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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 251221A: Swift-XRT refined Analysis
  2. EP251221a: Einstein Probe detection of a fast X-ray transient
  3. GRB 251221A: Swift/UVOT Upper Limits
  4. Fermi Gamma-ray Burst Monitor trigger 788028118/251221696 is not a GRB
  5. GRB 251221A: Enhanced Swift-XRT position
  6. GRB 251221A: Fermi GBM Observation
  7. GRB 251221B: Fermi GBM Final Real-time Localization
  8. EP251220a: EP-FXT follow-up observation
  9. GRB 251220B: SVOM/GRM observation of a short burst
  10. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  11. EP 251220a: GOTO optical counterpart detection
  12. GRB 251221A: COLIBRÍ detection of the optical counterpart
  13. EP 251220a: COLIBRÍ detection of the optical counterpart
  14. GRB 251221A: Swift detection of a burst
  15. Swift GRB251221A: Global MASTER-Net observations report
  16. GRB 251221A: Fermi GBM Final Real-time Localization
  17. EP251220a: Global MASTER-Net observations report
  18. EP251220a: EP detection of a fast X-ray transient
  19. SVOM GRB251220.98: Global MASTER-Net observations report
  20. GRB 251220B: Fermi GBM Final Real-time Localization
  21. GRB 251219A: SVOM/GRM observation of a short burst
  22. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  23. Fermi-LAT Gamma-ray Observations of IceCube-251218A
  24. GRB 251220A: MAXI/GSC detection
  25. GRB 251215A: Swift-XRT afterglow detection
  26. IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
  27. IceCube-251218A: COLIBRÍ optical upper limits
  28. SVOM GRB251219.11: Global MASTER-Net observations report
  29. IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event
  30. IceCube Alert 251218.85: Global MASTER-Net observations report
  31. GRB 251214B: VIRT Optical Upper Limit
  32. Fermi trigger No 787736968: Global MASTER-Net observations report
  33. Fermi GRB 251217A: Global MASTER-Net observations report
  34. GRB 251217A: Fermi GBM Final Real-time Localization
  35. GRB 251215A: Swift/UVOT Upper LImits
  36. GRB 251215A: Fermi GBM Observation
  37. Fermi GRB 251216A: Global MASTER-Net observations report
  38. GRB 251202A/EP251202a: Koshka optical upper limit
  39. GRB 251214B: Mondy optical upper limit
  40. GRB 251215A: COLIBRÍ optical upper limit
  41. GRB 251216A: Fermi GBM Final Real-time Localization
  42. EP251214b: KAIT optical upper limit
  43. GRB 251215A: Swift-XRT observations
  44. Fermi GRB 251215A: Global MASTER-Net observations report
  45. EP251214a: Optical upper limit with Kinder observations
  46. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  47. GRB 251215A: Glowbug gamma-ray detection
  48. GRB 251214B: UAFO optical upper limit
  49. GRB 251214B: VLT/X-shooter observations
  50. GRB 251213A: GRID-10B observation
  51. GRB 251214B: Swift-BAT refined analysis
  52. GRB 251202A: radio detection with the VLA
  53. EP251214b: Global MASTER-Net observations report
  54. EP251214b : Einstein Probe detection of a fast X-ray transient
  55. EP251214b : Einstein Probe detection of a fast X-ray transient
  56. GRB 251214B: AbAO optical observations
  57. GRB 251214B: LCO detection of the optical counterpart
  58. GRB 251209A: GECAM-B observation of a long burst
  59. GRB 251214D: GECAM-B observation of a long burst
  60. GRB 251214B: Fermi GBM Observation
  61. GRB 251209A: Insight-HXMT/HE detection
  62. GRB 251215A: Swift ToO observations
  63. EP251214b (EP trigger 01709250023): LCO optical limits
  64. GRID detection of GRB 251213A
  65. GRB 251203B: AbAO optical observations
  66. GRB 251215A: Swift/BAT-GUANO arcminute localization of a burst
  67. GRB 251214B: GECAM-B observation of a long burst
  68. GRB 251214B: Swift-XRT refined Analysis
  69. GRB 251213A: SVOM/GRM observation
  70. EP251214a: KAIT optical upper limit
  71. GRB 251214D: AstroSat CZTI detection of a long burst
  72. GRB 251213A: AstroSat CZTI detection
  73. GRB 251214A: AstroSat CZTI detection
  74. GRB 251213A: GECAM-B detection
  75. GRB 251214B: Swift/UVOT Detection
  76. GRB 251215A: Fermi GBM Final Real-time Localization
  77. GRB 251214B: COLIBRÍ observations of the afterglow
  78. EP251214a: EP-FXT non-detection and upper limit
  79. GRB 251214A: GECAM-B observation of a likely long burst
  80. GRB 251214B: 1.3m DFOT optical detection
  81. EP251214a: Global MASTER-Net observations report
  82. GRB 251214B: Enhanced Swift-XRT position
  83. GRB 251214B: Xinglong-2.16m optical observation
  84. GRB 251214C: Fermi GBM Final Localization
  85. GRB 251214B : MASTER optical afterglow detection
  86. Fermi trigger No 787396657: Global MASTER-Net observations report
  87. GRB 251214B: SVOM/C-GFT optical observations
  88. EP251214a: COLIBRÍ optical upper limit
  89. Swift GRB 251214B: Global MASTER-Net observations report
  90. EP251214.305: COLIBRÍ optical upper limit
  91. GRB 251214B: Swift detection of a burst with an optical counterpart
  92. GRB 251214B: Fermi GBM Final Real-time Localization
  93. EP251214a: EP-WXT detection of an X-ray transient possibly associated with GRB 251214A
  94. Fermi GRB 251214A: Global MASTER-Net observations report
  95. GRB 251214A: Fermi GBM Final Real-time Localization
  96. EP251212a: Global MASTER-Net observations report
  97. EP251212a: KAIT optical upper limit
  98. EP251212a / GRB 251212A: AstroSat CZTI detection
  99. EP251212a: EP-FXT follow-up observation
  100. GRB 251211B: AstroSat CZTI detection

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