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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. EP260213a: Einstein Probe detection of a fast X-ray transient
  2. EP/WXT 01709258378: NOT optical upper limits
  3. GRB 260212A: SVOM/GRM observation of a long burst
  4. GRB 260213B: Fermi GBM Final Localization
  5. GRB 260213B: BALROG localization (Fermi Trigger 792697214 / GRB 260213736)
  6. GRB 260211A - SVOM/ECLAIRs refined analysis
  7. GRB 260204A: SVOM/ECLAIRs refined analysis
  8. GRB 260213A: Fermi GBM Final Localization
  9. GRB 260211A: EP-FXT follow-up observation
  10. GRB 260211A: SVOM/VT optical observation
  11. GRB 260212A: Glowbug gamma-ray detection
  12. GRB 260211A: GOTO optical upper limit
  13. Fermi GRB 260212A: Global MASTER-Net observations report
  14. GRB 260212A: Fermi GBM Final Real-time Localization
  15. GRB 260211A: LAST optical upper limit
  16. GRB 260210A: SVOM/GRM observation
  17. Fermi GBM Sub-Threshold Detection of GRB 260211A
  18. Konus-Wind detection of GRB 260207B
  19. GRB 260128B: SVOM/ECLAIRs refined analysis
  20. GRID detection of GRB 260207B
  21. GRB 260211A: LCO optical upper limits
  22. GRB260131A/B: 3.6m DOT Optical Observations
  23. GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  24. Fermi trigger No 792537871: Global MASTER-Net observations report
  25. GRB 260211A: SVOM detection of a burst
  26. Swift Operations Update + Community Forum (Friday, February 13 @ 10:00 AM EST)
  27. Konus-Wind detection of GRB 260209B
  28. GRB 260208A: Swift UVOT detection
  29. Konus-Wind detection of GRB 260127B
  30. EP260209a: COLIBRÍ optical upper limit
  31. Fermi GRB 260210C: Global MASTER-Net observations report
  32. EP260209a: LCO optical upper limits
  33. EP260210a: Global MASTER-Net observations report
  34. EP260210a: refined analysis of the EP-FXT observation
  35. EP260209a: Global MASTER-Net observations report
  36. GRB 260208A: LCO detection of the optical counterpart
  37. EP260209a: Einstein Probe detection of a fast X-ray transient
  38. EP260210a: Optical upper limits with Kinder observations
  39. IPN triangulation of GRB 260207B (short/hard with EE)
  40. GRB 260210C: Fermi GBM Final Real-time Localization
  41. GRB 260210A: Glowbug gamma-ray detection
  42. GRB 260210B: Fermi GBM Final Real-time Localization
  43. EP260210a: SVOM/VT optical upper limit
  44. GRB 260210A: AstroSat CZTI detection
  45. GRB 260208C: AstroSat CZTI detection
  46. EP260210a: COLIBRÍ optical upper limit
  47. EP260210a: SVOM/C-GFT upper limit
  48. GRB 260208B: refined analysis of the EP-FXT observation
  49. EP260210a: Einstein Probe detection of an X-ray transient
  50. GRB 260207B: AstroSat CZTI detection
  51. GRB 260208C: SVOM/GRM observation
  52. GRB 260204A: Swift-XRT afterglow detection
  53. GRB 260208B: AstroSat CZTI detection of a bright long burst
  54. GRB260208A: Liverpool Telescope optical follow-up observations
  55. GRB 260208A: Glowbug gamma-ray detection
  56. GRB 260208A: NuSTAR detection of prompt emission
  57. GRB 260208A: Fermi GBM Observation
  58. Fermi GRB 260209A: Global MASTER-Net observations report
  59. GRB 260208B: Swift-XRT observations
  60. GRB 260131A/B: continued Mondy optical observations
  61. GRB 260204A: Swift/UVOT Upper Limits
  62. GRB 260208B: COLIBRÍ optical observations
  63. GRB 260208A: Mondy optical observations (duplicate submission)
  64. GRB 260208A: Mondy optical observations
  65. GRB 260208A: 1.3m DFOT optical detection
  66. GRB 260208A: COLIBRÍ optical observations
  67. GRB 260208B: EP-FXT observation
  68. GRB 260208A: NOT spectroscopic redshift z = 2.36
  69. GRB 260208A: Liverpool Telescope optical detection
  70. Fermi GRB 260208C: Global MASTER-Net observations report
  71. GRB 260208B: SVOM/VT optical candidate
  72. GRB 260208A: GECAM-B observation of a bright burst
  73. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  74. GRB 260209A: Fermi GBM Final Real-time Localization
  75. GRB 260208A: SVOM/VT optical observation
  76. Fermi GRB 260208D: Global MASTER-Net observations report
  77. GRB 260208D: Fermi GBM Final Real-time Localization
  78. GRB 260208A: Swift-XRT observations
  79. GRB 260208B: Swift ToO observations
  80. GRB 260208B: SVOM/GRM observation of a bright burst
  81. GRB 260208B: Fermi GBM Detection
  82. LAT GRB 260208B: Global MASTER-Net observations report
  83. GRB 260208B: Fermi-LAT detection
  84. GRB 260208C: Fermi GBM Final Real-time Localization
  85. GRB 260208A: Fermi-LAT detection
  86. GRB 260207B: GECAM-B observation
  87. GRB 260208A: Swift ToO observations
  88. GRB 260208A: Fermi GBM Classification Correction
  89. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  90. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  91. GRB 260208B: BALROG localization (Fermi Trigger 792237169 / GRB 260208412)
  92. GRB 260208B: Fermi GBM Final Real-time Localization
  93. Fermi GRB 260208A: Global MASTER-Net observations report
  94. Fermi Gamma-ray Burst Monitor trigger 792220053/260208214 is not a GRB
  95. GRB 260208A: Fermi GBM Final Real-time Localization
  96. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  97. GRB 260207A : MASTER optical counterpart discovery
  98. GRB 260131A/B: Mondy and Terskol optical observations
  99. Fermi GRB 260207B: Global MASTER-Net observations report
  100. GRB 260206A: Swift-XRT observations

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