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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. EP251220a: 3.6m DOT optical afterglow detection
  2. GRB 251222A: Fermi GBM Observation
  3. EP251220a: CrAO ZTSh optical observations
  4. EP251221a: PRIME upper limit
  5. EP251222a: Global MASTER-Net observations report
  6. GRB 251222A / EP251222b: GECAM-B observation
  7. EP251221a: Liverpool Telescope upper limits
  8. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  9. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  10. Konus-Wind detection of GRB 251222A / EP251222b
  11. GRB 251222A: Swift-XRT afterglow detection
  12. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  13. EP251222a: NTT/ULTRACAM optical observations
  14. EP251222a: GOTO optical upper limit
  15. GRB 251222A / EP251222b: GOTO optical counterpart detection
  16. GRB 251222A / EP251222b: LCO optical observations
  17. GRB 251222A: 1.3m DFOT optical detection
  18. GRB251221A: 7DT optical upper limits
  19. EP251222a: GSP Optical Counterpart Detection
  20. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  21. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  22. EP251222b/GRB 251222A: SVOM/GRM observation
  23. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  24. EP251222a: Einstein Probe detection of an X-ray transient
  25. The EP-WXT trigger 01709250397 is likely a flaring star
  26. EP251221a: Global MASTER-Net observations report
  27. GRB 251222A: PRIME near-infrared detection
  28. EP251221a: NOT optical upper limit
  29. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  30. GRB 251222A: NOT optical observations
  31. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  32. IPN triangulation of GRB 251220B (short)
  33. GRB 251222A: Swift ToO observations
  34. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  35. GRB 251222A: SVOM/VT optical candidate
  36. GRB 251222A: SVOM detection of a long burst
  37. SVOM GRB251222A: Global MASTER-Net observations report
  38. GRB 251222A: Fermi GBM Final Real-time Localization
  39. EP251220a: PRIME upper limit
  40. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  41. GRB 251221A: PRIME near-infrared observation
  42. EP251220a: NOT optical observations
  43. EP251220a: FTW optical and NIR observations
  44. GRB 251221A: UAFO and Mondy optical upper limit
  45. GRB 251221A: Swift-XRT refined Analysis
  46. EP251221a: Einstein Probe detection of a fast X-ray transient
  47. GRB 251221A: Swift/UVOT Upper Limits
  48. Fermi Gamma-ray Burst Monitor trigger 788028118/251221696 is not a GRB
  49. GRB 251221A: Enhanced Swift-XRT position
  50. GRB 251221A: Fermi GBM Observation
  51. GRB 251221B: Fermi GBM Final Real-time Localization
  52. EP251220a: EP-FXT follow-up observation
  53. GRB 251220B: SVOM/GRM observation of a short burst
  54. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  55. EP 251220a: GOTO optical counterpart detection
  56. GRB 251221A: COLIBRÍ detection of the optical counterpart
  57. EP 251220a: COLIBRÍ detection of the optical counterpart
  58. GRB 251221A: Swift detection of a burst
  59. Swift GRB251221A: Global MASTER-Net observations report
  60. GRB 251221A: Fermi GBM Final Real-time Localization
  61. EP251220a: Global MASTER-Net observations report
  62. EP251220a: EP detection of a fast X-ray transient
  63. SVOM GRB251220.98: Global MASTER-Net observations report
  64. GRB 251220B: Fermi GBM Final Real-time Localization
  65. GRB 251219A: SVOM/GRM observation of a short burst
  66. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  67. Fermi-LAT Gamma-ray Observations of IceCube-251218A
  68. GRB 251220A: MAXI/GSC detection
  69. GRB 251215A: Swift-XRT afterglow detection
  70. IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
  71. IceCube-251218A: COLIBRÍ optical upper limits
  72. SVOM GRB251219.11: Global MASTER-Net observations report
  73. IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event
  74. IceCube Alert 251218.85: Global MASTER-Net observations report
  75. GRB 251214B: VIRT Optical Upper Limit
  76. Fermi trigger No 787736968: Global MASTER-Net observations report
  77. Fermi GRB 251217A: Global MASTER-Net observations report
  78. GRB 251217A: Fermi GBM Final Real-time Localization
  79. GRB 251215A: Swift/UVOT Upper LImits
  80. GRB 251215A: Fermi GBM Observation
  81. Fermi GRB 251216A: Global MASTER-Net observations report
  82. GRB 251202A/EP251202a: Koshka optical upper limit
  83. GRB 251214B: Mondy optical upper limit
  84. GRB 251215A: COLIBRÍ optical upper limit
  85. GRB 251216A: Fermi GBM Final Real-time Localization
  86. EP251214b: KAIT optical upper limit
  87. GRB 251215A: Swift-XRT observations
  88. Fermi GRB 251215A: Global MASTER-Net observations report
  89. EP251214a: Optical upper limit with Kinder observations
  90. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  91. GRB 251215A: Glowbug gamma-ray detection
  92. GRB 251214B: UAFO optical upper limit
  93. GRB 251214B: VLT/X-shooter observations
  94. GRB 251213A: GRID-10B observation
  95. GRB 251214B: Swift-BAT refined analysis
  96. GRB 251202A: radio detection with the VLA
  97. EP251214b: Global MASTER-Net observations report
  98. EP251214b : Einstein Probe detection of a fast X-ray transient
  99. EP251214b : Einstein Probe detection of a fast X-ray transient
  100. GRB 251214B: AbAO optical observations

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