![\"Astronomers](\"https:\/\/www.newsbeep.com\/us\/wp-content\/uploads\/2025\/11\/astronomers-discover-n-1.jpg\" "\\"Combined")
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Combined XMM-Newton EPIC image of NGC 4631 in the 0.3\u201310 keV band from the July 2025 observation. The locations of known ULXs and the new ULX X\u22128 are marked. Credit: arXiv (2025). DOI: 10.48550\/arxiv.2511.04282<\/p>\n
Using ESA’s XMM-Newton satellite, European astronomers have observed ultraluminous X-ray sources (ULXs) in the galaxy NGC 4631. As a result, they detected a new pulsating ULX, which received the designation X-8. The research is published<\/a> November 6 on the arXiv preprint server.<\/p>\n \t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tThe nature of ULXs still baffles scientists<\/p>\n ULXs are point sources in the sky that are so bright in X-rays that each emits more radiation than a million suns emit at all wavelengths. They are less luminous than active galactic nuclei<\/a>, but more consistently luminous than any known stellar process. Although numerous studies of ULXs have been conducted, the basic nature of these sources still remains unknown.<\/p>\n Some persistent ULXs exhibit pulsations and therefore are categorized as ultraluminous X-ray pulsars (ULXPs). Discovering and studying objects of this type could be crucial for advancing our understanding of accretion physics\u2014for instance, mechanisms that enable the sustained X-ray luminosities of ULXs which exceed the Eddington limit.<\/p>\n One of many in the Whale galaxy<\/p>\n NGC 4631, dubbed the Whale galaxy, is a late-type starburst galaxy at a distance of some 24.45 million light years<\/a>, known to host at least seven ULXs. A team of astronomers led by Lorenzo Ducci of the University of T\u00fcbingen in Germany, decided to investigate this galaxy in detail with the use of XMM-Newton’s European Photon Imaging Camera (EPIC). Focusing on the ULXs in NGC 4631, they discovered what appears to be a new pulsating ultraluminous X-ray source.<\/p>\n “In this letter, we report the discovery of pulsations from a new ULX located in a crowded region of the galactic disk of NGC 4631,” the researchers wrote.<\/p>\n The observations, carried out in July 2025, identified a significant signal for the period of approximately 9.66 seconds from a new source very close to the previously known ULX designated X\u22122. The new source received the designation X-8 and turned out to be brighter than X\u22122, with an X-ray luminosity at a level of 3.4 duodecillion erg\/s.<\/p>\n \t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tSpeeding up and pulsating<\/p>\n The observations found that X-8 has a spin period derivative of about \u22129.6 \u00d7 10\u22128 seconds\/second. Therefore, X\u22128 shows one of the most rapid spin-up rates observed in pulsating ULXs, with a spin-up timescale (spin period\/spin period derivative) of only 3.2 years.<\/p>\n The astronomers noted that such a high spin-up rate of X-8 could originate from orbital motion of the pulsar, accretion torque on the neutron star, or a combination of both mechanisms.<\/p>\n The study also found that the magnetic field strength of the newfound ULXP should be within a range of 10\u2013200 trillion Gauss, which is consistent with the magnetic field strengths inferred by other pulsating ultraluminous X-ray sources.<\/p>\n Summing up the results, the authors of the paper underscored the importance of their discovery in the context of super-Eddington luminosities studies.<\/p>\n “This new ULX pulsar adds a key source to the small known population, and will enable future studies to better constrain the physical mechanisms responsible for their super-Eddington luminosities,” the scientists concluded.<\/p>\n \n Written for you by our author Tomasz Nowakowski<\/a>, edited by Gaby Clark<\/a>, and fact-checked and reviewed by Robert Egan<\/a>\u2014this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. More information: \n\t\t\t\t\t\t\t\t\t\t\t\t\tJournal information: \t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/p>\n \n\t\t\t\t\t\t\t\t\t\t\t\t \u00a9 2025 Science X Network\n\t\t\t\t\t\t\t\t\t\t\t <\/p>\n \n\t\t\t\t\t\t\t\t\t\t\t\tCitation: \n\t\t\t\t\t\t\t\t\t\t\t This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
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\n\t\t\t\t\t\t\t\t\t\t\t\tL. Ducci et al, Discovery of a 9.67-s pulsar in an ultraluminous X-ray source in NGC 4631 with XMM-Newton, arXiv (2025). DOI: 10.48550\/arxiv.2511.04282<\/a><\/p>\n
\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tarXiv<\/a>
\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/p>\n
\n\t\t\t\t\t\t\t\t\t\t\t\tAstronomers discover new pulsating ultraluminous X-ray source (2025, November 12)
\n\t\t\t\t\t\t\t\t\t\t\t\tretrieved 12 November 2025
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