4,398 research outputs found
The likely Fermi Detection of the Supernova Remnant RCW 103
We report on the results from our -ray analysis of the supernova
remnant (SNR) RCW 103 region. The data were taken with the Large Area Telescope
on board the Fermi Gamma-ray Space Telescope. An extended source is found at a
position consistent with that of RCW 103, and its emission was only detected
above 1 GeV (10 significance), having a power-law spectrum with a
photon index of 2.00.1. We obtain its 1--300 GeV spectrum, and the total
flux gives a luminosity of 8.3 erg s at a source
distance of 3.3 kpc. Given the positional coincidence and property similarities
of this source with other SNRs, we identify it as the likely Fermi -ray
counterpart to RCW 103. Including radio measurements of RCW 103, the spectral
energy distribution (SED) is modeled by considering emission mechanisms based
on both hadronic and leptonic scenarios. We find that models in the two
scenarios can reproduce the observed SED, while in the hadronic scenario the
existence of SNR--molecular-cloud interaction is suggested as a high density of
the target protons is required.Comment: 6 pages, 3 figures, accepted for publication in Ap
Error estimates of mixed finite element methods for quadratic optimal control problems
AbstractIn this paper, we investigate the error estimates for the solutions of optimal control problems by mixed finite element methods. The state and costate are approximated by Raviart–Thomas mixed finite element spaces of order k and the control is approximated by piecewise polynomials of order k. Under the special constraint set, we will show that the control variable can be smooth in the whole domain. We derive error estimates of optimal order both for the state variables and the control variable
GeV {\gamma}-ray Emission Detected by Fermi-LAT Probably Associated with the Thermal Composite Supernova Remnant Kesteven 41 in a Molecular Environment
Hadron emission from supernova remnant (SNR)-molecular cloud (MC) association
systems has been widely regarded as a probe of the shock-accelerated cosmic-ray
protons. Here, we report on the detection of a {\gamma}-ray emission source,
with a significance of 24{\sigma} in 0.2-300 GeV, projected to lie to the
northwest of the thermal composite SNR Kesteven 41, using 5.6 years of
Fermi-Large Area Telescope (LAT) observation data. No significant long-term
variability in the energy range 0.2--300 GeV is detected around this source.
The 3{\sigma} error circle, 0.09 degree; in radius, covers the 1720MHz OH maser
and is essentially consistent with the location of the V_{LSR} ~-50 km/s MC
with which the SNR interacts. The source emission has an exponential cutoff
power-law spectrum with a photon index of 1.9+/-0.1 and a cutoff energy of
4.0+/-0.9 GeV, and the corresponding 0.2-300 GeV luminosity is ~1.3*10^36 erg/s
at a distance of 12 kpc. There is no radio pulsar in the 3{\sigma} circle
responsible for the high {\gamma}-ray luminosity. While the inverse Compton
scattering scenario would lead to a difficulty in the electron energy budget,
the source emission can naturally be explained by the hadronic interaction
between the relativistic protons accelerated by the shock of SNR Kesteven 41
and the adjacent northwestern MC. In this paper, we present a list of Galactic
thermal composite SNRs detected at GeV {\gamma}-ray energies by Fermi-LAT is
presented
Characterization of the dynamic mechanical properties of low-iron float glass through Split-Hopkinson-Pressure-Bar tests
- …