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Lead researchers Antonio Martin-Carrillo of University College Dublin<\/a> (UCD) and Andrew J. Levan of Radboud University<\/a> (RU) directed the effort. <\/p>\n Their teams combined rapid-response alerts from NASA\u2019s Fermi satellite<\/a>, China\u2019s Einstein Probe, and follow-up observations with the Very Large Telescope (VLT<\/a>) and the Hubble Space Telescope<\/a>.<\/p>\n Martin-Carrillo called it \u201cunlike any other seen in 50 years of GRB observations. This is 100 to 1,000 times longer than most GRBs. More importantly, gamma-ray bursts never repeat since the event that produces them is catastrophic.\u201d\u00a0<\/p>\n What makes GRB 250702B so strange<\/p>\n GRBs<\/a> don\u2019t typically don\u2019t happen twice, much less three or more times. Here, Fermi saw three distinct outbursts separated by thousands of seconds, while the Einstein Probe caught earlier X-ray<\/a> activity that started many hours before.<\/p>\n The timing was not random. The third outburst arrived at roughly an integer multiple of the gap between the first two. This pattern suggests at a repeating process inside the source rather than a single one-off blast.<\/p>\n The overall energy in gamma rays is in the same ballpark as other GRBs at similar distances, yet the pattern of activity is different. <\/p>\n Standard relations that link a burst\u2019s peak energy<\/a> to its total output do not align cleanly for each of the three pulses.<\/p>\n The fading afterglow across X-ray, infrared, and radio bands looks normal for a jet from a compact central engine. The near-infrared signal was unusual in one respect: it was extremely red, which suggests heavy dust near the site.<\/p>\n Locating a cosmic mystery<\/p>\n \u201cBefore these observations, the general feeling in the community was that this gamma-ray burst must have originated from within our galaxy,\u201d said Levan. \u201cThe VLT fundamentally changed that paradigm.\u201d <\/p>\n VLT\u2019s HAWK-I camera picked up an extremely red point of light that faded over days.<\/p>\n Hubble<\/a> went a step further and resolved a galaxy at the same spot. That finding places the source in an extragalactic system, likely several billion light-years away. The engine must be extremely powerful to be visible at all.<\/p>\n VLT\u2019s X-shooter spectrograph covered visible to infrared wavelengths and saw a very faint, red continuum, consistent with heavy dust. <\/p>\n While the exact redshift is still being refined, the data point to a relatively nearby cosmic distance compared with many GRBs, which helps explain the sharp view of the host galaxy.<\/p>\n Potential black hole link<\/p>\n One explanation for GRB 250702B points to a jetted tidal disruption event, in which a black hole tears apart a passing star and feeds on the debris. <\/p>\n Astronomers have observed such jets firing erratically in events like Swift J1644+57, described in a paper that modeled how a powerful magnetic field around the black hole could drive on-off behavior.<\/p>\n Another possibility fits the unusual timing. The authors consider a compact white dwarf star<\/a> passing close to an intermediate-mass black hole<\/a>. <\/p>\n This class of black holes is heavier than stellar-mass ones but lighter than the giants in galaxy centers, with masses around 100 to 100,000 times that of the Sun.<\/p>\n In this scenario, the star could be partially stripped during each close pass, feeding the jet in bursts spaced according to the star\u2019s orbit.<\/p>\n Doesn\u2019t fit the mold<\/p>\n A more familiar GRB engine, a collapsing massive star, is not off the table. <\/p>\n The problem is explaining how such a collapse would produce multiple widely spaced pulses over many hours rather than one sustained episode lasting seconds to minutes.<\/p>\n Lensing by a foreground galaxy can also repeat a transient by splitting light paths, but the pulse shapes here differ from one another. The color and afterglow behavior also point away from that lensing explanation.<\/p>\n The first detections were in soft X-rays, then came the brightest gamma-ray flash hours later. That order flips the usual script for GRBs, where the strongest gamma rays typically arrive first and fade quickly.<\/p>\n Infrared light faded quickly, and radio telescopes<\/a> detected a faint source consistent with a standard jet interacting with surrounding gas. <\/p>\n Those observations match the afterglow physics well, even if the prompt high-energy behavior does not fit neatly into existing categories.<\/p>\n The host galaxy is not a nuclear site, which weakens ideas that require a supermassive black hole sitting at the center. If the burst is a disruption event, an off-center intermediate-mass black hole is a better match for the position.<\/p>\n The red color likely comes from dust lanes in the host galaxy that absorb blue light. That dust also lines up with the strong X-ray absorption measured from the same line of sight.<\/p>\n Watching for a supernova<\/p>\n In jet-driven tidal disruption events, X-ray light can plummet once the jet shuts off, while radio emission can rise for months as the blast wave expands. <\/p>\n Continued X-ray and radio monitoring will test whether this source follows that playbook.<\/p>\n If a supernova<\/a> is involved, it would glow in the infrared a few weeks after the collapse. Dust makes that search harder, but large, sensitive telescopes can still look for the telltale rise and fall.<\/p>\n Spectroscopy can also help determine the distance and characterize the environment around the source. <\/p>\n A firm redshift would establish the energy budget and sharpen the comparison to known gamma-ray bursts and disruption events.<\/p>\n \u201cWe are still not sure what produced this, but with this research we have made a huge step forward towards understanding this extremely unusual and exciting object,\u201d said Martin-Carrillo.<\/p>\n The study is published in The Astrophysical Journal Letters<\/a>.<\/p>\n \u2014\u2013<\/p>\n Like what you read? Subscribe to our newsletter<\/a> for engaging articles, exclusive content, and the latest updates.\u00a0<\/p>\n Check us out on EarthSnap<\/a>, a free app brought to you by Eric Ralls<\/a> and Earth.com.<\/p>\n \u2014\u2013<\/p>\n","protected":false},"excerpt":{"rendered":"Earlier this year, astronomers watched a burst of high-energy light that kept roaring back for nearly a full…\n","protected":false},"author":2,"featured_media":20519,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23],"tags":[111,139,69,147,392],"class_list":["post-20518","post","type-post","status-publish","format-standard","has-post-thumbnail","category-space","tag-new-zealand","tag-newzealand","tag-nz","tag-science","tag-space"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/20518","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/comments?post=20518"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/20518\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media\/20519"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media?parent=20518"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/categories?post=20518"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/tags?post=20518"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"This](\"https:\/\/www.newsbeep.com\/nz\/wp-content\/uploads\/2025\/09\/gamma-ray-burst_GRB-250702B_long_repeating_image-sequence_ESO_1s.webp.webp\")
<\/a>This sequence of images shows the evolution over several days of the gamma-ray burst GRB 250702B. The first five images shown here were taken with the VLT\u2019s HAWK-I infrared camera. The explosion, marked here with circles, appears to be nested within an elongated galaxy. An image taken with the NASA\/ESA Hubble Space Telescope (HST) on 15 July, bottom right, confirmed this. The galaxy appears to be seen edge-on, with a dark dust-lane crossing it. Click image to enlarge. Credit: ESO\/A. Levan, A. Martin-Carrillo et al.\/NASA\/ESA Light patterns from GRB 250702B<\/p>\n