2,232 research outputs found
Tentative evidence of spatially extended GeV emission from SS433/W50
We analyze 10 years of Fermi-LAT data towards the SS433/W50 region. With the
latest source catalog and diffuse background models, the gamma-ray excess from
SS433/W50 is detected with a significance of 6{\sigma} in the photon energy
range of 500 MeV - 10 GeV. Our analysis indicates that an extended flat disk
morphology is preferred over a point-source description, suggesting that the
GeV emission region is much larger than that of the TeV emission detected by
HAWC. The size of the GeV emission is instead consistent with the extent of the
radio nebula W50, a supernova remnant being distorted by the jets, so we
suggest that the GeV emission may originate from this supernova remnant. The
spectral result of the GeV emission is also consistent with an supernova
remnant origin. We also derive the GeV flux upper limits on the TeV emission
region, which put moderate constrains on the leptonic models to explain the
multiwavelength data.Comment: 7 pages, 4 figures, accepted for publication in A&
Detection of gamma-ray emission from the Coma cluster with Fermi Large Area Telescope and tentative evidence for an extended spatial structure
Many galaxy clusters have giant halos of non-thermal radio emission,
indicating the presence of relativistic electrons in the clusters. Relativistic
protons may also be accelerated by merger and/or accretion shocks in galaxy
clusters. These cosmic-ray (CR) electrons and/or protons are expected to
produce gamma-rays through inverse-Compton scatterings or inelastic
collisions respectively. Despite of intense efforts in searching for
high-energy gamma-ray emission from galaxy clusters, conclusive evidence is
still missing so far. Here we report the discovery of MeV gamma-ray
emission from the Coma cluster direction with an unbinned likelihood analysis
of the 9 years of {\it Fermi}-LAT Pass 8 data. The gamma-ray emission shows a
spatial morphology roughly coincident with the giant radio halo, with an
apparent excess at the southwest of the cluster. Using the test statistic
analysis, we further find tentative evidence that the gamma-ray emission at the
Coma center is spatially extended. The extended component has an integral
energy flux of in the
energy range of 0.2 - 300 GeV and the spectrum is soft with a photon index of
. Interpreting the gamma-ray emission as arising from CR proton
interaction, we find that the volume-averaged value of the CR to thermal
pressure ratio in the Coma cluster is about . Our results show that
galaxy clusters are likely a new type of GeV gamma-ray sources, and they are
probably also giant reservoirs of CR protons.Comment: 10 pages, 10 figures, Accepted by Physical Review D, more spatial
models for the gamma-ray emission are used, systematic checks on the results
are adde
Diff-Transfer: Model-based Robotic Manipulation Skill Transfer via Differentiable Physics Simulation
The capability to transfer mastered skills to accomplish a range of similar
yet novel tasks is crucial for intelligent robots. In this work, we introduce
, a novel framework leveraging differentiable physics
simulation to efficiently transfer robotic skills. Specifically,
discovers a feasible path within the task space that
brings the source task to the target task. At each pair of adjacent points
along this task path, which is two sub-tasks, adapts
known actions from one sub-task to tackle the other sub-task successfully. The
adaptation is guided by the gradient information from differentiable physics
simulations. We propose a novel path-planning method to generate sub-tasks,
leveraging -learning with a task-level state and reward. We implement our
framework in simulation experiments and execute four challenging transfer tasks
on robotic manipulation, demonstrating the efficacy of
through comprehensive experiments. Supplementary and Videos are on the website
https://sites.google.com/view/difftransfe
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