| Issue |
A&A
Volume 668, December 2022
|
|
|---|---|---|
| Article Number | A39 | |
| Number of page(s) | 6 | |
| Section | Interstellar and circumstellar matter | |
| DOI | https://doi.org/10.1051/0004-6361/202244741 | |
| Published online | 01 December 2022 | |
Extended radio halo of the supernova remnant CTB87 (G74.9+1.2)★
1
Max-Planck-Institut für Radioastronomie,
Auf dem Hügel 69,
53121
Bonn, Germany
e-mail: wreich@mpifr-bonn.mpg.de; preich@mpifr-bonn.mpg.de
2
National Research Council of Canada, Dominion Radio Astrophysical Observatory,
PO Box 248,
Penticton BC
V2A 6J9, Canada
e-mail: Roland.Kothes@nrc-cnrc.gc.ca
Received:
11
August
2022
Accepted:
1
September
2022
Context. 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.
Aims. We intend to clarify the high-frequency spectrum of CTB87 by new sensitive observations.
Methods. We used the broad-band λ2 cm receiver at the Effelsberg 100-m telescope for sensitive continuum observations of CTB87 and its halo in two frequency bands.
Results. The new λ2 cm maps of CTB87 show halo emission with a diameter of about 17′ or 30 pc for a distance of 6.1 kpc in agreement with lower-frequency data. The measured flux densities are significantly higher than those reported earlier.
Conclusions. The new λ2 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 18 GHz. The extended halo of CTB87 has a faint counterpart in γ rays (VER J2016+37) and thus indicates a common origin of the emitting electrons.
Key words: supernovae: individual: CTB87 / radiation mechanisms: non-thermal
CTB87 maps at 14.7 GHz and 17.3 GHz are also available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/668/A39
© W. Reich et al. 2022
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
This article is published in open access under the Subscribe-to-Open model.
Open Access funding provided by Max Planck Society.
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.