Using the extended Röntgen Survey Imaging Telescope Array (eROSITA) instrument aboard the Spektr-RG spacecraft, astronomers have detected a new large supernova remnant (SNR) in x-rays. The new object, nicknamed “Hoinga”, turns out to be one of the largest SNRs discovered at wavelengths other than radio. The discovery is reported in an article published on February 26 on the arXiv preprint server.
SNRs are diffuse expanding structures resulting from a supernova explosion. They contain expanding ejected material from the explosion and other interstellar material that was swept away by the passage of the blast wave from the exploded star.
Studies of supernova remnants are important to astronomers because they play a key role in the evolution of galaxies, dispersing heavy elements from the supernova explosion and providing the energy needed to heat the interstellar medium (ISM). . SNRs are also believed to be responsible for accelerating galactic cosmic rays.
Researchers assume that our Milky Way galaxy harbors around 1,200 SNRs; however, only 300 of them have been identified to date, mainly through radio surveys. Some projects, like the eROSITA All-Sky Survey (eRASS), can be used to detect new SNRs in x-rays, and recently a team of astronomers led by Werner Becker of the Max Planck Institute for Alien Physics in Garching, Germany, reported such a discovery.
“Using data from the first sky survey from the SRG / eROSITA observatory, we discovered one of the largest SNRs in the sky,” the astronomers wrote in the journal.
The new SNR, designated G249.5 + 24.5, was called Hoinga – this is the medieval name of Becker’s hometown, Bad Hönningen am Rhein. Observations show that Hoinga has a diameter of about 4◦.4, “therefore, it is almost the largest SNR ever detected at radio wavelengths and comparable in size to the largest detected object of this type, G65.3 + 5.7.
Hoinga exhibits a circular shaped morphology with diffuse X-ray emission filling in almost everything else. It has a clear hull structure, which suggests that it is a classic hull type SNR, not centrally fed. The researchers noted that its highly circular nature indicates that it extends in a region of relatively uniform density.
Based on the data, astronomers estimated that Hoinga had a gas temperature of around 0.1 keV and an absorbent column density of around 360 quintillion cm.−2. The radio-spectral index was found to be at a level of -0.69, and the distance to the remainder was calculated to be most likely 1,600 light years. The age of this SNR is assumed to be between 21,000 and 150,000 years.
“From its size and its X-ray and radio spectral properties, we conclude that Hoinga is a middle-aged Vela-type SNR located at a distance of approximately twice that of the Vela SNR, ie at ∼500 pc” , the paper authors concluded.
Hoinga: Starburst debris found in an unexpected location
Hoinga: Supernova remnant discovered in SRG / eROSITA All-Sky Survey eRASS1, arXiv: 2102.13449 [astro-ph.HE] arxiv.org/abs/2102.13449
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