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EP250207b is not a collapsar fast X-ray transient. Is it due to a compact object merger?

Fast X-ray Transients (FXTs) are short-lived extra-galactic X-ray sources. Recent progress through multi-wavelength follow-up of Einstein Probe discovered FXTs has shown that several are related to collapsars, which can also produce…

High Energy Astrophysical Phenomena · Physics 2025-12-17 P. G. Jonker , A. J. Levan , Xing Liu , Dong Xu , Yuan Liu , Xinpeng Xu , An Li , N. Sarin , N. R. Tanvir , G. P. Lamb , M. E. Ravasio , J. Sánchez-Sierras , J. A. Quirola-Vásquez , B. C. Rayson , J. N. D. van Dalen , D. B. Malesani , A. P. C. van Hoof , F. E. Bauer , J. Chacón , S. J. Smartt , A. Martin-Carrillo , G. Corcoran , L. Cotter , A. Rossi , F. Onori , M. Fraser , P. T. O'Brien , R. A. J. Eyles-Ferris , J. Hjorth , T. -W. Chen , G. Leloudas , L. Tomasella , S. Schulze , M. De Pasquale , F. Carotenuto , J. Bright , Chenwei Wang , Shaolin Xiong , Jinpeng Zhang , Wangchen Xue , Jiacong Liu , Chengkui Li , D. Mata Sanchez , M. A. P. Torres

EP 250108a/SN 2025kg: Observations of the most nearby Broad-Line Type Ic Supernova following an Einstein Probe Fast X-ray Transient

With a small sample of fast X-ray transients (FXTs) with multi-wavelength counterparts discovered to date, the progenitors of FXTs and their connections to gamma-ray bursts (GRBs) and supernovae (SNe) remain ambiguous. Here, we present…

High Energy Astrophysical Phenomena · Physics 2025-06-19 J. C. Rastinejad , A. J. Levan , P. G. Jonker , C. D. Kilpatrick , C. L. Fryer , N. Sarin , B. P. Gompertz , C. Liu , R. A. J. Eyles-Ferris , W. Fong , E. Burns , J. H. Gillanders , I. Mandel , D. B. Malesani , P. T. O'Brien , N. R. Tanvir , K. Ackley , A. Aryan , F. E. Bauer , S. Bloemen , T. de Boer , C. R. Bom , J. A. Chacon , K. Chambers , T. -W. Chen , A. A. Chrimes , J. N. D. van Dalen , V. D'Elia , M. De Pasquale , M. D. Fulton , P. J. Groot , R. Gupta , D. H. Hartmann , A. P. C. van Hoof , M. E. Huber , L. Izzo , W. Jacobson-Galan , P. Jakobsson , A. Kong , T. Laskar , T. B. Lowe , E. A. Magnier , E. Maiorano , A. Martin-Carrillo , L. Mas-Ribas , D. Mata Sanchez , M. Nicholl , C. J. Nixon , S. R. Oates , G. Paek , J. Palmerio , D. Paris , D. L. A. Pieterse , G. Pugliese , J. A. Quirola Vasquez , J. van Roestel , A. Rossi , A. Rouco Escorial. R. Salvaterra , B. Schneider , S. J. Smartt , K. Smith , I. A. Smith , S. Srivastav , M. A. P. Torres , C. Ventura , P. Vreeswijk , R. Wainscoat , Y. -J. Yang , S. Yang

Characterization of a peculiar Einstein Probe transient EP240408a: an exotic gamma-ray burst or an abnormal jetted tidal disruption event?

We present the results of our multi-wavelength (X-ray to radio) follow-up campaign of the Einstein Probe transient EP240408a. The initial 10 s trigger displayed bright soft X-ray (0.5-4 keV) radiation with peak luminosity $L_\textrm{X}…

High Energy Astrophysical Phenomena · Physics 2025-01-14 B. O'Connor , D. Pasham , I. Andreoni , J. Hare , P. Beniamini , E. Troja , R. Ricci , D. Dobie , J. Chakraborty , M. Ng , N. Klingler , V. Karambelkar , S. Rose , S. Schulze , G. Ryan , S. Dichiara , I. Monageng , D. Buckley , L. Hu , G. Srinivasaragavan , G. Bruni , T. Cabrera , S. B. Cenko , H. van Eerten , J. Freeburn , E. Hammerstein , M. Kasliwal , C. Kouveliotou , K. Kunnumkai , J. K. Leung , A. Lien , A. Palmese , T. Sakamoto

An extremely soft and weak fast X-ray transient associated with a luminous supernova

Long gamma-ray bursts (LGRBs), including their subclasses of low-luminosity GRBs (LL-GRBs) and X-ray flashes (XRFs) characterized by low spectral peak energies, are known to be associated with broad-lined Type Ic supernovae (SNe Ic-BL),…

High Energy Astrophysical Phenomena · Physics 2025-04-25 W. -X. Li , Z. -P. Zhu , X. -Z. Zou , J. -J. Geng , L. -D. Liu , Y. -H. Wang , R. -Z. Li , D. Xu , H. Sun , X. -F. Wang , Y. -W. Yu , B. Zhang , X. -F. Wu , Y. Yang , A. V. Filippenko , X. -W. Liu , W. -M. Yuan , D. Aguado , J. An , T. An , D. A. H. Buckley , A. J. Castro-Tirado , S. -Y. Fu , J. P. U. Fynbo , D. A. Howell , J. -W. Hu , S. -Q. Jiang , A. Kumar , J. -R. Mao , J. R. Maund , X. Liu , B. Mockler , A. Moskvitin , M. Andrews , C. R. Bom , T. G. Brink , K. Chatterjee , Y. Chen , H. -Q. Cheng , J. Cooke , J. L. Dai , G. -W. Du , N. Erasmus , Y. Fang , J. Farah , V. Goranskij , M. Gritsevich , M. Gu , Z. Guo , E. Hsiao , Y. -D. Hu , Y. -L. Hua , W. Jacobson-Galán , S. -M. Jia , C. -C. Jin , M. M. Kasliwal , C. D. Kilpatrick , B. Kumar , W. -H. Lei , C. -K. Li , D. -Y. Li , L. -P. Li , Z. -X. Ling , Q. -C. Liu , Y. Liu , Y. -Q. Liu , A. López-Oramas , O. Maslennikova , C. McCully , I. Monageng , M. Newsone , E. Padilla Gonzalez , H. -W. Pan , H. -W. Peng , G. Pignata , F. Poidevin , S. B. Potter , I. Pérez-Fournon , L. Santana-Silva , A. Santos , C. -Y. Song , F. -F. Song , O. Spiridonova , N. -C. Sun , X. -J. Sun , G. Terreran , L. -Z. Wang , L. -F. Wang , B. -T. Wang , Z. -Y. Wang , G. -L. Wu , D. -F. Xiang , H. -F. Xiao , Y. -F. Xu , S. -J. Xue , S. -Y. Yan , Y. -P. Yang , L. -X. Yu , Y. -H. Zhang , Y. -H. Zhang , C. Zhang , J. -H. Zhang , J. -J. Zhang , W. Zheng , H. Zou

EP241021a: A catastrophic collapse/merger of compact star binary leading to the formation of a remnant millisecond magnetar?

Observations of fast X-ray transients (FXRTs) with the Einstein Probe have successfully led to the discovery of some unusual extragalactic optical transients. EP241021a is a newly discovered FXRT that was featured by a significant bump…

High Energy Astrophysical Phenomena · Physics 2025-08-15 Guang-Lei Wu , Yun-Wei Yu , Liang-Duan Liu , Zi-Gao Dai , Wei-Hua Lei , Xue-Feng Wu , Dong Xu , Bing Zhang , Jin-Ping Zhu , Yuan-Chuan Zou

XMM-Newton-discovered Fast X-ray Transients: Host galaxies and limits on contemporaneous detections of optical counterparts

Extragalactic fast X-ray transients (FXTs) are a class of soft (0.3-10 keV) X-ray transients lasting a few hundred seconds to several hours. Several progenitor mechanisms have been suggested to produce FXTs, including supernova shock…

High Energy Astrophysical Phenomena · Physics 2023-12-19 D. Eappachen , P. G. Jonker , J. Quirola-Vásquez , D. Mata Sánchez , A. Inkenhaag , A. J. Levan , M. Fraser , M. A. P. Torres , F. E. Bauer , A. A. Chrimes , D. Stern , M. J. Graham , S. J. Smartt , K. W. Smith , M. E. Ravasio , A. I. Zabludoff , M. Yue , F. Stoppa , D. B. Malesani , N. C. Stone , S. Wen

Einstein Probe discovery of the short period intermediate polar EP J115415.8-501810

The X-ray transient source EP240309a/EP\,J115415.8$-$501810 was first detected by the Wide-Field X-ray Telescope (WXT) on board Einstein Probe (EP) during the commissioning phase. Subsequent optical observations confirmed it as a…

High Energy Astrophysical Phenomena · Physics 2025-09-03 Y. Xiao , M. Ge , N. Rea , F. Lu , H. Feng , L. Tao , D. de Martino , F. Coti Zelati , A. Marino , E. Kuulkers , W. Yuan , C. Jin , H. Sun , J. Wu , N. Hurley-Walker , S. J. McSweeney , D. A. H. Buckley , B. Zhang , S. Zhang , S. Scaringi , K. Mori , Z. Yu , X. Hou , Y. Xu

The Evryscope Fast Transient Engine: Real-Time Detection for Rapidly Evolving Transients

Astrophysical transients with rapid development on sub-hour timescales are intrinsically rare. Due to their short durations, events like stellar superflares, optical flashes from gamma-ray bursts, and shock breakouts from young supernovae…

Instrumentation and Methods for Astrophysics · Physics 2023-04-26 Hank Corbett , Jonathan Carney , Ramses Gonzalez , Octavi Fors , Nathan Galliher , Amy Glazier , Ward S. Howard , Nicholas M. Law , Robert Quimby , Jeffrey K. Ratzloff , Alan Vasquez Soto

Einstein Probe Discovery of EP J182730.0-095633: A New Black Hole X-ray Binary Candidate in Faint Outburst?

Black hole X-ray binaries (candidates) currently identified in our galaxy are mainly transient sources, with the majority discovered through the detection of their X-ray outbursts. Among these, only four were found during faint outbursts…

High Energy Astrophysical Phenomena · Physics 2025-07-18 Huaqing Cheng , Qingchang Zhao , L. Tao , H. Feng , F. Coti Zelati , H. W. Pan , A. L. Wang , Y. N. Wang , M. Y. Ge , A. Rau , A. Marino , L. Zhang , W. J. Zhang , F. Carotenuto , L. Ji , C. C. Jin , D. Y. Li , B. F. Liu , Y. Liu , E. L. Qiao , N. Rea , R. Soria , S. Wang , Z. Yan , W. Yuan , B. Zhang , G. B. Zhang , S. N. Zhang , W. D. Zhang , A. Beardmore , J. S. Bright , X. L. Chen , Z. Fan , S. Y. Fu , J. P. U. Fynbo , J. W. Hu , J. J. Jin , P. G. Jonker , A. K. H. Kong , E. Kuulkers , C. K. Li , H. L. Li , Z. K. Lin , C. X. Liu , H. -Y. Liu , J. Z. Liu , X. W. Liu , Z. Lu , C. Maitra , H. Y. Mu , C. -Y. Ng , Y. L. Qiu , S. Tinyanont , Y. Wang , S. X. Wen , S. S. Weng , Jianfeng Wu , D. Xu , Y. K. Yan , Z. Yan , Y. -P. Yang , P. Zhang , S. Zhang , Q. Zhao , Z. M. Cai , Y. Chen , Y. F. Chen , C. Z. Cui , W. W. Cui , H. B. Hu , M. H. Huang , S. M. Jia , G. Jin , Z. X. Ling , H. Q. Liu , S. L. Sun , X. J. Sun , Y. F. Xu , C. Zhang , M. Zhang , Y. H. Zhang

The Einstein Probe Mission

The Einstein Probe (EP) is a mission designed to monitor the sky in the soft X-ray band. It will perform systematic surveys and characterisation of high-energy transients and monitoring of variable objects at unprecedented sensitivity and…

High Energy Astrophysical Phenomena · Physics 2023-04-05 Weimin Yuan , Chen Zhang , Yong Chen , Zhixing Ling

Representation Learning for Time-Domain High-Energy Astrophysics: Discovery of Extragalactic Fast X-ray Transient XRT 200515

We present a novel representation learning method for downstream tasks like anomaly detection, unsupervised classification, and similarity searches in high-energy data sets. This enabled the discovery of a new extragalactic fast X-ray…

High Energy Astrophysical Phenomena · Physics 2025-03-05 Steven Dillmann , Juan Rafael Martínez-Galarza , Roberto Soria , Rosanne Di Stefano , Vinay L. Kashyap

Multi-wavelength outburst activity from EP J174942.2-384834: a very faint X-ray transient discovered by Einstein Probe

We report the discovery and multi-wavelength characterization of the Galactic transient EP J174942.2$-$384834, first detected by the Einstein Probe during a faint X-ray outburst in March 2025. Coordinated follow-up observations revealed two…

High Energy Astrophysical Phenomena · Physics 2026-05-08 F. Coti Zelati , A. Marino , Y. L. Wang , M. Veresvarska , N. Rea , S. Guillot , D. A. H. Buckley , N. Rawat , S. E. Motta , Y. Xu , Z. Li , Y. -F. Huang , H. Feng , L. Tao , M. Imbrogno , G. Illiano , M. C. Baglio , H. Q. Cheng , C. C. Jin , H. Sun , W. Yuan , F. Carotenuto , R. P. Fender , A. Coleiro , D. Götz , H. L. Li , P. Maggi , Y. L. Qiu , J. Wang , L. P. Xin

Searching for fast extragalactic X-ray transients in Chandra surveys

Recent works have discovered two fast ($\approx 10$ ks) extragalactic X-ray transients in the Chandra Deep Field-South (CDF-S XT1 and XT2). These findings suggest that a large population of similar extragalactic transients might exist in…

High Energy Astrophysical Phenomena · Physics 2019-06-19 Guang Yang , W. N. Brandt , S. F. Zhu , F. E. Bauer , B. Luo , Y. Q. Xue , X. C. Zheng

A fast X-ray transient from a weak relativistic jet associated with a type Ic-BL supernova

Massive stars end their lives as core-collapse supernovae, amongst which some extremes are broad-lined type Ic supernovae from Wolf-Rayet stars associated with long-duration gamma-ray bursts (LGRBs) having powerful relativistic jets. Their…

High Energy Astrophysical Phenomena · Physics 2025-07-15 H. Sun , W. -X. Li , L. -D. Liu , H. Gao , X. -F. Wang , W. Yuan , B. Zhang , A. V. Filippenko , D. Xu , T. An , S. Ai , T. G. Brink , Y. Liu , Y. -Q. Liu , C. -Y. Wang , Q. -Y. Wu , X. -F. Wu , Y. Yang , B. -B. Zhang , W. -K. Zheng , T. Ahumada , Z. -G. Dai , J. Delaunay , N. Elias-Rosa , S. Benetti , S. -Y. Fu , D. A. Howell , Y. -F. Huang , M. M. Kasliwal , V. Karambelkar , R. Stein , W. -H. Lei , T. -Y. Lian , Z. -K. Peng , D. D. Frederiks , A. V. Ridnaia , D. S. Svinkin , X. -Y. Wang , A. -L. Wang , D. -M. Wei , J. An , M. Andrews , J. -M Bai , C. -Y. Dai , S. A. Ehgamberdiev , Z. Fan , J. Farah , H. -C. Feng , J. P. U. Fynbo , W. -J. Guo , Z. Guo , M. -K. Hu , J. -W. Hu , S. -Q. Jiang , J. -J. Jin , A. Li , J. -D. Li , R. -Z. Li , Y. -F. Liang , Z. -X. Ling , X. Liu , J. -R. Mao , C. McCully , D. Mirzaqulov , M. Newsome , E. Padilla Gonzalez , X. Pan , G. Terreran , S. Tinyanont , B. -T. Wang , L. -Z. Wang , X. -D. Wen , D. -F. Xiang , S. -J. Xue , J. Yang , Z. -P. Zhu , Z. -M. Cai , A. J. Castro-Tirado , F. -S. Chen , H. -L. Chen , T. -X. Chen , W. Chen , Y. -H. Chen , Y. -F. Chen , Y. Chen , H. -Q. Cheng , B. Cordier , C. -Z. Cui , W. -W. Cui , Y. -F. Dai , D. -W. Fan , H. Feng , J. Guan , D. -W. Han , D. -J. Hou , H. -B. Hu , M. -H. Huang , J. Huo , S. -M. Jia , Z. -Q. Jia , B. -W. Jiang , C. -C. Jin , G. Jin , E. Kuulkers , C. -K. Li , D. -Y. Li , J. -F. Li , L. -H. Li , M. -S. Li , W. Li , Z. -D. Li , C. -Z Liu , H. -Y. Liu , H. -Q. Liu , M. -J. Liu , F. -J. Lu , L. -D. Luo , J. Ma , X. Mao , K. Nandra , P. O'Brien , H. -W. Pan , A. Rau , N. Rea , J. Sanders , L. -M. Song , S. -L. Sun , X. -J. Sun , Y. -Y. Tan , Q. -J. Tang , Y. -H. Tao , H. Wang , J. Wang , L. Wang , W. -X. Wang , Y. -L. Wang , Y. -S. Wang , D. -R. Xiong , H. -T. Xu , J. -J. Xu , X. -P. Xu , Y. -F. Xu , Z. Xu , C. -B. Xue , Y. -L. Xue , A. -L. Yan , H. -N. Yang , X. -T. Yang , Y. -J. Yang , C. Zhang , J. Zhang , M. Zhang , S. -N. Zhang , W. -D. Zhang , W. -J. Zhang , Y. -H. Zhang , Z. Zhang , Z. Zhang , Z. -L. Zhang , D. -H. Zhao , H. -S. Zhao , X. -F. Zhao , Z. -J. Zhao , Y. -L. Zhou , Y. -X. Zhu , Z. -C. Zhu , H. Zou

Detection of an Orphan X-ray Flare from a Blazar Candidate EP240709a with Einstein Probe

Blazars are often observed to flare across multiple wavelengths. Orphan flares from blazars have been only detected a few times, providing an opportunity to understand the structure of the jet in the accreting system. We report a remarkable…

High Energy Astrophysical Phenomena · Physics 2024-12-25 Mingjun Liu , Yijia Zhang , Yun Wang , Rui Xue , David Buckley , D. Andrew Howell , Chichuan Jin , Wenxiong Li , Itumeleng Monageng , Haiwu Pan , Ning-Chen Sun , Samaporn Tinyanont , Lingzhi Wang , Weimin Yuan , Jie An , Moira Andrews , Rungrit Anutarawiramkul , Pathompong Butpan , Huaqing Cheng , Cui-Yuan Dai , Lixin Dai , Joseph Farah , Hua Feng , Shaoyu Fu , Zhen Guo , Shuaiqing Jiang , An Li , Dongyue Li , Yifang Liang , Heyang Liu , Xing Liu , Yuan Liu , Jirong Mao , Curtis McCully , Megan Newsome , Estefania Padilla Gonzalez , Xin Pan , Xinxiang Sun , Giacomo Terreran , Ze-Rui Wang , Qinyu Wu , Hubing Xiao , Dingrong Xiong , Dong Xu , Xinpeng Xu , Suijian Xue , Haonan Yang , Jun Yang , Jin Zhang , Wenda Zhang , Wenjie Zhang , Hu Zou

JWST and HST observations of the host galaxy and supernova, SN 2024aihh in EP240801a at z=1.67

We present James Webb Space Telescope (JWST) and Hubble Space Telescope (HST) observations of the counterpart of EP240801a, at z=1.67, the first fast X-ray transient (FXT) identified as an X-ray flash (XRF) by the Einstein Probe (EP) and…

High Energy Astrophysical Phenomena · Physics 2025-12-15 Agnes P. C. van Hoof , Andrew J. Levan , Peter G. Jonker , Morgan Fraser , Luca Izzo , Andrew S. Fruchter , Joyce N. D. van Dalen , Nial R. Tanvir , Jens Hjorth , Antonio Martin-Carrillo , Nikhil Sarin , Laura C. Cotter , Jonathan A. Quirola-Vásquez , Maria E. Ravasio , Javi Sánchez-Sierras , Manuel A. P. Torres , Shuai-Qing Jiang , Dong Xu

Fast-transient Searches in Real Time with ZTFReST: Identification of Three Optically-discovered Gamma-ray Burst Afterglows and New Constraints on the Kilonova Rate

While optical surveys regularly discover slow transients like supernovae on their own, the most common way to discover extragalactic fast transients, fading away in a few nights, is via follow-up observations of gamma-ray burst and…

High Energy Astrophysical Phenomena · Physics 2021-09-29 Igor Andreoni , Michael W. Coughlin , Erik C. Kool , Mansi M. Kasliwal , Harsh Kumar , Varun Bhalerao , Ana Sagués Carracedo , Anna Y. Q. Ho , Peter T. H. Pang , Divita Saraogi , Kritti Sharma , Vedant Shenoy , Eric Burns , Tomás Ahumada , Shreya Anand , Leo P. Singer , Daniel A. Perley , Kishalay De , U. C. Fremling , Eric C. Bellm , Mattia Bulla , Arien Crellin-Quick , Tim Dietrich , Andrew Drake , Dmitry A. Duev , Ariel Goobar , Matthew J. Graham , David L. Kaplan , S. R. Kulkarni , Russ R. Laher , Ashish A. Mahabal , David L. Shupe , Jesper Sollerman , Richard Walters , Yuhan Yao

Extragalactic FXT Candidates Discovered by Chandra (2014-2022)

Extragalactic fast X-ray transients (FXTs) are short flashes of X-ray photons of unknown origin that last a few minutes to hours. We extend the search for extragalactic FXTs from Quirola et al. 2022 (Paper I; based on sources in the Chandra…

High Energy Astrophysical Phenomena · Physics 2023-07-05 J. Quirola-Vásquez , F. E. Bauer , P. G. Jonker , W. N. Brandt , G. Yang , A. J. Levan , Y. Q. Xue , D. Eappachen , E. Camacho , M. E. Ravasio , X. C. Zheng , B. Luo

Astro2020 Science White Paper: Discovery Frontiers of Explosive Transients - An ELT & LSST Perspective

The Large Synoptic Survey Telescope (LSST) will open a discovery frontier for faint and fast transients with its ability to detect variable flux components down to $\sim$24.5 mag in a $\sim$30 second exposure. Spectroscopic follow-up of…

High Energy Astrophysical Phenomena · Physics 2019-04-15 Melissa L. Graham , Danny Milisavljevic , Armin Rest , J. Craig Wheeler , Ryan Chornock , Raffaella Margutti , Jeonghee Rho , Chien-Hsiu Lee , Sung-Chul Yoon , Charles D. Kilpatrick , Gautham Narayan , Nathan Smith , G. Grant Williams , Niharika Sravan , Philip Cowperthwaite , Deanne Coppejans , Giacomo Terreran , Adriano Baldeschi , V. Zach Golkhou , Sumner Starrfield

Extragalactic fast X-ray transient candidates discovered by Chandra (2000-2014)

Extragalactic Fast X-ray Transients (FXRTs) are short flashes of X-ray photons spanning a few seconds to hours, with an uncertain origin. Our ignorance about their physical mechanisms and progenitor systems is due in part to the lack of…

High Energy Astrophysical Phenomena · Physics 2022-08-03 J. Quirola-Vasquez , F. E. Bauer , P. G. Jonker , W. N. Brandt , G. Yang , A. J. Levan , Y. Q. Xue , D. Eappachen , X. C. Zheng , B. Luo