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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. IceCube Alert 251225.84: Global MASTER-Net observations report
  2. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  3. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  4. GRB 251222A: NUTTelA-TAO Early Measurements
  5. GRB 251222A/EP251222b: Optical detection with Kinder observations
  6. EP251222a: Optical upper limit with Kinder observations
  7. GRB 251221A: Swift-BAT refined analysis
  8. GRB 251222A/EP251222b: FTW optical and NIR observations
  9. EP251222a: FTW optical and NIR observations
  10. GRB 251205A: Kilonova-Catcher optical afterglow detection
  11. GRB 251222A: AbAO optical observations
  12. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  13. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  14. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  15. GRB 251222A: ZTSH BVRI optical observations
  16. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  17. GRB 251222A: Continued 1.3m DFOT optical observation
  18. EP251220a: 3.6m DOT optical afterglow detection
  19. GRB 251222A: Fermi GBM Observation
  20. EP251220a: CrAO ZTSh optical observations
  21. EP251221a: PRIME upper limit
  22. EP251222a: Global MASTER-Net observations report
  23. GRB 251222A / EP251222b: GECAM-B observation
  24. EP251221a: Liverpool Telescope upper limits
  25. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  26. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  27. Konus-Wind detection of GRB 251222A / EP251222b
  28. GRB 251222A: Swift-XRT afterglow detection
  29. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  30. EP251222a: NTT/ULTRACAM optical observations
  31. EP251222a: GOTO optical upper limit
  32. GRB 251222A / EP251222b: GOTO optical counterpart detection
  33. GRB 251222A / EP251222b: LCO optical observations
  34. GRB 251222A: 1.3m DFOT optical detection
  35. GRB251221A: 7DT optical upper limits
  36. EP251222a: GSP Optical Counterpart Detection
  37. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  38. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  39. EP251222b/GRB 251222A: SVOM/GRM observation
  40. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  41. EP251222a: Einstein Probe detection of an X-ray transient
  42. The EP-WXT trigger 01709250397 is likely a flaring star
  43. EP251221a: Global MASTER-Net observations report
  44. GRB 251222A: PRIME near-infrared detection
  45. EP251221a: NOT optical upper limit
  46. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  47. GRB 251222A: NOT optical observations
  48. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  49. IPN triangulation of GRB 251220B (short)
  50. GRB 251222A: Swift ToO observations
  51. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  52. GRB 251222A: SVOM/VT optical candidate
  53. GRB 251222A: SVOM detection of a long burst
  54. SVOM GRB251222A: Global MASTER-Net observations report
  55. GRB 251222A: Fermi GBM Final Real-time Localization
  56. EP251220a: PRIME upper limit
  57. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  58. GRB 251221A: PRIME near-infrared observation
  59. EP251220a: NOT optical observations
  60. EP251220a: FTW optical and NIR observations
  61. GRB 251221A: UAFO and Mondy optical upper limit
  62. GRB 251221A: Swift-XRT refined Analysis
  63. EP251221a: Einstein Probe detection of a fast X-ray transient
  64. GRB 251221A: Swift/UVOT Upper Limits
  65. Fermi Gamma-ray Burst Monitor trigger 788028118/251221696 is not a GRB
  66. GRB 251221A: Enhanced Swift-XRT position
  67. GRB 251221A: Fermi GBM Observation
  68. GRB 251221B: Fermi GBM Final Real-time Localization
  69. EP251220a: EP-FXT follow-up observation
  70. GRB 251220B: SVOM/GRM observation of a short burst
  71. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  72. EP 251220a: GOTO optical counterpart detection
  73. GRB 251221A: COLIBRÍ detection of the optical counterpart
  74. EP 251220a: COLIBRÍ detection of the optical counterpart
  75. GRB 251221A: Swift detection of a burst
  76. Swift GRB251221A: Global MASTER-Net observations report
  77. GRB 251221A: Fermi GBM Final Real-time Localization
  78. EP251220a: Global MASTER-Net observations report
  79. EP251220a: EP detection of a fast X-ray transient
  80. SVOM GRB251220.98: Global MASTER-Net observations report
  81. GRB 251220B: Fermi GBM Final Real-time Localization
  82. GRB 251219A: SVOM/GRM observation of a short burst
  83. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  84. Fermi-LAT Gamma-ray Observations of IceCube-251218A
  85. GRB 251220A: MAXI/GSC detection
  86. GRB 251215A: Swift-XRT afterglow detection
  87. IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
  88. IceCube-251218A: COLIBRÍ optical upper limits
  89. SVOM GRB251219.11: Global MASTER-Net observations report
  90. IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event
  91. IceCube Alert 251218.85: Global MASTER-Net observations report
  92. GRB 251214B: VIRT Optical Upper Limit
  93. Fermi trigger No 787736968: Global MASTER-Net observations report
  94. Fermi GRB 251217A: Global MASTER-Net observations report
  95. GRB 251217A: Fermi GBM Final Real-time Localization
  96. GRB 251215A: Swift/UVOT Upper LImits
  97. GRB 251215A: Fermi GBM Observation
  98. Fermi GRB 251216A: Global MASTER-Net observations report
  99. GRB 251202A/EP251202a: Koshka optical upper limit
  100. GRB 251214B: Mondy optical upper limit

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