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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 251214A: AstroSat CZTI detection
  2. GRB 251213A: GECAM-B detection
  3. GRB 251214B: Swift/UVOT Detection
  4. GRB 251215A: Fermi GBM Final Real-time Localization
  5. GRB 251214B: COLIBRÍ observations of the afterglow
  6. EP251214a: EP-FXT non-detection and upper limit
  7. GRB 251214A: GECAM-B observation of a likely long burst
  8. GRB 251214B: 1.3m DFOT optical detection
  9. EP251214a: Global MASTER-Net observations report
  10. GRB 251214B: Enhanced Swift-XRT position
  11. GRB 251214B: Xinglong-2.16m optical observation
  12. GRB 251214C: Fermi GBM Final Localization
  13. GRB 251214B : MASTER optical afterglow detection
  14. Fermi trigger No 787396657: Global MASTER-Net observations report
  15. GRB 251214B: SVOM/C-GFT optical observations
  16. EP251214a: COLIBRÍ optical upper limit
  17. Swift GRB 251214B: Global MASTER-Net observations report
  18. EP251214.305: COLIBRÍ optical upper limit
  19. GRB 251214B: Swift detection of a burst with an optical counterpart
  20. GRB 251214B: Fermi GBM Final Real-time Localization
  21. EP251214a: EP-WXT detection of an X-ray transient possibly associated with GRB 251214A
  22. Fermi GRB 251214A: Global MASTER-Net observations report
  23. GRB 251214A: Fermi GBM Final Real-time Localization
  24. EP251212a: Global MASTER-Net observations report
  25. EP251212a: KAIT optical upper limit
  26. EP251212a / GRB 251212A: AstroSat CZTI detection
  27. EP251212a: EP-FXT follow-up observation
  28. GRB 251211B: AstroSat CZTI detection
  29. IceCube-251210A: No Candidate Transients from the Zwicky Transient Facility
  30. GRB 251209A: NuSTAR detection of prompt emission
  31. EP251212a : COLIBRÍ optical upper limit
  32. EP251212a: Einstein Probe detection of an X-ray transient
  33. Fermi-LAT Gamma-ray Observations of IceCube-251210A
  34. IceCube-251210A: Upper limits from a search for additional neutrino events in IceCube
  35. Fermi GRB 251211B: Global MASTER-Net observations report
  36. GRB 251211B: Fermi GBM Final Real-time Localization
  37. IceCube-251210A: DDOTI Optical Upper Limit
  38. SVOM GRB251211.12: Global MASTER-Net observations report
  39. GRB 251211A: Fermi GBM Final Real-time Localization
  40. GRB 251209A: Fermi GBM observation
  41. GRB 251205A: 1.3m DFOT optical upper limit
  42. GRB 251209A: AstroSat CZTI detection
  43. IceCube Alert 251210.46: Global MASTER-Net observations report
  44. IceCube-251210A - IceCube observation of a high-energy neutrino candidate track-like event
  45. EP251124a: Mondy optical upper limit
  46. GRB 251129A/EP251129a: AbAO and Mondy optical observations
  47. EP251130a: Mondy and AbAO optical observations
  48. GRB 251208A: AstroSat CZTI detection
  49. Fermi GBM Sub-Threshold Detection of GRB 251205A
  50. GRB 251208A: Glowbug gamma-ray detection
  51. GRB 251208B: COLIBRÍ optical upper limits
  52. EP251118a / GRB 251118C: VLT/MUSE redshift confirmation
  53. GRB 251208C: GECAM-B observation of a short burst
  54. GRB 251208A: GECAM-B observation of a short burst
  55. Fermi GRB 251209A: Global MASTER-Net observations report
  56. Fermi GRB 251208C: Global MASTER-Net observations report
  57. GRB 251206A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  58. GRB 251208B: Swift-XRT afterglow detection
  59. GRB 251208D: LAST optical upper limit
  60. GRB 251209A: Fermi GBM Final Real-time Localization
  61. GRB 251208D: LCO analysis of the XRT sources
  62. GRB 251208B: Fermi GBM Observation
  63. GRB 251208B: GROWTH-India Telescope optical upper limits
  64. GRB 251205A: J-band detection with WINTER
  65. GRB 251208D: Swift-XRT observations
  66. GRB 251208A: SVOM/GRM observation of a short burst
  67. GRB 251208C: SVOM/GRM observation of a short burst
  68. GRB 251129A: e-MERLIN C-band observations
  69. LAT GRB251208.43: Global MASTER-Net observations report
  70. GRB 251205A: Liverpool Telescope further optical follow-up observations
  71. GRB 251208D: LCO optical upper limits
  72. SVOM GRB251208D: Global MASTER-Net observations report
  73. GRB 251208B: Swift ToO observations
  74. GRB 251208B: Fermi-LAT detection
  75. GRB 251208B: Swift/BAT-GUANO arcminute localization of a burst
  76. GRB 251208D: SVOM possible detection of a faint burst
  77. GRB 251206A: SVOM detection of a burst through offline search
  78. GRB 251208C: Fermi GBM Final Real-time Localization
  79. GRB 251205A : MITSuME Akeno optical afterglow candidate detection
  80. GRB 251208B: Fermi GBM Final Real-time Localization
  81. GRB 251208A: Fermi GBM Final Real-time Localization
  82. GRB 251205A: FTW optical and NIR observations
  83. EP-WXT trigger 01709249380: KAIT confirmation of a stellar flare
  84. GRB 251205A: Liverpool Telescope further optical follow-up observations
  85. SVOM GRB251206.86: Global MASTER-Net observations report
  86. EP-WXT trigger 01709249380: confirmation of a stellar flare by BOOTES-5
  87. The EP-WXT trigger 01709249380 is likely a flaring star
  88. GRB 251205A: ZTF and ATLAS optical afterglow detections
  89. GRB 251205A: GROWTH-India Telescope optical observations
  90. GRB 251205A: Swift-BAT refined analysis
  91. GRB 251205A: Swift-XRT refined Analysis
  92. GRB 251205A: Swift/UVOT Detection
  93. GRB 251205A: Liverpool Telescope optical follow-up observations
  94. GRB 251203C: Swift/UVOT Upper Limit
  95. Konus-Wind detection of GRB 251118A
  96. GRB 251205A: Zeiss-1000 Koshka observatory optical observations
  97. GRB 251205A: COLIBRÍ optical observations
  98. GRB 251205A: GOTO optical afterglow detection
  99. GRB 251205A: NOT optical observations
  100. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100

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