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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"

41632 results found.

  1. GRB 260111A: COLIBRÍ optical afterglow candidate
  2. GRB 260111A: GECAM-B observation of a burst
  3. GRB 260111A: Fermi GBM Observation
  4. The EP-WXT trigger 01709251266 is likely a flaring star
  5. Swift Trigger 1434591 is not a GRB
  6. GRB 260111A: GOTO optical upper limits
  7. GRB 260112B: Fermi GBM Final Real-time Localization
  8. GRB 260111A: Swift ToO observations
  9. GRB 251230A: Mondy Optical Observations
  10. GRB 260111A: Swift/BAT-GUANO arcminute localization of a burst
  11. GRB 260112A: Fermi GBM Final Real-time Localization
  12. EP260110a: SVOM/VT optical upper limits
  13. IceCube-260111A - IceCube observation of a high-energy neutrino candidate track-like event
  14. IceCube Alert 260111A: Global MASTER-Net observations report
  15. EP260110a: Global MASTER-Net observations report
  16. Fermi GRB 260111A: Global MASTER-Net observations report
  17. GRB 260111A: Fermi GBM Final Real-time Localization
  18. Swift trigger 1436759 is not an astrophysical event
  19. EP260110a: KAIT optical upper limit
  20. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  21. EP 260110a: COLIBRÍ optical observations
  22. EP260110a: SVOM/C-GFT upper limit
  23. EP260110a: Einstein Probe detection of an X-ray transient
  24. GRB 260109C: LCO optical upper limits
  25. GRB 260109C: Kilonova-Catcher optical upper limit
  26. EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection
  27. Swift Trigger 1434591: possible GRB 260109C
  28. GRB 260109B: Fermi GBM Final Real-time Localization
  29. GRB 260102A: Swift-XRT afterglow detection
  30. GRB 260109A: Fermi GBM Final Real-time Localization
  31. GRB 260104A: Swift-BAT refined analysis
  32. GRB 260101A: Swift-BAT refined analysis
  33. Fermi GRB 260107A: Global MASTER-Net observations report
  34. GRB 260102A: AbAO optical observations
  35. GRB 260107A: Fermi GBM Final Real-time Localization
  36. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  37. The EP-WXT trigger 01709251112 is likely a flaring star
  38. Fermi GRB 260105A: Global MASTER-Net observations report
  39. GRB 260105B: Fermi GBM Detection
  40. EP260105a: FTW optical observations
  41. EP260104a: FTW optical observations
  42. GRB 260105B: BALROG localization (Fermi Trigger 789348101 / GRB 260105973)
  43. GRB 260105A: SVOM/GRM observation
  44. GRB 260105B: SVOM/GRM observation
  45. The EP-WXT trigger 01709251028 is likely a flaring star
  46. FRB 20251229A: COLIBRÍ optical upper limits
  47. Fermi GRB 260105B: Global MASTER-Net observations report
  48. EP260105a: SVOM/VT optical upperlimit
  49. GRB 260105B: Fermi GBM Final Real-time Localization
  50. GRB 260105A: Fermi GBM Final Real-time Localization
  51. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  52. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  53. EP260105a: LCO Optical Upper limit
  54. EP260104a: Global MASTER-Net observations report
  55. EP260104a: Einstein Probe detection of a fast X-ray transient
  56. GRB 260101A: COLIBRÍ optical upper limits
  57. EP260105a: Global MASTER-Net observations report
  58. EP260105a: Einstein Probe detection of an X-ray transient
  59. GRB 260103A: Insight-HXMT/HE detection
  60. GRB 260104A: COLIBRÍ optical upper limits
  61. GRB 260104C: Fermi GBM Final Real-time Localization
  62. Fermi GRB 260104B: Global MASTER-Net observations report
  63. Swift GRB 260104A: Global MASTER-Net observations report
  64. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  65. GRB 260104A: Swift-XRT refined Analysis
  66. GRB 260104A: Enhanced Swift-XRT position
  67. GRB 260101A: Swift/UVOT Detection
  68. GRB 260103A: GECAM-B observation of a burst
  69. GRB 260104B: Fermi GBM Final Localization
  70. GRB 260104A: Swift detection of a burst
  71. GRB 260103A: SVOM/GRM observation of a possible GRB
  72. Fermi-LAT Gamma-ray Observations of IceCube-251225A
  73. GRB 260101A: COLIBRÍ optical observations
  74. SVOM GRB260103.08: Global MASTER-Net observations report
  75. GRB 260102B: Fermi GBM Final Real-time Localization
  76. SVOM GRB260102A: Global MASTER-Net observations report
  77. Fermi GBM Sub-Threshold Detection of GRB 260102A
  78. GRB 260102A: EP-FXT follow-up observation
  79. EP260101a: Global MASTER-Net observations report
  80. GRB 260102A: LCO optical upper limits
  81. GRB 260102A: Swift-XRT observations
  82. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  83. GRB 251230A / EP251230a: GECAM-B detection
  84. GRB 260102A: SVOM/VT optical counterpart
  85. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  86. GRB 260102A: Swift ToO observations
  87. GRB 260101A: Fermi GBM Observation
  88. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  89. GRB 260102A: SVOM detection of a burst
  90. GRB 260101A: GECAM-B detection
  91. GRB 260101A: NOT spectroscopic observations
  92. GRB 260101A: SVOM/GRM observation
  93. GRB 260101A: Swift-XRT refined Analysis
  94. Swift GRB 260101A: Global MASTER-Net observations report
  95. GRB 260101A: Enhanced Swift-XRT position
  96. EP260101a: Einstein Probe detection of an X-ray transient
  97. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  98. GRB 260101A: LCO detection of the optical counterpart
  99. GRB 260101A: Swift detection of a burst with an optical counterpart
  100. GRB 260101A: Fermi GBM Final Real-time Localization

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