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

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