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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. AT 2026nuz: COLIBRÍ optical observations
  2. IPN triangulation of GRB 260527A / EP260527a
  3. EP260527a/GRB 260527A: further FTW optical and NIR observations
  4. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  5. GRB 260530A: Fermi GBM Final Real-time Localization
  6. GRB 260527A / EP260527a: VLA radio detection
  7. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  8. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  9. GRB 260529A: GOTO tentative optical afterglow candidate
  10. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  11. GRB 260527A/EP260527a: Insight-HXMT detection
  12. Fermi GRB 260529A: Global MASTER-Net observations report
  13. GRB 260529A: Fermi GBM Final Real-time Localization
  14. EP250526a: SVOM/VT optical upper limits
  15. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  16. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  17. EP260527a / GRB 260527A: NOT optical observations
  18. GRB 260527A/EP260527a: FTW optical and NIR observations
  19. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  20. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  21. EP260527a/GRB 260527A: EP-FXT follow-up observation
  22. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  23. GRB 260526A: GECAM-B observation
  24. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  25. EP260526a: EP-FXT follow-up observation
  26. EP260527a: SVOM/VT optical observation
  27. EP260527a: COLIBRÍ optical detection
  28. EP260527a: Einstein Probe detection of a fast X-ray transient
  29. The EP-WXT trigger 01709266172 is likely a flaring star
  30. The EP-WXT trigger 01709266147 is likely a flaring star
  31. Fermi trigger No 801580882: Global MASTER-Net observations report
  32. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  33. EP260526a: LCO optical upper limits
  34. EP260526a: Einstein Probe detection of a fast X-ray transient
  35. GRB 260525A: AstroSat CZTI detection
  36. EP260526.405: COLIBRÍ optical upper limits
  37. The EP-WXT trigger 01709266106 is not a real source
  38. Fermi GRB 260526A: Global MASTER-Net observations report
  39. GRB 260526A: Fermi GBM Final Real-time Localization
  40. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  41. EP-WXT 01709266106: NOT optical upper limits
  42. Fermi GRB 260525A: Global MASTER-Net observations report
  43. GRB 260525A: Fermi GBM Final Real-time Localization
  44. GRB 260523B: AstroSat CZTI detection
  45. GRB 260523B: GECAM-B observation
  46. Fermi GRB 260523A: Global MASTER-Net observations report
  47. GRB 260523B: Fermi GBM Final Real-time Localization
  48. GRB 260523A: Fermi GBM Final Real-time Localization
  49. GRB 260522A: Fermi GBM Observation
  50. GRB 260522B: NuSTAR detection of prompt emission
  51. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  52. GRB 260522B: Fermi GBM Final Real-time Localization
  53. GRB 260522A: GOTO optical upper limit
  54. Fermi trigger No 801135305: Global MASTER-Net observations report
  55. Fermi GRB 260522A: Global MASTER-Net observations report
  56. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  57. GRB 260522A: Fermi-LAT detection
  58. GRB 260519C: SVOM/GRM observation
  59. GRB 260522A: Fermi GBM Final Real-time Localization
  60. GRB 260511A: iTelescope T-75 optical detection
  61. GRB 260520B: SVOM/GRM observation
  62. GRB 260411B: TERI Gamma-ray detection
  63. GRB 260407A: TERI Gamma-ray detection
  64. GRB 260307A: TERI Gamma-ray detection
  65. GRB 260225D: TERI Gamma-ray detection
  66. GRB 251118A: TERI Gamma-ray detection
  67. GRB 251113A: TERI Gamma-ray detection
  68. GRB 260428A: TERI Gamma-ray detection
  69. Konus-Wind detection of GRB 260519C
  70. GRB 260520B: Fermi GBM Final Localization
  71. GRB 260509A: SVOM/ECLAIRs refined analysis
  72. GRB 260520A: Fermi GBM Final Localization
  73. GRB 260519D: Fermi GBM Final Localization Correction
  74. GRB 260519C: NuSTAR detection of prompt emission
  75. Konus-Wind detection of GRB 260518A
  76. GRB 260519B: Fermi GBM Final Localization
  77. GRB 260519A: Fermi GBM Final Localization
  78. GRB 260518A: AstroSat CZTI detection of a long burst
  79. GRB 260516D: SVOM/ECLAIRs refined analysis
  80. GRB 260515A: SVOM/ECLAIRs refined analysis
  81. GRB 260421B: radio detection with the VLA
  82. GRID detection of GRB 260511A
  83. GRB 260509A: CrAO ZTSh optical upper limit (Duplicate Submission)
  84. GRB 260509A: CrAO ZTSh optical upper limit
  85. GRB 260516D: EP-FXT follow-up observation
  86. GRB 260516D: GOTO optical counterpart detection
  87. GRB 260516D: LCO optical observations
  88. GRB 260515A: further Liverpool Telescope observations
  89. GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
  90. GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801
  91. GRB 260516D: GROWTH-India Telescope optical detection
  92. GRB 260516D: SVOM/VT optical bright candidate
  93. GRB 260516D: FRAM-ORM optical limit
  94. GRB 260515A: CrAO ZTSh BVRI optical observations
  95. Fermi GRB 260516C: Global MASTER-Net observations report
  96. SVOM GRB260516D: Global MASTER-Net observations report
  97. GRB 260516D: SVOM possible detection of a burst
  98. GRB 260516C: Fermi GBM Final Real-time Localization
  99. Konus-Wind detection of GRB 260515A
  100. GRB 260515A: Liverpool Telescope optical detection

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