. The observed flux was variable, with the strongest flares in March and June, in correlation with X-ray enhanced activity. While during specific episodes the TeV flux could be several times larger than the Crab Nebula one, the average emission from day 41 to 180 was almost twice the Crab level, with an integral flux of (3.6 +-0.6) 10^-1…
Observation of TeV gamma rays from the Cygnus region with the ARGO-YBJ experiment
2012
We report the observation of TeV gamma-rays from the Cygnus region using the ARGO-YBJ data collected from 2007 November to 2011 August. Several TeV sources are located in this region including the two bright extended MGRO J2019+37 and MGRO J2031+41. According to the Milagro data set, at 20 TeV MGRO J2019+37 is the most significant source apart from the Crab Nebula. No signal from MGRO J2019+37 is detected by the ARGO-YBJ experiment, and the derived flux upper limits at 90% confidence level for all the events above 600 GeV with medium energy of 3 TeV are lower than the Milagro flux, implying that the source might be variable and hard to be identified as a pulsar wind nebula. The only statist…
Highlights from the ARGO-YBJ Experiment
2012
""The ARGO-YBJ experiment at YangBaJing in Tibet (4300m a.s.l.) has been taking data with its full layout since October 2007. Here we present a few significant results obtained in gamma-ray astronomy and cosmic-ray physics. Emphasis is placed on the analysis of gamma-ray emission from point-like sources (Crab Nebula, MRK 421), on the preliminary limit on the antiproton\\\/proton flux ratio, on the large-scale cosmic-ray anisotropy and on the proton-air cross-section. The performance of the detector is also discussed, and the perspectives of the experiment are outlined.""
Bepposax: 3 Years of Operation
2001
BeppoSAX, the X-Ray Astronomy satellite operating in the (0.1–300) keY energy band has now lived more than 30.000 hours in orbit and it is halfway to complete the 3rd round of observations (A03 started at the beginning of may 1999 and it will end in April 2000). A report is given on the general fields covered by the mission and on the more relevant results obtained. The satellite is in excellent operating conditions and it is foreseen to continue the observational life-time well beyond the initially scheduled 3 years.
Synchrotron Radiation from the Crab Nebula Discriminates between Models of Space-Time Foam
2003
It has been argued by Jacobson, Liberati and Mattingly that synchrotron radiation from the Crab Nebula imposes a stringent constraint on any modification of the dispersion relations of the electron that might be induced by quantum gravity. We supplement their analysis by deriving the spectrum of synchrotron radiation from the coupling of an electrically-charged particle to an external magnetic fields in the presence of quantum-gravity effects of the general form $(E/M_{QG})^\alpha$. We find that the synchrotron constraint from the Crab Nebula practically excludes $\alpha \lsim 1.74$ for $M_{QG} \sim m_P = 1.2 \times 10^{19}$ GeV. On the other hand, this analysis does not constrain any modif…
Possible pulsed gamma ray emission above 50 MeV from the Crab pulsar.
1970
A SEARCH for pulsed gamma ray emission from NP 0532 has been carried out with a balloon-borne experiment using a spark chamber as the central detector. This pulsar, situated in the Crab Nebula, is already known to pulsate in the radio, optical and X-ray range1–5.
Gamma ray sources observation with the ARGO-YBJ detector
2011
In this paper we report on the observations of TeV gamma ray sources performed by the air shower de- tector ARGO-YBJ. The objects studied in this work are the blazar Markarian 421 and the extended galactic source MGROJ1908+06, monitored during 2 years of operation. Mrk421 has been detected by ARGO-YBJ with a statisti- cal significance of 11 standard deviations. The observed TeV emission was highly variable, showing large enhance- ments of the flux during active periods. The study of the spectral behaviour during flares revealed a positive correla- tion of the hardness with the flux, as already reported in the past by the Whipple telescope, suggesting that this is a long term property of the…
In-Flight Calibrations of UFFO-Pathfinder
2013
The Ultra-Fast Flash Observatory (UFFO), which will be launched onboard the Lomonosov spacecraft, contains two crucial instruments: UFFO Burst Alert & Trigger Telescope (UBAT) for detection and localization of Gamma-Ray Bursts (GRBs) and the fast-response Slewing Mirror Telescope (SMT) designed for the observation of the prompt optical/UV counterparts. Here we discuss the in-space calibrations of the UBAT detector and SMT telescope. After the launch, the observations of the standard X-ray sources such as pulsar in Crab nebula will provide data for necessary calibrations of UBAT. Several standard stars will be used for the photometric calibration of SMT. The celestial X-ray sources, e.g.…