49,712 research outputs found
Discovery of a new supernova remnant G150.3+4.5
Large-scale radio continuum surveys have good potential for discovering new
Galactic supernova remnants (SNRs). Surveys of the Galactic plane are often
limited in the Galactic latitude of |b| ~ 5 degree. SNRs at high latitudes,
such as the Cygnus Loop or CTA~1, cannot be detected by surveys in such limited
latitudes. Using the available Urumqi 6 cm Galactic plane survey data, together
with the maps from the extended ongoing 6 cm medium latitude survey, we wish to
discover new SNRs in a large sky area. We searched for shell-like structures
and calculated radio spectra using the Urumqi 6 cm, Effelsberg 11 cm, and 21 cm
survey data. Radio polarized emission and evidence in other wavelengths are
also examined for the characteristics of SNRs. We discover an enclosed
oval-shaped object G150.3+4.5 in the 6 cm survey map. It is about 2.5 degree
wide and 3 degree high. Parts of the shell structures can be identified well in
the 11 cm, 21 cm, and 73.5 cm observations. The Effelsberg 21 cm total
intensity image resembles most of the structures of G150.3+4.5 seen at 6 cm,
but the loop is not closed in the northwest. High resolution images at 21 cm
and 73.5 cm from the Canadian Galactic Plane Survey confirm the extended
emission from the eastern and western shells of G150.3+4.5. We calculated the
radio continuum spectral indices of the eastern and western shells, which are
and between 6 cm and 21 cm, respectively.
The shell-like structures and their non-thermal nature strongly suggest that
G150.3+4.5 is a shell-type SNR. For other objects in the field of view,
G151.4+3.0 and G151.2+2.6, we confirm that the shell-like structure G151.4+3.0
very likely has a SNR origin, while the circular-shaped G151.2+2.6 is an HII
region with a flat radio spectrum, associated with optical filamentary
structure, H, and infrared emission.Comment: 5 pages, 3 figures, accepted for publication of Astronomy and
Astrophysic
Multiple Staggered Mesh Ewald: Boosting the Accuracy of the Smooth Particle Mesh Ewald Method
The smooth particle mesh Ewald (SPME) method is the standard method for
computing the electrostatic interactions in the molecular simulations. In this
work, the multiple staggered mesh Ewald (MSME) method is proposed to boost the
accuracy of the SPME method. Unlike the SPME that achieves higher accuracy by
refining the mesh, the MSME improves the accuracy by averaging the standard
SPME forces computed on, e.g. , staggered meshes. We prove, from theoretical
perspective, that the MSME is as accurate as the SPME, but uses times
less mesh points in a certain parameter range. In the complementary parameter
range, the MSME is as accurate as the SPME with twice of the interpolation
order. The theoretical conclusions are numerically validated both by a uniform
and uncorrelated charge system, and by a three-point-charge water system that
is widely used as solvent for the bio-macromolecules
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