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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: Optical detection with Kinder observations
  2. EP251222a: Optical upper limit with Kinder observations
  3. GRB 251221A: Swift-BAT refined analysis
  4. GRB 251222A/EP251222b: FTW optical and NIR observations
  5. EP251222a: FTW optical and NIR observations
  6. GRB 251205A: Kilonova-Catcher optical afterglow detection
  7. GRB 251222A: AbAO optical observations
  8. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  9. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  10. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  11. GRB 251222A: ZTSH BVRI optical observations
  12. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  13. GRB 251222A: Continued 1.3m DFOT optical observation
  14. EP251220a: 3.6m DOT optical afterglow detection
  15. GRB 251222A: Fermi GBM Observation
  16. EP251220a: CrAO ZTSh optical observations
  17. EP251221a: PRIME upper limit
  18. EP251222a: Global MASTER-Net observations report
  19. GRB 251222A / EP251222b: GECAM-B observation
  20. EP251221a: Liverpool Telescope upper limits
  21. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  22. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  23. Konus-Wind detection of GRB 251222A / EP251222b
  24. GRB 251222A: Swift-XRT afterglow detection
  25. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  26. EP251222a: NTT/ULTRACAM optical observations
  27. EP251222a: GOTO optical upper limit
  28. GRB 251222A / EP251222b: GOTO optical counterpart detection
  29. GRB 251222A / EP251222b: LCO optical observations
  30. GRB 251222A: 1.3m DFOT optical detection
  31. GRB251221A: 7DT optical upper limits
  32. EP251222a: GSP Optical Counterpart Detection
  33. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  34. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  35. EP251222b/GRB 251222A: SVOM/GRM observation
  36. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  37. EP251222a: Einstein Probe detection of an X-ray transient
  38. The EP-WXT trigger 01709250397 is likely a flaring star
  39. EP251221a: Global MASTER-Net observations report
  40. GRB 251222A: PRIME near-infrared detection
  41. EP251221a: NOT optical upper limit
  42. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  43. GRB 251222A: NOT optical observations
  44. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  45. IPN triangulation of GRB 251220B (short)
  46. GRB 251222A: Swift ToO observations
  47. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  48. GRB 251222A: SVOM/VT optical candidate
  49. GRB 251222A: SVOM detection of a long burst
  50. SVOM GRB251222A: Global MASTER-Net observations report
  51. GRB 251222A: Fermi GBM Final Real-time Localization
  52. EP251220a: PRIME upper limit
  53. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  54. GRB 251221A: PRIME near-infrared observation
  55. EP251220a: NOT optical observations
  56. EP251220a: FTW optical and NIR observations
  57. GRB 251221A: UAFO and Mondy optical upper limit
  58. GRB 251221A: Swift-XRT refined Analysis
  59. EP251221a: Einstein Probe detection of a fast X-ray transient
  60. GRB 251221A: Swift/UVOT Upper Limits
  61. Fermi Gamma-ray Burst Monitor trigger 788028118/251221696 is not a GRB
  62. GRB 251221A: Enhanced Swift-XRT position
  63. GRB 251221A: Fermi GBM Observation
  64. GRB 251221B: Fermi GBM Final Real-time Localization
  65. EP251220a: EP-FXT follow-up observation
  66. GRB 251220B: SVOM/GRM observation of a short burst
  67. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  68. EP 251220a: GOTO optical counterpart detection
  69. GRB 251221A: COLIBRÍ detection of the optical counterpart
  70. EP 251220a: COLIBRÍ detection of the optical counterpart
  71. GRB 251221A: Swift detection of a burst
  72. Swift GRB251221A: Global MASTER-Net observations report
  73. GRB 251221A: Fermi GBM Final Real-time Localization
  74. EP251220a: Global MASTER-Net observations report
  75. EP251220a: EP detection of a fast X-ray transient
  76. SVOM GRB251220.98: Global MASTER-Net observations report
  77. GRB 251220B: Fermi GBM Final Real-time Localization
  78. GRB 251219A: SVOM/GRM observation of a short burst
  79. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  80. Fermi-LAT Gamma-ray Observations of IceCube-251218A
  81. GRB 251220A: MAXI/GSC detection
  82. GRB 251215A: Swift-XRT afterglow detection
  83. IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
  84. IceCube-251218A: COLIBRÍ optical upper limits
  85. SVOM GRB251219.11: Global MASTER-Net observations report
  86. IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event
  87. IceCube Alert 251218.85: Global MASTER-Net observations report
  88. GRB 251214B: VIRT Optical Upper Limit
  89. Fermi trigger No 787736968: Global MASTER-Net observations report
  90. Fermi GRB 251217A: Global MASTER-Net observations report
  91. GRB 251217A: Fermi GBM Final Real-time Localization
  92. GRB 251215A: Swift/UVOT Upper LImits
  93. GRB 251215A: Fermi GBM Observation
  94. Fermi GRB 251216A: Global MASTER-Net observations report
  95. GRB 251202A/EP251202a: Koshka optical upper limit
  96. GRB 251214B: Mondy optical upper limit
  97. GRB 251215A: COLIBRÍ optical upper limit
  98. GRB 251216A: Fermi GBM Final Real-time Localization
  99. EP251214b: KAIT optical upper limit
  100. GRB 251215A: Swift-XRT observations

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