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

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