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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. Fermi GRB 260529A: Global MASTER-Net observations report
  2. GRB 260529A: Fermi GBM Final Real-time Localization
  3. EP260526a: SVOM/VT optical upper limits
  4. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  5. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  6. EP260527a / GRB 260527A: NOT optical observations
  7. GRB 260527A/EP260527a: FTW optical and NIR observations
  8. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  9. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  10. EP260527a/GRB 260527A: EP-FXT follow-up observation
  11. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  12. GRB 260526A: GECAM-B observation
  13. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  14. EP260526a: EP-FXT follow-up observation
  15. EP260527a: SVOM/VT optical observation
  16. EP260527a: COLIBRÍ optical detection
  17. EP260527a: Einstein Probe detection of a fast X-ray transient
  18. The EP-WXT trigger 01709266172 is likely a flaring star
  19. The EP-WXT trigger 01709266147 is likely a flaring star
  20. Fermi trigger No 801580882: Global MASTER-Net observations report
  21. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  22. EP260526a: LCO optical upper limits
  23. EP260526a: Einstein Probe detection of a fast X-ray transient
  24. GRB 260525A: AstroSat CZTI detection
  25. EP260526.405: COLIBRÍ optical upper limits
  26. The EP-WXT trigger 01709266106 is not a real source
  27. Fermi GRB 260526A: Global MASTER-Net observations report
  28. GRB 260526A: Fermi GBM Final Real-time Localization
  29. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  30. EP-WXT 01709266106: NOT optical upper limits
  31. Fermi GRB 260525A: Global MASTER-Net observations report
  32. GRB 260525A: Fermi GBM Final Real-time Localization
  33. GRB 260523B: AstroSat CZTI detection
  34. GRB 260523B: GECAM-B observation
  35. Fermi GRB 260523A: Global MASTER-Net observations report
  36. GRB 260523B: Fermi GBM Final Real-time Localization
  37. GRB 260523A: Fermi GBM Final Real-time Localization
  38. GRB 260522A: Fermi GBM Observation
  39. GRB 260522B: NuSTAR detection of prompt emission
  40. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  41. GRB 260522B: Fermi GBM Final Real-time Localization
  42. GRB 260522A: GOTO optical upper limit
  43. Fermi trigger No 801135305: Global MASTER-Net observations report
  44. Fermi GRB 260522A: Global MASTER-Net observations report
  45. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  46. GRB 260522A: Fermi-LAT detection
  47. GRB 260519C: SVOM/GRM observation
  48. GRB 260522A: Fermi GBM Final Real-time Localization
  49. GRB 260511A: iTelescope T-75 optical detection
  50. GRB 260520B: SVOM/GRM observation
  51. GRB 260411B: TERI Gamma-ray detection
  52. GRB 260407A: TERI Gamma-ray detection
  53. GRB 260307A: TERI Gamma-ray detection
  54. GRB 260225D: TERI Gamma-ray detection
  55. GRB 251118A: TERI Gamma-ray detection
  56. GRB 251113A: TERI Gamma-ray detection
  57. GRB 260428A: TERI Gamma-ray detection
  58. Konus-Wind detection of GRB 260519C
  59. GRB 260520B: Fermi GBM Final Localization
  60. GRB 260509A: SVOM/ECLAIRs refined analysis
  61. GRB 260520A: Fermi GBM Final Localization
  62. GRB 260519D: Fermi GBM Final Localization Correction
  63. GRB 260519C: NuSTAR detection of prompt emission
  64. Konus-Wind detection of GRB 260518A
  65. GRB 260519B: Fermi GBM Final Localization
  66. GRB 260519A: Fermi GBM Final Localization
  67. GRB 260518A: AstroSat CZTI detection of a long burst
  68. GRB 260516D: SVOM/ECLAIRs refined analysis
  69. GRB 260515A: SVOM/ECLAIRs refined analysis
  70. GRB 260421B: radio detection with the VLA
  71. GRID detection of GRB 260511A
  72. GRB 260509A: CrAO ZTSh optical upper limit (Duplicate Submission)
  73. GRB 260509A: CrAO ZTSh optical upper limit
  74. GRB 260516D: EP-FXT follow-up observation
  75. GRB 260516D: GOTO optical counterpart detection
  76. GRB 260516D: LCO optical observations
  77. GRB 260515A: further Liverpool Telescope observations
  78. GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
  79. GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801
  80. GRB 260516D: GROWTH-India Telescope optical detection
  81. GRB 260516D: SVOM/VT optical bright candidate
  82. GRB 260516D: FRAM-ORM optical limit
  83. GRB 260515A: CrAO ZTSh BVRI optical observations
  84. Fermi GRB 260516C: Global MASTER-Net observations report
  85. SVOM GRB260516D: Global MASTER-Net observations report
  86. GRB 260516D: SVOM possible detection of a burst
  87. GRB 260516C: Fermi GBM Final Real-time Localization
  88. Konus-Wind detection of GRB 260515A
  89. GRB 260515A: Liverpool Telescope optical detection
  90. GRB 260515A: LCO optical counterpart detection
  91. Fermi Gamma-ray Burst Monitor trigger 800627191/260516518 is not a GRB
  92. GRB 260515A: SVOM/COLIBRÍ (FM-GFT) optical observations
  93. GRB 260515A: EP-FXT follow-up observation
  94. EP260514a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  95. EP260514a: NOT optical counterpart confirmation
  96. EP260514a: TRT optical counterpart candidate
  97. EP260514a: SVOM/VT optical candidate
  98. Fermi GRB 260516B: Global MASTER-Net observations report
  99. GRB 260516B: Fermi GBM Final Real-time Localization
  100. Fermi Gamma-ray Burst Monitor trigger 800592653/260516119 is not a GRB

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