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

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