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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. Fermi trigger No 802141998: Global MASTER-Net observations report
  2. EP260602a: SVOM/VT optical magnitudes correction
  3. GRB 260601A: SVOM/GRM observation of a short burst
  4. EP260602c: Einstein Probe detection of a fast X-ray transient
  5. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  6. EP260602a: COLIBRÍ optical observations
  7. GRB260601B/EP260601a: NOT near-infrared observations
  8. SVOM GRB260603.23: Global MASTER-Net observations report
  9. GRB 260603A: SVOM detection of a burst
  10. EP260602b: Einstein Probe detection of a fast X-ray transient
  11. GRB 260601B/EP260601a: Insight-HXMT detection
  12. Fermi GRB 260602B: Global MASTER-Net observations report
  13. Fermi GRB 260602B: Global MASTER-Net observations report
  14. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  15. EP260602a: SVOM/VT optical candidate
  16. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  17. GRB 260602B: Fermi GBM Final Localization
  18. GRB 260601A: GECAM-B observation of a short burst
  19. GRB 260601B/EP260601a: J-band upper limit with WINTER
  20. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  21. EP260530a/AT 2026nwl: KAIT optical observations
  22. GRB 260602A: Fermi GBM Final Real-time Localization
  23. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  24. EP260602a: Optical upper limits with Kinder observations
  25. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  26. EP260602a: Einstein Probe detection of a fast X-ray transient
  27. GRB 260601B/EP260601a: SVOM/VT optical observations
  28. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  29. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  30. EP260601a: Einstein Probe detection of an X-ray transient
  31. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  32. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  33. GRB 260601A: Glowbug gamma-ray detection of a short burst
  34. GRB 260531B: Glowbug gamma-ray detection
  35. GRB 260516D: VLA radio detection
  36. GRB 260601A: Fermi GBM Observation
  37. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  38. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  39. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  40. Fermi GRB 260601A: Global MASTER-Net observations report
  41. GRB 260601A: Fermi GBM Final Real-time Localization
  42. GRB 260531B: GECAM-B observation
  43. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  44. The EP-WXT trigger 01709266272 is likely a flaring star
  45. GRB 260531C: Fermi GBM Final Localization Correction
  46. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  47. AT2026nik: EP-FXT X-ray counterpart
  48. Fermi trigger No 801900520: Global MASTER-Net observations report
  49. GRB 260531B: Fermi GBM Final Real-time Localization
  50. GRB 260531A: MAXI/GSC detection
  51. AT 2026nuz: COLIBRÍ optical observations
  52. IPN triangulation of GRB 260527A / EP260527a
  53. EP260527a/GRB 260527A: further FTW optical and NIR observations
  54. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  55. GRB 260530A: Fermi GBM Final Real-time Localization
  56. GRB 260527A / EP260527a: VLA radio detection
  57. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  58. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  59. GRB 260529A: GOTO tentative optical afterglow candidate
  60. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  61. GRB 260527A/EP260527a: Insight-HXMT detection
  62. Fermi GRB 260529A: Global MASTER-Net observations report
  63. GRB 260529A: Fermi GBM Final Real-time Localization
  64. EP260526a: SVOM/VT optical upper limits
  65. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  66. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  67. EP260527a / GRB 260527A: NOT optical observations
  68. GRB 260527A/EP260527a: FTW optical and NIR observations
  69. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  70. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  71. EP260527a/GRB 260527A: EP-FXT follow-up observation
  72. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  73. GRB 260526A: GECAM-B observation
  74. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  75. EP260526a: EP-FXT follow-up observation
  76. EP260527a: SVOM/VT optical observation
  77. EP260527a: COLIBRÍ optical detection
  78. EP260527a: Einstein Probe detection of a fast X-ray transient
  79. The EP-WXT trigger 01709266172 is likely a flaring star
  80. The EP-WXT trigger 01709266147 is likely a flaring star
  81. Fermi trigger No 801580882: Global MASTER-Net observations report
  82. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  83. EP260526a: LCO optical upper limits
  84. EP260526a: Einstein Probe detection of a fast X-ray transient
  85. GRB 260525A: AstroSat CZTI detection
  86. EP260526.405: COLIBRÍ optical upper limits
  87. The EP-WXT trigger 01709266106 is not a real source
  88. Fermi GRB 260526A: Global MASTER-Net observations report
  89. GRB 260526A: Fermi GBM Final Real-time Localization
  90. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  91. EP-WXT 01709266106: NOT optical upper limits
  92. Fermi GRB 260525A: Global MASTER-Net observations report
  93. GRB 260525A: Fermi GBM Final Real-time Localization
  94. GRB 260523B: AstroSat CZTI detection
  95. GRB 260523B: GECAM-B observation
  96. Fermi GRB 260523A: Global MASTER-Net observations report
  97. GRB 260523B: Fermi GBM Final Real-time Localization
  98. GRB 260523A: Fermi GBM Final Real-time Localization
  99. GRB 260522A: Fermi GBM Observation
  100. GRB 260522B: NuSTAR detection of prompt emission

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