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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 251222A / EP251222b: LCO detection of the optical counterpart
  2. EP251222a: NTT/ULTRACAM optical observations
  3. EP251222a: GOTO optical upper limit
  4. GRB 251222A / EP251222b: GOTO optical counterpart detection
  5. GRB 251222A / EP251222b: LCO optical observations
  6. GRB 251222A: 1.3m DFOT optical detection
  7. GRB251221A: 7DT optical upper limits
  8. EP251222a: GSP Optical Counterpart Detection
  9. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  10. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  11. EP251222b/GRB 251222A: SVOM/GRM observation
  12. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  13. EP251222a: Einstein Probe detection of an X-ray transient
  14. The EP-WXT trigger 01709250397 is likely a flaring star
  15. EP251221a: Global MASTER-Net observations report
  16. GRB 251222A: PRIME near-infrared detection
  17. EP251221a: NOT optical upper limit
  18. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  19. GRB 251222A: NOT optical observations
  20. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  21. IPN triangulation of GRB 251220B (short)
  22. GRB 251222A: Swift ToO observations
  23. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  24. GRB 251222A: SVOM/VT optical candidate
  25. GRB 251222A: SVOM detection of a long burst
  26. SVOM GRB251222A: Global MASTER-Net observations report
  27. GRB 251222A: Fermi GBM Final Real-time Localization
  28. EP251220a: PRIME upper limit
  29. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  30. GRB 251221A: PRIME near-infrared observation
  31. EP251220a: NOT optical observations
  32. EP251220a: FTW optical and NIR observations
  33. GRB 251221A: UAFO and Mondy optical upper limit
  34. GRB 251221A: Swift-XRT refined Analysis
  35. EP251221a: Einstein Probe detection of a fast X-ray transient
  36. GRB 251221A: Swift/UVOT Upper Limits
  37. Fermi Gamma-ray Burst Monitor trigger 788028118/251221696 is not a GRB
  38. GRB 251221A: Enhanced Swift-XRT position
  39. GRB 251221A: Fermi GBM Observation
  40. GRB 251221B: Fermi GBM Final Real-time Localization
  41. EP251220a: EP-FXT follow-up observation
  42. GRB 251220B: SVOM/GRM observation of a short burst
  43. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  44. EP 251220a: GOTO optical counterpart detection
  45. GRB 251221A: COLIBRÍ detection of the optical counterpart
  46. EP 251220a: COLIBRÍ detection of the optical counterpart
  47. GRB 251221A: Swift detection of a burst
  48. Swift GRB251221A: Global MASTER-Net observations report
  49. GRB 251221A: Fermi GBM Final Real-time Localization
  50. EP251220a: Global MASTER-Net observations report
  51. EP251220a: EP detection of a fast X-ray transient
  52. SVOM GRB251220.98: Global MASTER-Net observations report
  53. GRB 251220B: Fermi GBM Final Real-time Localization
  54. GRB 251219A: SVOM/GRM observation of a short burst
  55. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  56. Fermi-LAT Gamma-ray Observations of IceCube-251218A
  57. GRB 251220A: MAXI/GSC detection
  58. GRB 251215A: Swift-XRT afterglow detection
  59. IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
  60. IceCube-251218A: COLIBRÍ optical upper limits
  61. SVOM GRB251219.11: Global MASTER-Net observations report
  62. IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event
  63. IceCube Alert 251218.85: Global MASTER-Net observations report
  64. GRB 251214B: VIRT Optical Upper Limit
  65. Fermi trigger No 787736968: Global MASTER-Net observations report
  66. Fermi GRB 251217A: Global MASTER-Net observations report
  67. GRB 251217A: Fermi GBM Final Real-time Localization
  68. GRB 251215A: Swift/UVOT Upper LImits
  69. GRB 251215A: Fermi GBM Observation
  70. Fermi GRB 251216A: Global MASTER-Net observations report
  71. GRB 251202A/EP251202a: Koshka optical upper limit
  72. GRB 251214B: Mondy optical upper limit
  73. GRB 251215A: COLIBRÍ optical upper limit
  74. GRB 251216A: Fermi GBM Final Real-time Localization
  75. EP251214b: KAIT optical upper limit
  76. GRB 251215A: Swift-XRT observations
  77. Fermi GRB 251215A: Global MASTER-Net observations report
  78. EP251214a: Optical upper limit with Kinder observations
  79. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  80. GRB 251215A: Glowbug gamma-ray detection
  81. GRB 251214B: UAFO optical upper limit
  82. GRB 251214B: VLT/X-shooter observations
  83. GRB 251213A: GRID-10B observation
  84. GRB 251214B: Swift-BAT refined analysis
  85. GRB 251202A: radio detection with the VLA
  86. EP251214b: Global MASTER-Net observations report
  87. EP251214b : Einstein Probe detection of a fast X-ray transient
  88. EP251214b : Einstein Probe detection of a fast X-ray transient
  89. GRB 251214B: AbAO optical observations
  90. GRB 251214B: LCO detection of the optical counterpart
  91. GRB 251209A: GECAM-B observation of a long burst
  92. GRB 251214D: GECAM-B observation of a long burst
  93. GRB 251214B: Fermi GBM Observation
  94. GRB 251209A: Insight-HXMT/HE detection
  95. GRB 251215A: Swift ToO observations
  96. EP251214b (EP trigger 01709250023): LCO optical limits
  97. GRID detection of GRB 251213A
  98. GRB 251203B: AbAO optical observations
  99. GRB 251215A: Swift/BAT-GUANO arcminute localization of a burst
  100. GRB 251214B: GECAM-B observation of a long burst

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