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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. GRB 250920C: TERI Gamma-ray detection
  2. Fermi trigger No 784034269: Global MASTER-Net observations report
  3. Fermi Gamma-ray Burst Monitor trigger 784109140/251106337 is not a GRB
  4. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  5. GRB 251105A: Fermi GBM Observation
  6. GRB 251105C: Fermi GBM Final Localization Correction
  7. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  8. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  9. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  10. GRB 251105B: AstroSat CZTI detection of a short burst with extended emission
  11. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  12. Fermi GBM Sub-Threshold Detection of GRB 251105B
  13. GRB 251103B: Swift/UVOT Upper Limits
  14. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  15. GRB 251105B: SVOM/GRM observation of a possible short burst with extended emission
  16. Fermi GRB 251105A: Global MASTER-Net observations report
  17. GRB 251105A: Fermi GBM Final Real-time Localization
  18. Fermi Gamma-ray Burst Monitor trigger 783986701/251104920 is not a GRB
  19. GRB 251103B: Fermi GBM observation
  20. GRB 251104A: SVOM detection of a burst
  21. GRB 251028A: Insight-HXMT/HE detection
  22. GRB 251103A: Optical afterglow detection by ZTF’s public survey
  23. EP251102a: FTW optical and NIR observations
  24. GRB 251103A: WFST optical observations
  25. EP251102a: update of EP-FXT follow-up observation
  26. EP251102a: OHP/T193 optical observations
  27. GRB 251103A: OHP/T193 optical observations
  28. GRB 251103A: Xinglong 2.16m optical detection
  29. GRB 251103A: Insight-HXMT detection
  30. GRB 251103A: KAIT optical observations
  31. GRB 251103B: Nanshan/HMT optical upper limit
  32. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  33. GRB 251103A: Swift/BAT-GUANO arcminute localization of a burst
  34. GRB 251103B: MITSuME Akeno optical upper limits
  35. GRB 251103B: Swift-XRT refined Analysis
  36. Fermi GRB 251103A: Global MASTER-Net observations report
  37. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  38. EP251102a: NIR observations with WINTER
  39. GRB 251103A: J-band detection with WINTER
  40. Swift GRB 251103B: Global MASTER-Net observations report
  41. GRB 251103B: GROWTH-India Telescope optical upper limits
  42. GRB 251103A: Kilonova-Catcher optical afterglow detection
  43. GRB 251103B: Enhanced Swift-XRT position
  44. GRB 251103B: Prompt enhanced Swift-XRT position
  45. GRB 251103B: Swift detection of a burst
  46. GRB 251103B: Fermi GBM Final Real-time Localization
  47. GRB 251103A: Swift/UVOT Detection
  48. GRB 251103A: Fermi GBM Observation
  49. GRB 251103A: SVOM/GRM observation
  50. GRB 251103A: Swift-XRT afterglow detection
  51. LIGO/Virgo/KAGRA S251031cq: Updated Sky localization
  52. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  53. EP251102a: Einstein Probe detection of a fast X-ray transient
  54. GRB 251025B: OHP/T193 optical upper limit
  55. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  56. GRB 251103A: LCO optical observation
  57. EP251102.890: COLIBRÍ optical counterpart candidate
  58. GRB 251103A: GOTO optical afterglow detection
  59. GRB 251102A: AstroSat CZTI detection
  60. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  61. GRB 251103A: NOT spectroscopic redshift z = 0.76
  62. GRB 251103A: BOOTES-2/TELMA optical afterglow
  63. GRB 251103A: LCO optical afterglow detection
  64. GRB 251103A: NOT optical afterglow candidate (duplicate submission)
  65. GRB 251103A: Fermi GBM Final Localization
  66. GRB 251103A: NOT optical afterglow candidate
  67. GRB 251103A: SVOM detection of a bright burst
  68. GRB 251102B: Fermi GBM Final Real-time Localization
  69. Fermi GRB 251102A: Global MASTER-Net observations report
  70. GRB 251102A: Fermi GBM Final Real-time Localization
  71. GRB 251031A: Fermi GBM Observation
  72. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  73. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  74. Konus-Wind detection of GRB 251028A
  75. GRB 251031A: BALROG localization (Fermi Trigger 783588065 / GRB 251031306)
  76. GRB 251031A: Fermi GBM Final Real-time Localization
  77. GRB 251025C: SVOM/GRM observation
  78. GRB 251028A: GECAM-B detection
  79. GRB 251028A: SVOM/GRM observation
  80. IceCube-251025A: Two Transient Candidates from the Zwicky Transient Facility
  81. GRB 251028A: Fermi GBM Observation
  82. GRB 251026B: SOAR Classification of GOTO25jgl/SN2025absf as a Type Ia supernova
  83. GRB 251022A: Swift-XRT confirmation of fading
  84. GRB 251026B: LBT near-infrared observations
  85. GRB 250926B: VZLUSAT-2 detection
  86. GRB 250926A: VZLUSAT-2 detection
  87. GRB 250925A: VZLUSAT-2 detection
  88. GRB 251026B: Fermi GBM Observation
  89. GRB 251026A/EP251026a: SVOM/VT optical counterpart
  90. GRB 251026A/EP251026a: EP-FXT follow-up observation
  91. The EP-WXT trigger 01709247588 is likely a flaring star
  92. GRB 251028B: Fermi/GBM observation
  93. GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
  94. GRB 251028B: Glowbug gamma-ray detection
  95. GRB 251028A: Glowbug gamma-ray detection
  96. GRB 251028B: CALET Gamma-Ray Burst Monitor detection
  97. Fermi GRB 251028B: Global MASTER-Net observations report
  98. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
  99. GRB 251028B: Fermi GBM Final Localization Correction
  100. GRB251026B: PRIME H-band upper limit

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