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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. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  2. The EP-WXT trigger 01709266798 is likely a flaring star
  3. GRB 260604C: Jinshan optical observations
  4. GRB 260604C: Fermi GBM Observation
  5. EP260602d: J-band upper limit with WINTER
  6. EP260602b: J-band upper limit with WINTER
  7. GRB 260604C: LAST detection of optical counterpart candidate
  8. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  9. Fermi GRB 260604C: Global MASTER-Net observations report
  10. Fermi GRB 260604C: Global MASTER-Net observations report
  11. SVOM GRB260604.85: Global MASTER-Net observations report
  12. GRB 260604C: SVOM detection of a long burst
  13. GRB 260604C: Fermi GBM Final Real-time Localization
  14. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  15. GRB 260603A: NOT optical observations
  16. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  17. GRB 260604B: Fermi GBM Final Real-time Localization
  18. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  19. EP260602a: EP-FXT follow-up observation
  20. EP260603a: Global MASTER-Net observations report
  21. EP260603a: Einstein Probe detection of a fast X-ray transient
  22. EP260602d: Optical Upper limits with kinder observations
  23. GRB 260604A: Fermi GBM Final Real-time Localization
  24. EP260602b: Liverpool Telescope observations
  25. EP260602a: Liverpool Telescope optical upper limits
  26. EP260602b: Liverpool Telescope and LCO observations
  27. GRB 260603B: Fermi GBM Final Localization
  28. EP260602a: GTC and Liverpool Telescope optical observations
  29. Konus-Wind detection of GRB 260601B/EP260601a
  30. GRB 260603A: EP-FXT follow-up observation
  31. EP260601a/GRB 260601B: EP-FXT follow-up observation
  32. GRB 260601B / EP260601a: Mondy optical upper limit
  33. EP260602b: EP-FXT follow-up observation
  34. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  35. GRB 260603A: Kilonova-Catcher optical upper limit
  36. GRB 260603A: SVOM/VT optical observations
  37. EP260602a: NOT NIR J-band observations
  38. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  39. EP260602d: Einstein Probe detection of a fast X-ray transient
  40. Fermi trigger No 802141998: Global MASTER-Net observations report
  41. EP260602a: SVOM/VT optical magnitudes correction
  42. GRB 260601A: SVOM/GRM observation of a short burst
  43. EP260602c: Einstein Probe detection of a fast X-ray transient
  44. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  45. EP260602a: COLIBRÍ optical observations
  46. GRB260601B/EP260601a: NOT near-infrared observations
  47. SVOM GRB260603.23: Global MASTER-Net observations report
  48. GRB 260603A: SVOM detection of a burst
  49. EP260602b: Einstein Probe detection of a fast X-ray transient
  50. GRB 260601B/EP260601a: Insight-HXMT detection
  51. Fermi GRB 260602B: Global MASTER-Net observations report
  52. Fermi GRB 260602B: Global MASTER-Net observations report
  53. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  54. EP260602a: SVOM/VT optical candidate
  55. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  56. GRB 260602B: Fermi GBM Final Localization
  57. GRB 260601A: GECAM-B observation of a short burst
  58. GRB 260601B/EP260601a: J-band upper limit with WINTER
  59. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  60. EP260530a/AT 2026nwl: KAIT optical observations
  61. GRB 260602A: Fermi GBM Final Real-time Localization
  62. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  63. EP260602a: Optical upper limits with Kinder observations
  64. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  65. EP260602a: Einstein Probe detection of a fast X-ray transient
  66. GRB 260601B/EP260601a: SVOM/VT optical observations
  67. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  68. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  69. EP260601a: Einstein Probe detection of an X-ray transient
  70. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  71. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  72. GRB 260601A: Glowbug gamma-ray detection of a short burst
  73. GRB 260531B: Glowbug gamma-ray detection
  74. GRB 260516D: VLA radio detection
  75. GRB 260601A: Fermi GBM Observation
  76. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  77. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  78. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  79. Fermi GRB 260601A: Global MASTER-Net observations report
  80. GRB 260601A: Fermi GBM Final Real-time Localization
  81. GRB 260531B: GECAM-B observation
  82. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  83. The EP-WXT trigger 01709266272 is likely a flaring star
  84. GRB 260531C: Fermi GBM Final Localization Correction
  85. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  86. AT2026nik: EP-FXT X-ray counterpart
  87. Fermi trigger No 801900520: Global MASTER-Net observations report
  88. GRB 260531B: Fermi GBM Final Real-time Localization
  89. GRB 260531A: MAXI/GSC detection
  90. AT 2026nuz: COLIBRÍ optical observations
  91. IPN triangulation of GRB 260527A / EP260527a
  92. EP260527a/GRB 260527A: further FTW optical and NIR observations
  93. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  94. GRB 260530A: Fermi GBM Final Real-time Localization
  95. GRB 260527A / EP260527a: VLA radio detection
  96. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  97. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  98. GRB 260529A: GOTO tentative optical afterglow candidate
  99. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  100. GRB 260527A/EP260527a: Insight-HXMT detection

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