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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. Swift GRB 251230A: Global MASTER-Net observations report
  2. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  3. EP251229a: Global MASTER-Net observations report
  4. EP251229a: Einstein Probe detection of an X-ray transient
  5. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  6. GRB 251226A: Glowbug gamma-ray detection
  7. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  8. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  9. Fermi GRB 251228A: Global MASTER-Net observations report
  10. The EP-WXT trigger 01709250662 is likely a flaring star
  11. GRB 251228A: Fermi GBM Final Real-time Localization
  12. GRB 251226A: SVOM/GRM observation
  13. GRB 251226A: GECAM-B detection
  14. SVOM GRB251227.07: Global MASTER-Net observations report
  15. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  16. The EP-WXT trigger 01709250617 is likely a flaring star
  17. IceCube Alert 251225.84: Global MASTER-Net observations report
  18. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  19. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  20. GRB 251222A: NUTTelA-TAO Early Measurements
  21. GRB 251222A/EP251222b: Optical detection with Kinder observations
  22. EP251222a: Optical upper limit with Kinder observations
  23. GRB 251221A: Swift-BAT refined analysis
  24. GRB 251222A/EP251222b: FTW optical and NIR observations
  25. EP251222a: FTW optical and NIR observations
  26. GRB 251205A: Kilonova-Catcher optical afterglow detection
  27. GRB 251222A: AbAO optical observations
  28. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  29. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  30. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  31. GRB 251222A: ZTSH BVRI optical observations
  32. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  33. GRB 251222A: Continued 1.3m DFOT optical observation
  34. EP251220a: 3.6m DOT optical afterglow detection
  35. GRB 251222A: Fermi GBM Observation
  36. EP251220a: CrAO ZTSh optical observations
  37. EP251221a: PRIME upper limit
  38. EP251222a: Global MASTER-Net observations report
  39. GRB 251222A / EP251222b: GECAM-B observation
  40. EP251221a: Liverpool Telescope upper limits
  41. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  42. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  43. Konus-Wind detection of GRB 251222A / EP251222b
  44. GRB 251222A: Swift-XRT afterglow detection
  45. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  46. EP251222a: NTT/ULTRACAM optical observations
  47. EP251222a: GOTO optical upper limit
  48. GRB 251222A / EP251222b: GOTO optical counterpart detection
  49. GRB 251222A / EP251222b: LCO optical observations
  50. GRB 251222A: 1.3m DFOT optical detection
  51. GRB251221A: 7DT optical upper limits
  52. EP251222a: GSP Optical Counterpart Detection
  53. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  54. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  55. EP251222b/GRB 251222A: SVOM/GRM observation
  56. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  57. EP251222a: Einstein Probe detection of an X-ray transient
  58. The EP-WXT trigger 01709250397 is likely a flaring star
  59. EP251221a: Global MASTER-Net observations report
  60. GRB 251222A: PRIME near-infrared detection
  61. EP251221a: NOT optical upper limit
  62. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  63. GRB 251222A: NOT optical observations
  64. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  65. IPN triangulation of GRB 251220B (short)
  66. GRB 251222A: Swift ToO observations
  67. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  68. GRB 251222A: SVOM/VT optical candidate
  69. GRB 251222A: SVOM detection of a long burst
  70. SVOM GRB251222A: Global MASTER-Net observations report
  71. GRB 251222A: Fermi GBM Final Real-time Localization
  72. EP251220a: PRIME upper limit
  73. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  74. GRB 251221A: PRIME near-infrared observation
  75. EP251220a: NOT optical observations
  76. EP251220a: FTW optical and NIR observations
  77. GRB 251221A: UAFO and Mondy optical upper limit
  78. GRB 251221A: Swift-XRT refined Analysis
  79. EP251221a: Einstein Probe detection of a fast X-ray transient
  80. GRB 251221A: Swift/UVOT Upper Limits
  81. Fermi Gamma-ray Burst Monitor trigger 788028118/251221696 is not a GRB
  82. GRB 251221A: Enhanced Swift-XRT position
  83. GRB 251221A: Fermi GBM Observation
  84. GRB 251221B: Fermi GBM Final Real-time Localization
  85. EP251220a: EP-FXT follow-up observation
  86. GRB 251220B: SVOM/GRM observation of a short burst
  87. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  88. EP 251220a: GOTO optical counterpart detection
  89. GRB 251221A: COLIBRÍ detection of the optical counterpart
  90. EP 251220a: COLIBRÍ detection of the optical counterpart
  91. GRB 251221A: Swift detection of a burst
  92. Swift GRB251221A: Global MASTER-Net observations report
  93. GRB 251221A: Fermi GBM Final Real-time Localization
  94. EP251220a: Global MASTER-Net observations report
  95. EP251220a: EP detection of a fast X-ray transient
  96. SVOM GRB251220.98: Global MASTER-Net observations report
  97. GRB 251220B: Fermi GBM Final Real-time Localization
  98. GRB 251219A: SVOM/GRM observation of a short burst
  99. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  100. Fermi-LAT Gamma-ray Observations of IceCube-251218A

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