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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. The EP-WXT trigger 01709266147 is likely a flaring star
  2. Fermi trigger No 801580882: Global MASTER-Net observations report
  3. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  4. EP260526a: LCO optical upper limits
  5. EP260526a: Einstein Probe detection of a fast X-ray transient
  6. GRB 260525A: AstroSat CZTI detection
  7. EP260526.405: COLIBRÍ optical upper limits
  8. The EP-WXT trigger 01709266106 is not a real source
  9. Fermi GRB 260526A: Global MASTER-Net observations report
  10. GRB 260526A: Fermi GBM Final Real-time Localization
  11. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  12. EP-WXT 01709266106: NOT optical upper limits
  13. Fermi GRB 260525A: Global MASTER-Net observations report
  14. GRB 260525A: Fermi GBM Final Real-time Localization
  15. GRB 260523B: AstroSat CZTI detection
  16. GRB 260523B: GECAM-B observation
  17. Fermi GRB 260523A: Global MASTER-Net observations report
  18. GRB 260523B: Fermi GBM Final Real-time Localization
  19. GRB 260523A: Fermi GBM Final Real-time Localization
  20. GRB 260522A: Fermi GBM Observation
  21. GRB 260522B: NuSTAR detection of prompt emission
  22. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  23. GRB 260522B: Fermi GBM Final Real-time Localization
  24. GRB 260522A: GOTO optical upper limit
  25. Fermi trigger No 801135305: Global MASTER-Net observations report
  26. Fermi GRB 260522A: Global MASTER-Net observations report
  27. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  28. GRB 260522A: Fermi-LAT detection
  29. GRB 260519C: SVOM/GRM observation
  30. GRB 260522A: Fermi GBM Final Real-time Localization
  31. GRB 260511A: iTelescope T-75 optical detection
  32. GRB 260520B: SVOM/GRM observation
  33. GRB 260411B: TERI Gamma-ray detection
  34. GRB 260407A: TERI Gamma-ray detection
  35. GRB 260307A: TERI Gamma-ray detection
  36. GRB 260225D: TERI Gamma-ray detection
  37. GRB 251118A: TERI Gamma-ray detection
  38. GRB 251113A: TERI Gamma-ray detection
  39. GRB 260428A: TERI Gamma-ray detection
  40. Konus-Wind detection of GRB 260519C
  41. GRB 260520B: Fermi GBM Final Localization
  42. GRB 260509A: SVOM/ECLAIRs refined analysis
  43. GRB 260520A: Fermi GBM Final Localization
  44. GRB 260519D: Fermi GBM Final Localization Correction
  45. GRB 260519C: NuSTAR detection of prompt emission
  46. Konus-Wind detection of GRB 260518A
  47. GRB 260519B: Fermi GBM Final Localization
  48. GRB 260519A: Fermi GBM Final Localization
  49. GRB 260518A: AstroSat CZTI detection of a long burst
  50. GRB 260516D: SVOM/ECLAIRs refined analysis
  51. GRB 260515A: SVOM/ECLAIRs refined analysis
  52. GRB 260421B: radio detection with the VLA
  53. GRID detection of GRB 260511A
  54. GRB 260509A: CrAO ZTSh optical upper limit (Duplicate Submission)
  55. GRB 260509A: CrAO ZTSh optical upper limit
  56. GRB 260516D: EP-FXT follow-up observation
  57. GRB 260516D: GOTO optical counterpart detection
  58. GRB 260516D: LCO optical observations
  59. GRB 260515A: further Liverpool Telescope observations
  60. GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
  61. GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801
  62. GRB 260516D: GROWTH-India Telescope optical detection
  63. GRB 260516D: SVOM/VT optical bright candidate
  64. GRB 260516D: FRAM-ORM optical limit
  65. GRB 260515A: CrAO ZTSh BVRI optical observations
  66. Fermi GRB 260516C: Global MASTER-Net observations report
  67. SVOM GRB260516D: Global MASTER-Net observations report
  68. GRB 260516D: SVOM possible detection of a burst
  69. GRB 260516C: Fermi GBM Final Real-time Localization
  70. Konus-Wind detection of GRB 260515A
  71. GRB 260515A: Liverpool Telescope optical detection
  72. GRB 260515A: LCO optical counterpart detection
  73. Fermi Gamma-ray Burst Monitor trigger 800627191/260516518 is not a GRB
  74. GRB 260515A: SVOM/COLIBRÍ (FM-GFT) optical observations
  75. GRB 260515A: EP-FXT follow-up observation
  76. EP260514a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  77. EP260514a: NOT optical counterpart confirmation
  78. EP260514a: TRT optical counterpart candidate
  79. EP260514a: SVOM/VT optical candidate
  80. Fermi GRB 260516B: Global MASTER-Net observations report
  81. GRB 260516B: Fermi GBM Final Real-time Localization
  82. Fermi Gamma-ray Burst Monitor trigger 800592653/260516119 is not a GRB
  83. GRB 260515A: SVOM/VT optical observations
  84. GRB 260515A: OHP/T193 optical observations
  85. EP260514a: COLIBRÍ optical upper limits
  86. GRB 260516A: Fermi GBM Final Real-time Localization
  87. GRID detection of GRB 260507A
  88. GRB 260515A: GTC/OSIRIS+ spectroscopic redshift z = 0.764
  89. GRB 260515A: LCO optical observations
  90. SVOM GRB 260515A: Global MASTER-Net observations report
  91. GRB 260515A: NOT optical observations.
  92. SVOM GRB 260515A: MASTER OT J151044.43+243321.7 optical counterpart detection
  93. GRB 260515A: SVOM/VT optical candidate from VHF data
  94. GRB 260515A: JinShan optical counterpart candidate
  95. GRB 260515A: SVOM detection of a burst
  96. GRB 260510C: Glowbug gamma-ray detection
  97. IceCube-260504A: No Candidate Transients from the Zwicky Transient Facility
  98. EP260514a: GROWTH-India Telescope optical upper limit
  99. GRB 260511B: NOT optical observations
  100. Konus-Wind detection of GRB 260512A

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