Detection of an Orphan X-Ray Flare from a Blazar Candidate EP240709a with the Einstein Probe
Abstract Blazars are often observed to flare across multiple wavelengths. Orphan flares from blazars have only been detected a few times, providing an opportunity to understand the structure of the jet in the accreting system. We report a remarkable orphan X-ray flare from a blazar candidate EP240709a, detected by the Einstein Probe (EP) in July 2024. The multiband spectral properties and variability support EP240709a as a high-energy peaked BL Lacertae-type object. The flux in 0.5–10 keV increased by at least 28 times to the value of low state in 2020, with no significant flaring detected in other bands during the same period. EP240709a exhibits the harder-when-brighter tendency in the X-ray band during the orphan flare, while its infrared-optical spectra are featureless. We employ one-zone and two-zone leptonic synchrotron self-Compton models to perform the spectral energy distribution fitting. Detecting this rare orphan flare shows the potential of EP in discovering peculiar activities from AGN in high-cadence X-ray sky surveys.
Authors
- An Li (ORCID: https://orcid.org/0000-0002-0823-4317)
- Weimin Yuan (ORCID: https://orcid.org/0000-0001-8266-3024)
- Rui Xue (ORCID: https://orcid.org/0000-0003-1721-151X)
- Moira Andrews (ORCID: https://orcid.org/0000-0002-1895-6639)
- S. M. Jia (ORCID: https://orcid.org/0000-0002-5203-8321)
- Hubing Xiao (ORCID: https://orcid.org/0000-0001-8244-1229)
- Chichuan Jin (ORCID: https://orcid.org/0000-0002-2006-1615)
- Yong Chen (ORCID: https://orcid.org/0000-0001-9834-2196)
- Qinyu Wu (ORCID: https://orcid.org/0009-0002-9275-715X)
- Dongyue Li (ORCID: https://orcid.org/0000-0002-4562-7179)
- Ze-Rui Wang (ORCID: https://orcid.org/0000-0002-3883-6669)
- He‐Yang Liu (ORCID: https://orcid.org/0000-0002-2412-5751)
- Shao-Yu Fu (ORCID: https://orcid.org/0009-0002-7730-3985)
- Tzi-Wei Lian
- Lixin Dai (ORCID: https://orcid.org/0000-0002-9589-5235)
- Samaporn Tinyanont (ORCID: https://orcid.org/0000-0002-1481-4676)
- Haiwu Pan (ORCID: https://orcid.org/0000-0001-5249-2797)
- I. M. Monageng (ORCID: https://orcid.org/0000-0002-4754-3526)
- Chengkui Li
- Estefania Padilla Gonzalez (ORCID: https://orcid.org/0000-0003-0209-9246)
- Rungrit Anutarawiramkul (ORCID: https://orcid.org/0000-0002-4342-2647)
- Huaqing Cheng (ORCID: https://orcid.org/0000-0003-4200-9954)
- D. A. H. Buckley (ORCID: https://orcid.org/0000-0002-7004-9956)
- Ning-Chen Sun (ORCID: https://orcid.org/0000-0002-4731-9698)
- Xinpeng Xu
- Dingrong Xiong (ORCID: https://orcid.org/0000-0002-6809-9575)
- Joseph Farah (ORCID: https://orcid.org/0000-0003-4914-5625)
- Yun Wang (ORCID: https://orcid.org/0000-0002-8385-7848)
- Yijia Zhang (ORCID: https://orcid.org/0000-0001-8541-7072)
- G. Terreran (ORCID: https://orcid.org/0000-0003-0794-5982)
- D. Xu (ORCID: https://orcid.org/0000-0003-3257-9435)
- C. McCully (ORCID: https://orcid.org/0000-0001-5807-7893)
- Haonan Yang (ORCID: https://orcid.org/0000-0002-7680-2056)
- Megan Newsome (ORCID: https://orcid.org/0000-0001-9570-0584)
- D. A. Howell (ORCID: https://orcid.org/0000-0003-4253-656X)
- Suijian Xue (ORCID: https://orcid.org/0000-0002-0660-0432)
- Jie An (ORCID: https://orcid.org/0000-0002-0028-0079)
- Wenxiong Li (ORCID: https://orcid.org/0000-0002-0096-3523)
- Jun Yang (ORCID: https://orcid.org/0000-0002-5485-5042)
- Hua Feng (ORCID: https://orcid.org/0000-0001-7584-6236)
- Xing Liu (ORCID: https://orcid.org/0000-0002-7480-5085)
- Wei Cui (ORCID: https://orcid.org/0000-0002-6324-5772)
- Wenda Zhang (ORCID: https://orcid.org/0000-0001-5647-7762)
- Zhen Guo (ORCID: https://orcid.org/0000-0002-3769-0557)
- Mingjun Liu (ORCID: https://orcid.org/0009-0009-8982-2361)
- Lingzhi Wang (ORCID: https://orcid.org/0000-0002-1094-3817)
- X. -J. Sun
- Cui-Yuan Dai
- Hu Zou (ORCID: https://orcid.org/0000-0002-6684-3997)
- Shuai-Qing Jiang
- Wenjie Zhang (ORCID: https://orcid.org/0009-0003-9214-7316)
- Y. F. Liang (ORCID: https://orcid.org/0009-0005-0170-192X)
- J. Mao (ORCID: https://orcid.org/0009-0009-0593-4543)
- Jin Zhang (ORCID: https://orcid.org/0000-0003-3554-2996)
- Pathompong Butpan
- Yuan Liu (ORCID: https://orcid.org/0000-0001-6676-6875)
Institutions
- Beijing Institute of Technology (CN)
- University of Science and Technology of China (CN)
- Las Cumbres Observatory Global Telescope Network (US)
- Space Telescope Science Institute (US)
- Adler Planetarium (US)
- Zhejiang Normal University (CN)
- University of California, Santa Barbara (US)
- University of Cape Town (ZA)
- Chinese Academy of Sciences (CN)
- Shanghai Normal University (CN)
- Beijing Normal University (CN)
- University of the Free State (ZA)
- Yunnan Observatories (CN)
- Purple Mountain Observatory (CN)
- Max Planck Institute for Extraterrestrial Physics (DE)
- Millennium Institute of Astrophysics (CL)
- Qilu Normal University (CN)
- South African Radio Astronomy Observatory (ZA)
- Université Bourgogne Franche-Comté (FR)
- Institute of High Energy Physics (CN)
- National Astronomical Observatories (CN)
- University of Chinese Academy of Sciences (CN)
- University of Valparaíso (CL)
- National Astronomical Research Institute of Thailand (TH)
- Nanjing University (CN)
- University of Hong Kong (HK)
- Tsinghua University (CN)
Publication Details
- Journal
- The Astrophysical Journal
- Published
- 2025-04-21
- DOI
- https://doi.org/10.3847/1538-4357/adc301
- Citations
- 4
- Primary Topic
- Astrophysics and Cosmic Phenomena
- Type
- article
- Field-Weighted Citation Impact
- 7.48
Funders
- China Postdoctoral Science Foundation
- China Scholarship Council