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

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