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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. EP251229a: Global MASTER-Net observations report
  2. EP251229a: Einstein Probe detection of an X-ray transient
  3. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  4. GRB 251226A: Glowbug gamma-ray detection
  5. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  6. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  7. Fermi GRB 251228A: Global MASTER-Net observations report
  8. The EP-WXT trigger 01709250662 is likely a flaring star
  9. GRB 251228A: Fermi GBM Final Real-time Localization
  10. GRB 251226A: SVOM/GRM observation
  11. GRB 251226A: GECAM-B detection
  12. SVOM GRB251227.07: Global MASTER-Net observations report
  13. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  14. The EP-WXT trigger 01709250617 is likely a flaring star
  15. IceCube Alert 251225.84: Global MASTER-Net observations report
  16. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  17. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  18. GRB 251222A: NUTTelA-TAO Early Measurements
  19. GRB 251222A/EP251222b: Optical detection with Kinder observations
  20. EP251222a: Optical upper limit with Kinder observations
  21. GRB 251221A: Swift-BAT refined analysis
  22. GRB 251222A/EP251222b: FTW optical and NIR observations
  23. EP251222a: FTW optical and NIR observations
  24. GRB 251205A: Kilonova-Catcher optical afterglow detection
  25. GRB 251222A: AbAO optical observations
  26. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  27. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  28. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  29. GRB 251222A: ZTSH BVRI optical observations
  30. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  31. GRB 251222A: Continued 1.3m DFOT optical observation
  32. EP251220a: 3.6m DOT optical afterglow detection
  33. GRB 251222A: Fermi GBM Observation
  34. EP251220a: CrAO ZTSh optical observations
  35. EP251221a: PRIME upper limit
  36. EP251222a: Global MASTER-Net observations report
  37. GRB 251222A / EP251222b: GECAM-B observation
  38. EP251221a: Liverpool Telescope upper limits
  39. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  40. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  41. Konus-Wind detection of GRB 251222A / EP251222b
  42. GRB 251222A: Swift-XRT afterglow detection
  43. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  44. EP251222a: NTT/ULTRACAM optical observations
  45. EP251222a: GOTO optical upper limit
  46. GRB 251222A / EP251222b: GOTO optical counterpart detection
  47. GRB 251222A / EP251222b: LCO optical observations
  48. GRB 251222A: 1.3m DFOT optical detection
  49. GRB251221A: 7DT optical upper limits
  50. EP251222a: GSP Optical Counterpart Detection
  51. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  52. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  53. EP251222b/GRB 251222A: SVOM/GRM observation
  54. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  55. EP251222a: Einstein Probe detection of an X-ray transient
  56. The EP-WXT trigger 01709250397 is likely a flaring star
  57. EP251221a: Global MASTER-Net observations report
  58. GRB 251222A: PRIME near-infrared detection
  59. EP251221a: NOT optical upper limit
  60. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  61. GRB 251222A: NOT optical observations
  62. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  63. IPN triangulation of GRB 251220B (short)
  64. GRB 251222A: Swift ToO observations
  65. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  66. GRB 251222A: SVOM/VT optical candidate
  67. GRB 251222A: SVOM detection of a long burst
  68. SVOM GRB251222A: Global MASTER-Net observations report
  69. GRB 251222A: Fermi GBM Final Real-time Localization
  70. EP251220a: PRIME upper limit
  71. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  72. GRB 251221A: PRIME near-infrared observation
  73. EP251220a: NOT optical observations
  74. EP251220a: FTW optical and NIR observations
  75. GRB 251221A: UAFO and Mondy optical upper limit
  76. GRB 251221A: Swift-XRT refined Analysis
  77. EP251221a: Einstein Probe detection of a fast X-ray transient
  78. GRB 251221A: Swift/UVOT Upper Limits
  79. Fermi Gamma-ray Burst Monitor trigger 788028118/251221696 is not a GRB
  80. GRB 251221A: Enhanced Swift-XRT position
  81. GRB 251221A: Fermi GBM Observation
  82. GRB 251221B: Fermi GBM Final Real-time Localization
  83. EP251220a: EP-FXT follow-up observation
  84. GRB 251220B: SVOM/GRM observation of a short burst
  85. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  86. EP 251220a: GOTO optical counterpart detection
  87. GRB 251221A: COLIBRÍ detection of the optical counterpart
  88. EP 251220a: COLIBRÍ detection of the optical counterpart
  89. GRB 251221A: Swift detection of a burst
  90. Swift GRB251221A: Global MASTER-Net observations report
  91. GRB 251221A: Fermi GBM Final Real-time Localization
  92. EP251220a: Global MASTER-Net observations report
  93. EP251220a: EP detection of a fast X-ray transient
  94. SVOM GRB251220.98: Global MASTER-Net observations report
  95. GRB 251220B: Fermi GBM Final Real-time Localization
  96. GRB 251219A: SVOM/GRM observation of a short burst
  97. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  98. Fermi-LAT Gamma-ray Observations of IceCube-251218A
  99. GRB 251220A: MAXI/GSC detection
  100. GRB 251215A: Swift-XRT afterglow detection

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