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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 260531A: MAXI/GSC detection
  2. AT 2026nuz: COLIBRÍ optical observations
  3. IPN triangulation of GRB 260527A / EP260527a
  4. EP260527a/GRB 260527A: further FTW optical and NIR observations
  5. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  6. GRB 260530A: Fermi GBM Final Real-time Localization
  7. GRB 260527A / EP260527a: VLA radio detection
  8. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  9. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  10. GRB 260529A: GOTO tentative optical afterglow candidate
  11. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  12. GRB 260527A/EP260527a: Insight-HXMT detection
  13. Fermi GRB 260529A: Global MASTER-Net observations report
  14. GRB 260529A: Fermi GBM Final Real-time Localization
  15. EP260526a: SVOM/VT optical upper limits
  16. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  17. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  18. EP260527a / GRB 260527A: NOT optical observations
  19. GRB 260527A/EP260527a: FTW optical and NIR observations
  20. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  21. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  22. EP260527a/GRB 260527A: EP-FXT follow-up observation
  23. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  24. GRB 260526A: GECAM-B observation
  25. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  26. EP260526a: EP-FXT follow-up observation
  27. EP260527a: SVOM/VT optical observation
  28. EP260527a: COLIBRÍ optical detection
  29. EP260527a: Einstein Probe detection of a fast X-ray transient
  30. The EP-WXT trigger 01709266172 is likely a flaring star
  31. The EP-WXT trigger 01709266147 is likely a flaring star
  32. Fermi trigger No 801580882: Global MASTER-Net observations report
  33. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  34. EP260526a: LCO optical upper limits
  35. EP260526a: Einstein Probe detection of a fast X-ray transient
  36. GRB 260525A: AstroSat CZTI detection
  37. EP260526.405: COLIBRÍ optical upper limits
  38. The EP-WXT trigger 01709266106 is not a real source
  39. Fermi GRB 260526A: Global MASTER-Net observations report
  40. GRB 260526A: Fermi GBM Final Real-time Localization
  41. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  42. EP-WXT 01709266106: NOT optical upper limits
  43. Fermi GRB 260525A: Global MASTER-Net observations report
  44. GRB 260525A: Fermi GBM Final Real-time Localization
  45. GRB 260523B: AstroSat CZTI detection
  46. GRB 260523B: GECAM-B observation
  47. Fermi GRB 260523A: Global MASTER-Net observations report
  48. GRB 260523B: Fermi GBM Final Real-time Localization
  49. GRB 260523A: Fermi GBM Final Real-time Localization
  50. GRB 260522A: Fermi GBM Observation
  51. GRB 260522B: NuSTAR detection of prompt emission
  52. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  53. GRB 260522B: Fermi GBM Final Real-time Localization
  54. GRB 260522A: GOTO optical upper limit
  55. Fermi trigger No 801135305: Global MASTER-Net observations report
  56. Fermi GRB 260522A: Global MASTER-Net observations report
  57. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  58. GRB 260522A: Fermi-LAT detection
  59. GRB 260519C: SVOM/GRM observation
  60. GRB 260522A: Fermi GBM Final Real-time Localization
  61. GRB 260511A: iTelescope T-75 optical detection
  62. GRB 260520B: SVOM/GRM observation
  63. GRB 260411B: TERI Gamma-ray detection
  64. GRB 260407A: TERI Gamma-ray detection
  65. GRB 260307A: TERI Gamma-ray detection
  66. GRB 260225D: TERI Gamma-ray detection
  67. GRB 251118A: TERI Gamma-ray detection
  68. GRB 251113A: TERI Gamma-ray detection
  69. GRB 260428A: TERI Gamma-ray detection
  70. Konus-Wind detection of GRB 260519C
  71. GRB 260520B: Fermi GBM Final Localization
  72. GRB 260509A: SVOM/ECLAIRs refined analysis
  73. GRB 260520A: Fermi GBM Final Localization
  74. GRB 260519D: Fermi GBM Final Localization Correction
  75. GRB 260519C: NuSTAR detection of prompt emission
  76. Konus-Wind detection of GRB 260518A
  77. GRB 260519B: Fermi GBM Final Localization
  78. GRB 260519A: Fermi GBM Final Localization
  79. GRB 260518A: AstroSat CZTI detection of a long burst
  80. GRB 260516D: SVOM/ECLAIRs refined analysis
  81. GRB 260515A: SVOM/ECLAIRs refined analysis
  82. GRB 260421B: radio detection with the VLA
  83. GRID detection of GRB 260511A
  84. GRB 260509A: CrAO ZTSh optical upper limit (Duplicate Submission)
  85. GRB 260509A: CrAO ZTSh optical upper limit
  86. GRB 260516D: EP-FXT follow-up observation
  87. GRB 260516D: GOTO optical counterpart detection
  88. GRB 260516D: LCO optical observations
  89. GRB 260515A: further Liverpool Telescope observations
  90. GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
  91. GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801
  92. GRB 260516D: GROWTH-India Telescope optical detection
  93. GRB 260516D: SVOM/VT optical bright candidate
  94. GRB 260516D: FRAM-ORM optical limit
  95. GRB 260515A: CrAO ZTSh BVRI optical observations
  96. Fermi GRB 260516C: Global MASTER-Net observations report
  97. SVOM GRB260516D: Global MASTER-Net observations report
  98. GRB 260516D: SVOM possible detection of a burst
  99. GRB 260516C: Fermi GBM Final Real-time Localization
  100. Konus-Wind detection of GRB 260515A

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