ING scientific news |
9 December, 2022
Possible Discovery of a Supernova Remnant Around the Calvera Pulsar
While analysing data from the LOFAR Two-Metre Sky Survey
(LoTSS, a radio survey at 150 MHz), a team of astronomers discovered a ring of
diffuse emission around the Calvera pulsar. The ring is large, at
approximately one degree, and sits in a region otherwise empty of
large-scale radio emission.
Typically, large sources like these are of Galactic origin, and they can
be of two kinds: H II regions (the ionised bubbles around massive stars),
or supernova remnants (the leftover stellar ejecta and swept-up ambient
medium that results from a supernova explosion). These sources have
different emission mechanisms, and so multi-wavelength
information is required to differentiate them. Observing the optical emission is a primary means to do so.
Luckily, the students in the Leiden astronomy Master's program
visited the Isaac Newton Telescope (INT) as part of their practical observing course in March 2022. They performed follow-up H-alpha observations of the ring only two months after its discovery. The lack of visible optical emission
coinciding with the ring supports the supernova remnant interpretation,
since H II regions emit profusely in H-alpha. The students did find a
small smudge of optical emission, indicative that the supernova remnant
shock might have encountered a density discontinuity and slowed down in
that location (see accompanying figures).
Left: LOFAR 150-MHz image, showing a diffuse radio ring, bounded by the large dotted circles. A cross marks the estimated centre of the ring. The location of the Calvera pulsar is indicated with a small circle, and its
trajectory from 10,000 years in the
past to 10,000 years into the future, according to proper-motion measurements, with a black arrow. The dashed lines indicate the propagated 1-sigma positional uncertainty due to proper motion. The dashed circle denotes the location of diffuse X-ray emission, with the square indicating the location of H-alpha emission.
Right: The H-alpha smudge seen with the INT (see also next figure) and in red the location of diffuse X-ray emission.
Large format: PNG
Detection of extended H-alpha emission in the INT/WFC observations. (a) Image through the H-alpha filter. (b) Image through the r filter . (c) Continuum-subtracted image, i.e. (a) minus (b). Each panel shows a 4 arcmin × 4 arcmin field of view, with the dashed circle representing the extent of the diffuse X-ray emission. Radio contours from LOFAR are overlaid in panel a. Large format: PNG
All the visiting students from Leiden were co-authors in the study, along with the LOFAR team, and one of
the students submitted a follow-up INT proposal to perform spectroscopy on the
optical smudge in order to determine its composition. This research is
an excellent showcase for the use of INT time for teaching.
About the Isaac Newton Telescope
Based on observations made with the Isaac Newton Telescope (INT) operated on the island of La Palma by the Isaac Newton Group of Telescopes (ING) in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias (IAC). The ING is funded by the Science and Technology Facilities Council (STFC-UKRI) of the United Kingdom, the Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) of the Netherlands, and the IAC in Spain. IAC's contribution to ING is funded by the Spanish Ministry of Science, Innovation and Universities.
Arias, M. ; Botteon, A. search by orcid ; Bassa, C. G. ; van der Jagt, S. ; van Weeren, R. J. ; O'Sullivan, S. P. ; Bosschaart, Q. ; Dullaart, R. S. ; Hardcastle, M. J. ; Hessels, J. W. T. ; Shimwell, T. ; Slob, M. M. ; Sturm, J. A. ; Tasse, C. ; Theijssen, N. C. M. A. ; Vink, J., 2022, "Possible discovery of Calvera's supernova remnant", A&A, 667, A71 [ Paper ].
"Leiden University Observing Trips to the INT", ING web news, 12th July 2022.