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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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. GRB 260604C: Fermi GBM Final Real-time Localization
  2. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  3. GRB 260603A: NOT optical observations
  4. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  5. GRB 260604B: Fermi GBM Final Real-time Localization
  6. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  7. EP260602a: EP-FXT follow-up observation
  8. EP260603a: Global MASTER-Net observations report
  9. EP260603a: Einstein Probe detection of a fast X-ray transient
  10. EP260602d: Optical Upper limits with kinder observations
  11. GRB 260604A: Fermi GBM Final Real-time Localization
  12. EP260602b: Liverpool Telescope observations
  13. EP260602a: Liverpool Telescope optical upper limits
  14. EP260602b: Liverpool Telescope and LCO observations
  15. GRB 260603B: Fermi GBM Final Localization
  16. EP260602a: GTC and Liverpool Telescope optical observations
  17. Konus-Wind detection of GRB 260601B/EP260601a
  18. GRB 260603A: EP-FXT follow-up observation
  19. EP260601a/GRB 260601B: EP-FXT follow-up observation
  20. GRB 260601B / EP260601a: Mondy optical upper limit
  21. EP260602b: EP-FXT follow-up observation
  22. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  23. GRB 260603A: Kilonova-Catcher optical upper limit
  24. GRB 260603A: SVOM/VT optical observations
  25. EP260602a: NOT NIR J-band observations
  26. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  27. EP260602d: Einstein Probe detection of a fast X-ray transient
  28. Fermi trigger No 802141998: Global MASTER-Net observations report
  29. EP260602a: SVOM/VT optical magnitudes correction
  30. GRB 260601A: SVOM/GRM observation of a short burst
  31. EP260602c: Einstein Probe detection of a fast X-ray transient
  32. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  33. EP260602a: COLIBRÍ optical observations
  34. GRB260601B/EP260601a: NOT near-infrared observations
  35. SVOM GRB260603.23: Global MASTER-Net observations report
  36. GRB 260603A: SVOM detection of a burst
  37. EP260602b: Einstein Probe detection of a fast X-ray transient
  38. GRB 260601B/EP260601a: Insight-HXMT detection
  39. Fermi GRB 260602B: Global MASTER-Net observations report
  40. Fermi GRB 260602B: Global MASTER-Net observations report
  41. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  42. EP260602a: SVOM/VT optical candidate
  43. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  44. GRB 260602B: Fermi GBM Final Localization
  45. GRB 260601A: GECAM-B observation of a short burst
  46. GRB 260601B/EP260601a: J-band upper limit with WINTER
  47. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  48. EP260530a/AT 2026nwl: KAIT optical observations
  49. GRB 260602A: Fermi GBM Final Real-time Localization
  50. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  51. EP260602a: Optical upper limits with Kinder observations
  52. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  53. EP260602a: Einstein Probe detection of a fast X-ray transient
  54. GRB 260601B/EP260601a: SVOM/VT optical observations
  55. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  56. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  57. EP260601a: Einstein Probe detection of an X-ray transient
  58. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  59. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  60. GRB 260601A: Glowbug gamma-ray detection of a short burst
  61. GRB 260531B: Glowbug gamma-ray detection
  62. GRB 260516D: VLA radio detection
  63. GRB 260601A: Fermi GBM Observation
  64. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  65. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  66. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  67. Fermi GRB 260601A: Global MASTER-Net observations report
  68. GRB 260601A: Fermi GBM Final Real-time Localization
  69. GRB 260531B: GECAM-B observation
  70. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  71. The EP-WXT trigger 01709266272 is likely a flaring star
  72. GRB 260531C: Fermi GBM Final Localization Correction
  73. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  74. AT2026nik: EP-FXT X-ray counterpart
  75. Fermi trigger No 801900520: Global MASTER-Net observations report
  76. GRB 260531B: Fermi GBM Final Real-time Localization
  77. GRB 260531A: MAXI/GSC detection
  78. AT 2026nuz: COLIBRÍ optical observations
  79. IPN triangulation of GRB 260527A / EP260527a
  80. EP260527a/GRB 260527A: further FTW optical and NIR observations
  81. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  82. GRB 260530A: Fermi GBM Final Real-time Localization
  83. GRB 260527A / EP260527a: VLA radio detection
  84. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  85. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  86. GRB 260529A: GOTO tentative optical afterglow candidate
  87. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  88. GRB 260527A/EP260527a: Insight-HXMT detection
  89. Fermi GRB 260529A: Global MASTER-Net observations report
  90. GRB 260529A: Fermi GBM Final Real-time Localization
  91. EP260526a: SVOM/VT optical upper limits
  92. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  93. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  94. EP260527a / GRB 260527A: NOT optical observations
  95. GRB 260527A/EP260527a: FTW optical and NIR observations
  96. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  97. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  98. EP260527a/GRB 260527A: EP-FXT follow-up observation
  99. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  100. GRB 260526A: GECAM-B observation

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