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

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