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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 260527A/EP260527a: Glowbug gamma-ray detection
  2. Fermi GRB 260601A: Global MASTER-Net observations report
  3. GRB 260601A: Fermi GBM Final Real-time Localization
  4. GRB 260531B: GECAM-B observation
  5. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  6. The EP-WXT trigger 01709266272 is likely a flaring star
  7. GRB 260531C: Fermi GBM Final Localization Correction
  8. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  9. AT2026nik: EP-FXT X-ray counterpart
  10. Fermi trigger No 801900520: Global MASTER-Net observations report
  11. GRB 260531B: Fermi GBM Final Real-time Localization
  12. GRB 260531A: MAXI/GSC detection
  13. AT 2026nuz: COLIBRÍ optical observations
  14. IPN triangulation of GRB 260527A / EP260527a
  15. EP260527a/GRB 260527A: further FTW optical and NIR observations
  16. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  17. GRB 260530A: Fermi GBM Final Real-time Localization
  18. GRB 260527A / EP260527a: VLA radio detection
  19. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  20. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  21. GRB 260529A: GOTO tentative optical afterglow candidate
  22. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  23. GRB 260527A/EP260527a: Insight-HXMT detection
  24. Fermi GRB 260529A: Global MASTER-Net observations report
  25. GRB 260529A: Fermi GBM Final Real-time Localization
  26. EP260526a: SVOM/VT optical upper limits
  27. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  28. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  29. EP260527a / GRB 260527A: NOT optical observations
  30. GRB 260527A/EP260527a: FTW optical and NIR observations
  31. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  32. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  33. EP260527a/GRB 260527A: EP-FXT follow-up observation
  34. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  35. GRB 260526A: GECAM-B observation
  36. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  37. EP260526a: EP-FXT follow-up observation
  38. EP260527a: SVOM/VT optical observation
  39. EP260527a: COLIBRÍ optical detection
  40. EP260527a: Einstein Probe detection of a fast X-ray transient
  41. The EP-WXT trigger 01709266172 is likely a flaring star
  42. The EP-WXT trigger 01709266147 is likely a flaring star
  43. Fermi trigger No 801580882: Global MASTER-Net observations report
  44. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  45. EP260526a: LCO optical upper limits
  46. EP260526a: Einstein Probe detection of a fast X-ray transient
  47. GRB 260525A: AstroSat CZTI detection
  48. EP260526.405: COLIBRÍ optical upper limits
  49. The EP-WXT trigger 01709266106 is not a real source
  50. Fermi GRB 260526A: Global MASTER-Net observations report
  51. GRB 260526A: Fermi GBM Final Real-time Localization
  52. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  53. EP-WXT 01709266106: NOT optical upper limits
  54. Fermi GRB 260525A: Global MASTER-Net observations report
  55. GRB 260525A: Fermi GBM Final Real-time Localization
  56. GRB 260523B: AstroSat CZTI detection
  57. GRB 260523B: GECAM-B observation
  58. Fermi GRB 260523A: Global MASTER-Net observations report
  59. GRB 260523B: Fermi GBM Final Real-time Localization
  60. GRB 260523A: Fermi GBM Final Real-time Localization
  61. GRB 260522A: Fermi GBM Observation
  62. GRB 260522B: NuSTAR detection of prompt emission
  63. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  64. GRB 260522B: Fermi GBM Final Real-time Localization
  65. GRB 260522A: GOTO optical upper limit
  66. Fermi trigger No 801135305: Global MASTER-Net observations report
  67. Fermi GRB 260522A: Global MASTER-Net observations report
  68. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  69. GRB 260522A: Fermi-LAT detection
  70. GRB 260519C: SVOM/GRM observation
  71. GRB 260522A: Fermi GBM Final Real-time Localization
  72. GRB 260511A: iTelescope T-75 optical detection
  73. GRB 260520B: SVOM/GRM observation
  74. GRB 260411B: TERI Gamma-ray detection
  75. GRB 260407A: TERI Gamma-ray detection
  76. GRB 260307A: TERI Gamma-ray detection
  77. GRB 260225D: TERI Gamma-ray detection
  78. GRB 251118A: TERI Gamma-ray detection
  79. GRB 251113A: TERI Gamma-ray detection
  80. GRB 260428A: TERI Gamma-ray detection
  81. Konus-Wind detection of GRB 260519C
  82. GRB 260520B: Fermi GBM Final Localization
  83. GRB 260509A: SVOM/ECLAIRs refined analysis
  84. GRB 260520A: Fermi GBM Final Localization
  85. GRB 260519D: Fermi GBM Final Localization Correction
  86. GRB 260519C: NuSTAR detection of prompt emission
  87. Konus-Wind detection of GRB 260518A
  88. GRB 260519B: Fermi GBM Final Localization
  89. GRB 260519A: Fermi GBM Final Localization
  90. GRB 260518A: AstroSat CZTI detection of a long burst
  91. GRB 260516D: SVOM/ECLAIRs refined analysis
  92. GRB 260515A: SVOM/ECLAIRs refined analysis
  93. GRB 260421B: radio detection with the VLA
  94. GRID detection of GRB 260511A
  95. GRB 260509A: CrAO ZTSh optical upper limit (Duplicate Submission)
  96. GRB 260509A: CrAO ZTSh optical upper limit
  97. GRB 260516D: EP-FXT follow-up observation
  98. GRB 260516D: GOTO optical counterpart detection
  99. GRB 260516D: LCO optical observations
  100. GRB 260515A: further Liverpool Telescope observations

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