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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 251221B: Fermi GBM Final Real-time Localization
  2. EP251220a: EP-FXT follow-up observation
  3. GRB 251220B: SVOM/GRM observation of a short burst
  4. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  5. EP 251220a: GOTO optical counterpart detection
  6. GRB 251221A: COLIBRÍ detection of the optical counterpart
  7. EP 251220a: COLIBRÍ detection of the optical counterpart
  8. GRB 251221A: Swift detection of a burst
  9. Swift GRB251221A: Global MASTER-Net observations report
  10. GRB 251221A: Fermi GBM Final Real-time Localization
  11. EP251220a: Global MASTER-Net observations report
  12. EP251220a: EP detection of a fast X-ray transient
  13. SVOM GRB251220.98: Global MASTER-Net observations report
  14. GRB 251220B: Fermi GBM Final Real-time Localization
  15. GRB 251219A: SVOM/GRM observation of a short burst
  16. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  17. Fermi-LAT Gamma-ray Observations of IceCube-251218A
  18. GRB 251220A: MAXI/GSC detection
  19. GRB 251215A: Swift-XRT afterglow detection
  20. IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
  21. IceCube-251218A: COLIBRÍ optical upper limits
  22. SVOM GRB251219.11: Global MASTER-Net observations report
  23. IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event
  24. IceCube Alert 251218.85: Global MASTER-Net observations report
  25. GRB 251214B: VIRT Optical Upper Limit
  26. Fermi trigger No 787736968: Global MASTER-Net observations report
  27. Fermi GRB 251217A: Global MASTER-Net observations report
  28. GRB 251217A: Fermi GBM Final Real-time Localization
  29. GRB 251215A: Swift/UVOT Upper LImits
  30. GRB 251215A: Fermi GBM Observation
  31. Fermi GRB 251216A: Global MASTER-Net observations report
  32. GRB 251202A/EP251202a: Koshka optical upper limit
  33. GRB 251214B: Mondy optical upper limit
  34. GRB 251215A: COLIBRÍ optical upper limit
  35. GRB 251216A: Fermi GBM Final Real-time Localization
  36. EP251214b: KAIT optical upper limit
  37. GRB 251215A: Swift-XRT observations
  38. Fermi GRB 251215A: Global MASTER-Net observations report
  39. EP251214a: Optical upper limit with Kinder observations
  40. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  41. GRB 251215A: Glowbug gamma-ray detection
  42. GRB 251214B: UAFO optical upper limit
  43. GRB 251214B: VLT/X-shooter observations
  44. GRB 251213A: GRID-10B observation
  45. GRB 251214B: Swift-BAT refined analysis
  46. GRB 251202A: radio detection with the VLA
  47. EP251214b: Global MASTER-Net observations report
  48. EP251214b : Einstein Probe detection of a fast X-ray transient
  49. EP251214b : Einstein Probe detection of a fast X-ray transient
  50. GRB 251214B: AbAO optical observations
  51. GRB 251214B: LCO detection of the optical counterpart
  52. GRB 251209A: GECAM-B observation of a long burst
  53. GRB 251214D: GECAM-B observation of a long burst
  54. GRB 251214B: Fermi GBM Observation
  55. GRB 251209A: Insight-HXMT/HE detection
  56. GRB 251215A: Swift ToO observations
  57. EP251214b (EP trigger 01709250023): LCO optical limits
  58. GRID detection of GRB 251213A
  59. GRB 251203B: AbAO optical observations
  60. GRB 251215A: Swift/BAT-GUANO arcminute localization of a burst
  61. GRB 251214B: GECAM-B observation of a long burst
  62. GRB 251214B: Swift-XRT refined Analysis
  63. GRB 251213A: SVOM/GRM observation
  64. EP251214a: KAIT optical upper limit
  65. GRB 251214D: AstroSat CZTI detection of a long burst
  66. GRB 251213A: AstroSat CZTI detection
  67. GRB 251214A: AstroSat CZTI detection
  68. GRB 251213A: GECAM-B detection
  69. GRB 251214B: Swift/UVOT Detection
  70. GRB 251215A: Fermi GBM Final Real-time Localization
  71. GRB 251214B: COLIBRÍ observations of the afterglow
  72. EP251214a: EP-FXT non-detection and upper limit
  73. GRB 251214A: GECAM-B observation of a likely long burst
  74. GRB 251214B: 1.3m DFOT optical detection
  75. EP251214a: Global MASTER-Net observations report
  76. GRB 251214B: Enhanced Swift-XRT position
  77. GRB 251214B: Xinglong-2.16m optical observation
  78. GRB 251214C: Fermi GBM Final Localization
  79. GRB 251214B : MASTER optical afterglow detection
  80. Fermi trigger No 787396657: Global MASTER-Net observations report
  81. GRB 251214B: SVOM/C-GFT optical observations
  82. EP251214a: COLIBRÍ optical upper limit
  83. Swift GRB 251214B: Global MASTER-Net observations report
  84. EP251214.305: COLIBRÍ optical upper limit
  85. GRB 251214B: Swift detection of a burst with an optical counterpart
  86. GRB 251214B: Fermi GBM Final Real-time Localization
  87. EP251214a: EP-WXT detection of an X-ray transient possibly associated with GRB 251214A
  88. Fermi GRB 251214A: Global MASTER-Net observations report
  89. GRB 251214A: Fermi GBM Final Real-time Localization
  90. EP251212a: Global MASTER-Net observations report
  91. EP251212a: KAIT optical upper limit
  92. EP251212a / GRB 251212A: AstroSat CZTI detection
  93. EP251212a: EP-FXT follow-up observation
  94. GRB 251211B: AstroSat CZTI detection
  95. IceCube-251210A: No Candidate Transients from the Zwicky Transient Facility
  96. GRB 251209A: NuSTAR detection of prompt emission
  97. EP251212a : COLIBRÍ optical upper limit
  98. EP251212a: Einstein Probe detection of an X-ray transient
  99. Fermi-LAT Gamma-ray Observations of IceCube-251210A
  100. IceCube-251210A: Upper limits from a search for additional neutrino events in IceCube

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