Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userInvestigating the region of 3C 397 in High Energy Gamma rays
73
0
0.0
(
0
)
Added by
Pooja Bhattacharjee
Publication date
2018
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
We investigate the supernova remnant (SNR) 3C 397 and its neighboring pulsar PSR J1906+0722 in high energy gamma rays by using nearly six years of archival data of {it Large Area Telescope} on board {it Fermi Gamma Ray Space Telescope} (Fermi-LAT). The off-pulse analysis of gamma-ray flux from the location of PSR J1906+0722 reveals an excess emission which is found to be very close to the radio location of 3C 397. Here, we present the preliminary results of this gamma-ray analysis of 3C 397 and PSR J1906+0722.
rate research
Read More
In May - July 2014, the flat spectrum radio quasar 3C 454.3 exhibited strong flaring behaviour. Observations with the Large Area Telescope detector on-board the Fermi Gamma-ray Space Telescope captured the $gamma$-ray flux at energies 0.1 $leq E_{gamma}leq$ 300 GeV increasing fivefold during this period, with two distinct peaks in emission. The $gamma$-ray emission is analysed in detail, in order to study the emission characteristics and put constraints on the location of the emission region. We explore variability in the spectral shape of 3C 454.3, search for evidence of a spectral cutoff, quantify the significance of VHE emission and investigate whether or not an energy-dependence of the emitting electron cooling exists. $gamma$-ray intrinsic doubling timescales as small as $tau_{int} = 0.68$ $pm$ 0.01 h at a significance of > 5$sigma$ are found, providing evidence of a compact emission region. Significant $E_{gamma, emitted}geq$ 35 GeV and $E_{gamma, emitted}geq$ 50 GeV emission is also observed. The location of the emission region can be constrained to $rgeq1.3$ $times$ $R_{BLR}^{out}$, a location outside the broad-line region. The spectral variation of 3C 454.3 also suggests that these flares may be originating further downstream of the supermassive black hole than the emission before and after the flares.
3C 84 (NGC 1275) is the bright radio core of the Perseus Cluster. Even in the absence of strong relativistic effects, the source has been detected at Gamma-rays up to TeV energies. Despite its intensive study, the physical processes responsible for the high-energy emission in the source remain unanswered. We present a detailed kinematics study of the source and its connection to Gamma-ray emission. The sub-parsec scale radio structure is dominated by slow-moving features in both the eastern and western lanes of the jet. The jet appears to have accelerated to its maximum speed within less than 125 000 gravitational radii. The fastest reliably detected speed in the jet was ~0.9 c. This leads to a minimum Lorentz factor of ~1.35. Our analysis suggests the presence of multiple high-energy sites in the source. If Gamma-rays are associated with kinematic changes in the jet, they are being produced in both eastern and western lanes in the jet. Three Gamma-ray flares are contemporaneous with epochs where the slowly moving emission region splits into two sub-regions. We estimate the significance of these events being associated as ~2-3 sigma. We tested our results against theoretical predictions for magnetic reconnection-induced mini-jets and turbulence and find them compatible.
The propagation of very high energy gamma-rays ($E>100$~GeV) over cosmological distances is suppressed by pair-production processes with the ubiquitous extra-galactic soft photon background, mainly in the optical to near infra-red. The detailed spectroscopy of gamma-ray emitting blazars has revealed the signature of this absorption process leading to a meaningful measurement of the background photon field which is linked to the star-forming history of the universe. Deviations from the expected absorption have been claimed in the past. Here the status of the observations is summarized, an update on the search for the persisting anomalous transparency is given and discussed.
241 -
The VERITAS Collaboration
, the VLBA 43 GHz M 87 Monitoring Team
, then H.E.S.S. Collaboration
2009
The accretion of matter onto a massive black hole is believed to feed the relativistic plasma jets found in many active galactic nuclei (AGN). Although some AGN accelerate particles to energies exceeding 10^12 electron Volts (eV) and are bright sources of very-high-energy (VHE) gamma-ray emission, it is not yet known where the VHE emission originates. Here we report on radio and VHE observations of the radio galaxy M87, revealing a period of extremely strong VHE gamma-ray flares accompanied by a strong increase of the radio flux from its nucleus. These results imply that charged particles are accelerated to very high energies in the immediate vicinity of the black hole.
We present a search of very high energy gamma-ray emission from the Northern $textit{Fermi}$ Bubble region using data collected with the High Altitude Water Cherenkov (HAWC) gamma-ray observatory. The size of the data set is 290 days. No significant excess is observed in the Northern $textit{Fermi}$ Bubble region, hence upper limits above $1,text{TeV}$ are calculated. The upper limits are between $3times 10^{-7},text{GeV}, text{cm}^{-2}, text{s}^{-1},text{sr}^{-1}$ and $4times 10^{-8},text{GeV},text{cm}^{-2},text{s}^{-1},text{sr}^{-1}$. The upper limits disfavor a proton injection spectrum that extends beyond $100,text{TeV}$ without being suppressed. They also disfavor a hadronic injection spectrum derived from neutrino measurements.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
