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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. EP260602a: SVOM/VT optical candidate
  2. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  3. GRB 260602B: Fermi GBM Final Localization
  4. GRB 260601A: GECAM-B observation of a short burst
  5. GRB 260601B/EP260601a: J-band upper limit with WINTER
  6. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  7. EP260530a/AT 2026nwl: KAIT optical observations
  8. GRB 260602A: Fermi GBM Final Real-time Localization
  9. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  10. EP260602a: Optical upper limits with Kinder observations
  11. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  12. EP260602a: Einstein Probe detection of a fast X-ray transient
  13. GRB 260601B/EP260601a: SVOM/VT optical observations
  14. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  15. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  16. EP260601a: Einstein Probe detection of an X-ray transient
  17. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  18. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  19. GRB 260601A: Glowbug gamma-ray detection of a short burst
  20. GRB 260531B: Glowbug gamma-ray detection
  21. GRB 260516D: VLA radio detection
  22. GRB 260601A: Fermi GBM Observation
  23. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  24. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  25. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  26. Fermi GRB 260601A: Global MASTER-Net observations report
  27. GRB 260601A: Fermi GBM Final Real-time Localization
  28. GRB 260531B: GECAM-B observation
  29. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  30. The EP-WXT trigger 01709266272 is likely a flaring star
  31. GRB 260531C: Fermi GBM Final Localization Correction
  32. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  33. AT2026nik: EP-FXT X-ray counterpart
  34. Fermi trigger No 801900520: Global MASTER-Net observations report
  35. GRB 260531B: Fermi GBM Final Real-time Localization
  36. GRB 260531A: MAXI/GSC detection
  37. AT 2026nuz: COLIBRÍ optical observations
  38. IPN triangulation of GRB 260527A / EP260527a
  39. EP260527a/GRB 260527A: further FTW optical and NIR observations
  40. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  41. GRB 260530A: Fermi GBM Final Real-time Localization
  42. GRB 260527A / EP260527a: VLA radio detection
  43. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  44. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  45. GRB 260529A: GOTO tentative optical afterglow candidate
  46. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  47. GRB 260527A/EP260527a: Insight-HXMT detection
  48. Fermi GRB 260529A: Global MASTER-Net observations report
  49. GRB 260529A: Fermi GBM Final Real-time Localization
  50. EP260526a: SVOM/VT optical upper limits
  51. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  52. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  53. EP260527a / GRB 260527A: NOT optical observations
  54. GRB 260527A/EP260527a: FTW optical and NIR observations
  55. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  56. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  57. EP260527a/GRB 260527A: EP-FXT follow-up observation
  58. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  59. GRB 260526A: GECAM-B observation
  60. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  61. EP260526a: EP-FXT follow-up observation
  62. EP260527a: SVOM/VT optical observation
  63. EP260527a: COLIBRÍ optical detection
  64. EP260527a: Einstein Probe detection of a fast X-ray transient
  65. The EP-WXT trigger 01709266172 is likely a flaring star
  66. The EP-WXT trigger 01709266147 is likely a flaring star
  67. Fermi trigger No 801580882: Global MASTER-Net observations report
  68. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  69. EP260526a: LCO optical upper limits
  70. EP260526a: Einstein Probe detection of a fast X-ray transient
  71. GRB 260525A: AstroSat CZTI detection
  72. EP260526.405: COLIBRÍ optical upper limits
  73. The EP-WXT trigger 01709266106 is not a real source
  74. Fermi GRB 260526A: Global MASTER-Net observations report
  75. GRB 260526A: Fermi GBM Final Real-time Localization
  76. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  77. EP-WXT 01709266106: NOT optical upper limits
  78. Fermi GRB 260525A: Global MASTER-Net observations report
  79. GRB 260525A: Fermi GBM Final Real-time Localization
  80. GRB 260523B: AstroSat CZTI detection
  81. GRB 260523B: GECAM-B observation
  82. Fermi GRB 260523A: Global MASTER-Net observations report
  83. GRB 260523B: Fermi GBM Final Real-time Localization
  84. GRB 260523A: Fermi GBM Final Real-time Localization
  85. GRB 260522A: Fermi GBM Observation
  86. GRB 260522B: NuSTAR detection of prompt emission
  87. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  88. GRB 260522B: Fermi GBM Final Real-time Localization
  89. GRB 260522A: GOTO optical upper limit
  90. Fermi trigger No 801135305: Global MASTER-Net observations report
  91. Fermi GRB 260522A: Global MASTER-Net observations report
  92. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  93. GRB 260522A: Fermi-LAT detection
  94. GRB 260519C: SVOM/GRM observation
  95. GRB 260522A: Fermi GBM Final Real-time Localization
  96. GRB 260511A: iTelescope T-75 optical detection
  97. GRB 260520B: SVOM/GRM observation
  98. GRB 260411B: TERI Gamma-ray detection
  99. GRB 260407A: TERI Gamma-ray detection
  100. GRB 260307A: TERI Gamma-ray detection

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