J/A+A/668/A39 SNR CTB87 14.7GHz and 17.3GHz total intensity maps (Reich+, 2022)
Extended radio halo of the supernova remnant CTB87 (G74.9+1.2).
Reich W., Reich P., Kothes R.
<Astron. Astrophys. 668, A39 (2022)>
=2022A&A...668A..39R 2022A&A...668A..39R (SIMBAD/NED BibCode)
ADC_Keywords: Supernova remnants ; Radio sources
Keywords: supernovae: individual: CTB87 - radiation mechanisms: non-thermal
Abstract:
Breaks in the radio spectra of supernova remnants (SNRs) reflect the
maximum energy of either shock-accelerated electrons or - in the case
of pulsar wind nebulae - of electrons injected by the central pulsar.
Otherwise, the break may result from energy losses due to synchrotron
ageing or it is caused by energy-dependent diffusion. A spectral
steepening of the plerionic SNR CTB87 at around 11 GHz was observed in
the 1980s, but a recent analysis of CTB87's energetic properties based
on new radio data raised doubt on it. CTB87 consists of a central
compact component surrounded by a diffuse, centrally peaked, almost
circular halo. Missing faint halo emission due to insufficient
sensitivity of early high-frequency observations may be the reason for
the reported spectral break. We intend to clarify the high-frequency
spectrum of CTB87 by new sensitive observations. We used the
broad-band 2-cm receiver at the Effelsberg 100-m telescope for
sensitive continuum observations of CTB87 and its halo in two
frequency bands. The new 2-cm maps of CTB87 show halo emission with a
diameter of about 17' or 30pc for a distance 6.1 kpc in agreement
with lower-frequency data. The measured flux densities are
significantly higher than those reported earlier. The new 2-cm data
establish the high-frequency continuation of CTB87's low-frequency
spectrum. Any significant high-frequency spectral bend or break is
constrained to frequencies well above about 18GHz. The extended halo
of CTB87 has a faint counterpart in gamma-rays (VER J2016+37) and thus
indicates a common origin of the emitting electrons.
Description:
We used the broad-band λ2cm (Ku-band) receiver in the secondary
focus of the Effelsberg 100-m telescope during three, almost clear
nights in May 2020 and we observed CTB87 with the aim to accurately
trace its halo emission.
The four cooled HEMT amplifiers cover the frequency interval from
12GHz to 18GHz. This 6-GHz wide band is split into two 2.5-GHz wide
frequency bands centred at 14.25GHz and 16.75GHz, respectively.
Objects:
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RA (2000) DE Designation(s)
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20 16 01.8 +37 12 53 CTB87 = VER J2016+371
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 83 2 List of fits maps
fits/* . 2 Individual fits maps
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1 A1 --- --- [G]
2- 10 F9.5 deg GLON Galactic longitude of center (J2000)
11- 19 F9.5 deg GLAT Galactic latitude of center (J2000)
21- 22 I2 --- Nx Number of pixels along X-axis
24- 25 I2 --- Ny Number of pixels along Y-axis
27- 30 F4.1 GHz Freq Obaerved frequency
32- 33 I2 Kibyte size Size of FITS file
35- 49 A15 --- FileName Name of FITS file, in subdirectory fits
51- 83 A33 --- Title Title of the FITS file
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Acknowledgements:
Wolfgang Reich, wreich(at)mpifr-bonn.mpg.de
(End) Patricia Vannier [CDS] 19-Sep-2022