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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. Fermi GRB 251216A: Global MASTER-Net observations report
  2. GRB 251202A/EP251202a: Koshka optical upper limit
  3. GRB 251214B: Mondy optical upper limit
  4. GRB 251215A: COLIBRÍ optical upper limit
  5. GRB 251216A: Fermi GBM Final Real-time Localization
  6. EP251214b: KAIT optical upper limit
  7. GRB 251215A: Swift-XRT observations
  8. Fermi GRB 251215A: Global MASTER-Net observations report
  9. EP251214a: Optical upper limit with Kinder observations
  10. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  11. GRB 251215A: Glowbug gamma-ray detection
  12. GRB 251214B: UAFO optical upper limit
  13. GRB 251214B: VLT/X-shooter observations
  14. GRB 251213A: GRID-10B observation
  15. GRB 251214B: Swift-BAT refined analysis
  16. GRB 251202A: radio detection with the VLA
  17. EP251214b: Global MASTER-Net observations report
  18. EP251214b : Einstein Probe detection of a fast X-ray transient
  19. EP251214b : Einstein Probe detection of a fast X-ray transient
  20. GRB 251214B: AbAO optical observations
  21. GRB 251214B: LCO detection of the optical counterpart
  22. GRB 251209A: GECAM-B observation of a long burst
  23. GRB 251214D: GECAM-B observation of a long burst
  24. GRB 251214B: Fermi GBM Observation
  25. GRB 251209A: Insight-HXMT/HE detection
  26. GRB 251215A: Swift ToO observations
  27. EP251214b (EP trigger 01709250023): LCO optical limits
  28. GRID detection of GRB 251213A
  29. GRB 251203B: AbAO optical observations
  30. GRB 251215A: Swift/BAT-GUANO arcminute localization of a burst
  31. GRB 251214B: GECAM-B observation of a long burst
  32. GRB 251214B: Swift-XRT refined Analysis
  33. GRB 251213A: SVOM/GRM observation
  34. EP251214a: KAIT optical upper limit
  35. GRB 251214D: AstroSat CZTI detection of a long burst
  36. GRB 251213A: AstroSat CZTI detection
  37. GRB 251214A: AstroSat CZTI detection
  38. GRB 251213A: GECAM-B detection
  39. GRB 251214B: Swift/UVOT Detection
  40. GRB 251215A: Fermi GBM Final Real-time Localization
  41. GRB 251214B: COLIBRÍ observations of the afterglow
  42. EP251214a: EP-FXT non-detection and upper limit
  43. GRB 251214A: GECAM-B observation of a likely long burst
  44. GRB 251214B: 1.3m DFOT optical detection
  45. EP251214a: Global MASTER-Net observations report
  46. GRB 251214B: Enhanced Swift-XRT position
  47. GRB 251214B: Xinglong-2.16m optical observation
  48. GRB 251214C: Fermi GBM Final Localization
  49. GRB 251214B : MASTER optical afterglow detection
  50. Fermi trigger No 787396657: Global MASTER-Net observations report
  51. GRB 251214B: SVOM/C-GFT optical observations
  52. EP251214a: COLIBRÍ optical upper limit
  53. Swift GRB 251214B: Global MASTER-Net observations report
  54. EP251214.305: COLIBRÍ optical upper limit
  55. GRB 251214B: Swift detection of a burst with an optical counterpart
  56. GRB 251214B: Fermi GBM Final Real-time Localization
  57. EP251214a: EP-WXT detection of an X-ray transient possibly associated with GRB 251214A
  58. Fermi GRB 251214A: Global MASTER-Net observations report
  59. GRB 251214A: Fermi GBM Final Real-time Localization
  60. EP251212a: Global MASTER-Net observations report
  61. EP251212a: KAIT optical upper limit
  62. EP251212a / GRB 251212A: AstroSat CZTI detection
  63. EP251212a: EP-FXT follow-up observation
  64. GRB 251211B: AstroSat CZTI detection
  65. IceCube-251210A: No Candidate Transients from the Zwicky Transient Facility
  66. GRB 251209A: NuSTAR detection of prompt emission
  67. EP251212a : COLIBRÍ optical upper limit
  68. EP251212a: Einstein Probe detection of an X-ray transient
  69. Fermi-LAT Gamma-ray Observations of IceCube-251210A
  70. IceCube-251210A: Upper limits from a search for additional neutrino events in IceCube
  71. Fermi GRB 251211B: Global MASTER-Net observations report
  72. GRB 251211B: Fermi GBM Final Real-time Localization
  73. IceCube-251210A: DDOTI Optical Upper Limit
  74. SVOM GRB251211.12: Global MASTER-Net observations report
  75. GRB 251211A: Fermi GBM Final Real-time Localization
  76. GRB 251209A: Fermi GBM observation
  77. GRB 251205A: 1.3m DFOT optical upper limit
  78. GRB 251209A: AstroSat CZTI detection
  79. IceCube Alert 251210.46: Global MASTER-Net observations report
  80. IceCube-251210A - IceCube observation of a high-energy neutrino candidate track-like event
  81. EP251124a: Mondy optical upper limit
  82. GRB 251129A/EP251129a: AbAO and Mondy optical observations
  83. EP251130a: Mondy and AbAO optical observations
  84. GRB 251208A: AstroSat CZTI detection
  85. Fermi GBM Sub-Threshold Detection of GRB 251205A
  86. GRB 251208A: Glowbug gamma-ray detection
  87. GRB 251208B: COLIBRÍ optical upper limits
  88. EP251118a / GRB 251118C: VLT/MUSE redshift confirmation
  89. GRB 251208C: GECAM-B observation of a short burst
  90. GRB 251208A: GECAM-B observation of a short burst
  91. Fermi GRB 251209A: Global MASTER-Net observations report
  92. Fermi GRB 251208C: Global MASTER-Net observations report
  93. GRB 251206A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  94. GRB 251208B: Swift-XRT afterglow detection
  95. GRB 251208D: LAST optical upper limit
  96. GRB 251209A: Fermi GBM Final Real-time Localization
  97. GRB 251208D: LCO analysis of the XRT sources
  98. GRB 251208B: Fermi GBM Observation
  99. GRB 251208B: GROWTH-India Telescope optical upper limits
  100. GRB 251205A: J-band detection with WINTER

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