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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: GOTO detections of the optical afterglow
  2. GRB 260604C: Correction to GCN 44828
  3. GRB 260604C: Kilonova-Catcher optical afterglow detection
  4. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  5. The EP-WXT trigger 01709266798 is likely a flaring star
  6. GRB 260604C: Jinshan optical observations
  7. GRB 260604C: Fermi GBM Observation
  8. EP260602d: J-band upper limit with WINTER
  9. EP260602b: J-band upper limit with WINTER
  10. GRB 260604C: LAST detection of optical counterpart candidate
  11. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  12. Fermi GRB 260604C: Global MASTER-Net observations report
  13. Fermi GRB 260604C: Global MASTER-Net observations report
  14. SVOM GRB260604.85: Global MASTER-Net observations report
  15. GRB 260604C: SVOM detection of a long burst
  16. GRB 260604C: Fermi GBM Final Real-time Localization
  17. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  18. GRB 260603A: NOT optical observations
  19. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  20. GRB 260604B: Fermi GBM Final Real-time Localization
  21. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  22. EP260602a: EP-FXT follow-up observation
  23. EP260603a: Global MASTER-Net observations report
  24. EP260603a: Einstein Probe detection of a fast X-ray transient
  25. EP260602d: Optical Upper limits with kinder observations
  26. GRB 260604A: Fermi GBM Final Real-time Localization
  27. EP260602b: Liverpool Telescope observations
  28. EP260602a: Liverpool Telescope optical upper limits
  29. EP260602b: Liverpool Telescope and LCO observations
  30. GRB 260603B: Fermi GBM Final Localization
  31. EP260602a: GTC and Liverpool Telescope optical observations
  32. Konus-Wind detection of GRB 260601B/EP260601a
  33. GRB 260603A: EP-FXT follow-up observation
  34. EP260601a/GRB 260601B: EP-FXT follow-up observation
  35. GRB 260601B / EP260601a: Mondy optical upper limit
  36. EP260602b: EP-FXT follow-up observation
  37. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  38. GRB 260603A: Kilonova-Catcher optical upper limit
  39. GRB 260603A: SVOM/VT optical observations
  40. EP260602a: NOT NIR J-band observations
  41. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  42. EP260602d: Einstein Probe detection of a fast X-ray transient
  43. Fermi trigger No 802141998: Global MASTER-Net observations report
  44. EP260602a: SVOM/VT optical magnitudes correction
  45. GRB 260601A: SVOM/GRM observation of a short burst
  46. EP260602c: Einstein Probe detection of a fast X-ray transient
  47. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  48. EP260602a: COLIBRÍ optical observations
  49. GRB260601B/EP260601a: NOT near-infrared observations
  50. SVOM GRB260603.23: Global MASTER-Net observations report
  51. GRB 260603A: SVOM detection of a burst
  52. EP260602b: Einstein Probe detection of a fast X-ray transient
  53. GRB 260601B/EP260601a: Insight-HXMT detection
  54. Fermi GRB 260602B: Global MASTER-Net observations report
  55. Fermi GRB 260602B: Global MASTER-Net observations report
  56. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  57. EP260602a: SVOM/VT optical candidate
  58. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  59. GRB 260602B: Fermi GBM Final Localization
  60. GRB 260601A: GECAM-B observation of a short burst
  61. GRB 260601B/EP260601a: J-band upper limit with WINTER
  62. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  63. EP260530a/AT 2026nwl: KAIT optical observations
  64. GRB 260602A: Fermi GBM Final Real-time Localization
  65. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  66. EP260602a: Optical upper limits with Kinder observations
  67. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  68. EP260602a: Einstein Probe detection of a fast X-ray transient
  69. GRB 260601B/EP260601a: SVOM/VT optical observations
  70. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  71. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  72. EP260601a: Einstein Probe detection of an X-ray transient
  73. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  74. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  75. GRB 260601A: Glowbug gamma-ray detection of a short burst
  76. GRB 260531B: Glowbug gamma-ray detection
  77. GRB 260516D: VLA radio detection
  78. GRB 260601A: Fermi GBM Observation
  79. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  80. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  81. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  82. Fermi GRB 260601A: Global MASTER-Net observations report
  83. GRB 260601A: Fermi GBM Final Real-time Localization
  84. GRB 260531B: GECAM-B observation
  85. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  86. The EP-WXT trigger 01709266272 is likely a flaring star
  87. GRB 260531C: Fermi GBM Final Localization Correction
  88. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  89. AT2026nik: EP-FXT X-ray counterpart
  90. Fermi trigger No 801900520: Global MASTER-Net observations report
  91. GRB 260531B: Fermi GBM Final Real-time Localization
  92. GRB 260531A: MAXI/GSC detection
  93. AT 2026nuz: COLIBRÍ optical observations
  94. IPN triangulation of GRB 260527A / EP260527a
  95. EP260527a/GRB 260527A: further FTW optical and NIR observations
  96. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  97. GRB 260530A: Fermi GBM Final Real-time Localization
  98. GRB 260527A / EP260527a: VLA radio detection
  99. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  100. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate

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