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

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