28 research outputs found
Is the Cygnus Loop two supernova remnants?
The Cygnus Loop is classified as a middle-aged supernova remnant (SNR)
located below the Galactic equator (l=74, b=-8.6) and 770 pc away from us. Its
large size and little confusion with Galactic emission makes it an ideal test
ground for evolutionary and structural theories of SNRs. New radio continuum
mapping of the Cygnus Loop at 2695 MHz with the Effelsberg 100-m telescope
provides indications that the Cygnus Loop consists of two separate SNRs.
Combining this result with data from the literature we argue that a secondary
SNR exists in the south with a recently detected neutron star close to its
center. Two interacting SNRs seem to be the best explanation to account for the
Cygnus Loop observations at all wavelengths.Comment: 4 pages, 2 figures, Astron. Astrophys., accepte
Radio emission from the Cygnus Loop and its spectral characteristics
We present a new sensitive 2675 MHz radio continuum map of the Cygnus Loop,
which is used in conjunction with 408 MHz, 863 MHz and 1420 MHz maps from both
the Effelsberg 100-m telescope and the DRAO Synthesis Telescope for a spectral
analysis. Between 408 MHz and 2675 MHz we find an overall integrated spectral
index of (), close to
previous results. There is no indication of a spectral break in the integrated
spectrum. Spatially highly varying and rather strong spectral curvature was
previously reported, but is not confirmed on the basis of new, higher
sensitivity observations. We found spectral variations across the Cygnus Loop
reaching up to from a TT-plot analysis. The flattest
spectra are seen towards enhanced emission areas. Spectral index maps produced
between different frequency pairs, as well as all four maps, revealed that
there are at least three flat spectrum regions. In regions interior to the high
emission filaments, we have detected at least two spectral components across
the whole object with and towards northern and
southern parts of the object, respectively.Comment: 22 pages, 13 figures in jpeg format, accepted for publication in
Astrophysics & Astronom
The Cygnus superbubble revisited
The Orion local spiral arm is seen tangential
towards the Cygnus region. Intense radio emission with quite a
complex morphology is observed, which appears to be
surrounded by strong soft X-ray emission. This remarkable
X-ray structure is known as the Cygnus superbubble. We
compare a recent 1.4 GHz radio continuum and polarization
map from the Effelsberg 100-m telescope with X-ray data from
the ROSAT all-sky survey of this area. Including available survey
data of the infrared, H
A catalogue of Galactic supernova remnants from the Canadian Galactic plane survey
We present a new catalogue containing all known Galactic supernova
remnants observed in phase I and II of the Canadian Galactic Plane Survey
(65\degr \leq \ell \leq 175\degr, -5\degr \leq b \leq +7\degr).
Stokes I images at 1420Â MHz of 34 SNRs and at 408Â MHz of 36Â SNRs
are displayed. From these 1\arcmin and
3\arcmin-resolution data (respectively) we determine accurate centre
positions and angular dimensions. The flux densities at 1420 and 408 MHz are
integrated and combined with values from the literature to define more
accurate radio spectra. The CGPS polarization data at 1420Â MHz were examined
and significant linear polarization from 18 SNRs is found, with a modest
signal from 6 others.
A 1.4Â GHz radio continuum and polarization survey at medium Galactic latitudes
We present the first section of a radio continuum and
polarization survey at medium Galactic latitudes carried out with the
Effelsberg 100-m telescope at 1.4Â GHz. Four large fields have been
observed, which all together cover an area of about .
The rms-sensitivity is about 15Â mKÂ TB (about 7Â mJy/beam
area) in total intensity and is limited by confusion. A sensitivity of
8Â mKÂ TB is obtained in linear polarization. The angular
resolution of the observations is 9
l35. The maps in total
intensity and linear polarization have been absolutely calibrated by
low resolution data where ava ilable. Significant linear polarization is
seen in all the maps. In general, the intensity fluctuations measured
in linear polarization are not correlated with total intensity
structures. Areas of high polarization of some degrees extent are
seen, again with no apparent corresponding total intensity feature.
Modulation of polarized background emission by spatially varying
Faraday rotation seems the most likely explanation. Quite unexpected
is the detection of filamentary and ring-like depolarization
structures in the direction of the anticentre region, whose extents are up to
about