Using the MAGIC telescope and NASA's Fermi spacecraft, a team of international astronomers have discovered a new source of very high energy gamma ray emissions around the remaining supernova (SNR) G24.7 + 0.6. Detecting new sources, designated MAGIC J1835-069, is detailed in a paper published December 12 on the arXiv pre-printed server.
Supernova remnants are basically the remains of a large star that ended their lives in a large explosion called a supernova. Astronomers generally distinguish three types of SNR, one of which is composite SNR – this has a shell that extends rapidly from supernova explosion waves accompanied by nebular winds powered by young pulsars formed in explosions.
Observations show that composite SNRs are known to accelerate particles to very high energy (VHE), up to hundreds of TeVs or more, in widespread shocks or relativistic winds that surround energetic pulsars. Therefore, the object is a very good target for observation that focuses on finding new sources of VHE emissions.
Located around 16,300 light years, SNR G24.7 + 0.6 is an example of middle-aged (about 9,500 years) radio SNR and gamma ray composites. A group of astronomers have carried out studies on these remains using the MAGIC (Major Atmospheric Gamma Imaging Cherenkov Telescopes) system at the Roque de los Muchachos Observatory in the Canary Islands and the Large Area Telescope (LAT) on NASA's Telescope Fermi Gamma-ray Space.
The data provided by this telescope allows the team to identify VHE emissions from extended sources located 0.34 degrees from the center G24.7 + 0.6, which receives the designation MAGIC J1835-069.
"In this paper, we study an interesting region centered around SNR G24.7 + 0.6 with Fermi-LAT in an energy range between 60 MeV and 500 GeV. We also explore the MAGIC telescope in the surrounding area to investigate the spectral behavior above 150 GeV to limit the area of emissions observed by Fermi-LAT around SNR, "the researchers wrote in the paper.
Emissions from MAGIC J1835-069 are found in energy above 150 GeV and have been detected up to 5 TeV. This source spectrum is well represented by the legal function of power with a spectral index of 2.74.
Emissions from MAGIC J1835-069 also have a projected size of about 98 light years and display expanded morphology. The newly discovered source is located between two broad sources known to be detected above 10 GeV by Fermi-LAT, namely FGES J1836.5-0652 and FGES J1834.1-07070.
The origin of VHE gamma ray emission from MAGIC J1835-069 remains uncertain due to the complexity of the neighboring region G24.7 + 0.6. However, the authors of this paper suggest that it can be explained by accelerated cosmic rays in the remainder of the interaction through the collision of protons with the surrounding media rich in carbon monoxide.
"Detected gamma ray emissions can be interpreted as the result of proton-proton interactions between supernovae and CO-rich environments," the researchers concluded.
The ghost fades from a long-dead star
MAGIC Collaboration. The discovery of TeV-ray emissions from the supernova environment remaining G24.7 + 0.6 by MAGIC. arXiv: 1812.04854 [astro-ph.HE]. arxiv.org/abs/1812.04854