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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 260212A: Global MASTER-Net observations report
  2. GRB 260212A: Fermi GBM Final Real-time Localization
  3. GRB 260211A: LAST optical upper limit
  4. GRB 260210A: SVOM/GRM observation
  5. Fermi GBM Sub-Threshold Detection of GRB 260211A
  6. Konus-Wind detection of GRB 260207B
  7. GRB 260128B: SVOM/ECLAIRs refined analysis
  8. GRID detection of GRB 260207B
  9. GRB 260211A: LCO optical upper limits
  10. GRB260131A/B: 3.6m DOT Optical Observations
  11. GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  12. Fermi trigger No 792537871: Global MASTER-Net observations report
  13. GRB 260211A: SVOM detection of a burst
  14. Swift Operations Update + Community Forum (Friday, February 13 @ 10:00 AM EST)
  15. Konus-Wind detection of GRB 260209B
  16. GRB 260208A: Swift UVOT detection
  17. Konus-Wind detection of GRB 260127B
  18. EP260209a: COLIBRÍ optical upper limit
  19. Fermi GRB 260210C: Global MASTER-Net observations report
  20. EP260209a: LCO optical upper limits
  21. EP260210a: Global MASTER-Net observations report
  22. EP260210a: refined analysis of the EP-FXT observation
  23. EP260209a: Global MASTER-Net observations report
  24. GRB 260208A: LCO detection of the optical counterpart
  25. EP260209a: Einstein Probe detection of a fast X-ray transient
  26. EP260210a: Optical upper limits with Kinder observations
  27. IPN triangulation of GRB 260207B (short/hard with EE)
  28. GRB 260210C: Fermi GBM Final Real-time Localization
  29. GRB 260210A: Glowbug gamma-ray detection
  30. GRB 260210B: Fermi GBM Final Real-time Localization
  31. EP260210a: SVOM/VT optical upper limit
  32. GRB 260210A: AstroSat CZTI detection
  33. GRB 260208C: AstroSat CZTI detection
  34. EP260210a: COLIBRÍ optical upper limit
  35. EP260210a: SVOM/C-GFT upper limit
  36. GRB 260208B: refined analysis of the EP-FXT observation
  37. EP260210a: Einstein Probe detection of an X-ray transient
  38. GRB 260207B: AstroSat CZTI detection
  39. GRB 260208C: SVOM/GRM observation
  40. GRB 260204A: Swift-XRT afterglow detection
  41. GRB 260208B: AstroSat CZTI detection of a bright long burst
  42. GRB260208A: Liverpool Telescope optical follow-up observations
  43. GRB 260208A: Glowbug gamma-ray detection
  44. GRB 260208A: NuSTAR detection of prompt emission
  45. GRB 260208A: Fermi GBM Observation
  46. Fermi GRB 260209A: Global MASTER-Net observations report
  47. GRB 260208B: Swift-XRT observations
  48. GRB 260131A/B: continued Mondy optical observations
  49. GRB 260204A: Swift/UVOT Upper Limits
  50. GRB 260208B: COLIBRÍ optical observations
  51. GRB 260208A: Mondy optical observations (duplicate submission)
  52. GRB 260208A: Mondy optical observations
  53. GRB 260208A: 1.3m DFOT optical detection
  54. GRB 260208A: COLIBRÍ optical observations
  55. GRB 260208B: EP-FXT observation
  56. GRB 260208A: NOT spectroscopic redshift z = 2.36
  57. GRB 260208A: Liverpool Telescope optical detection
  58. Fermi GRB 260208C: Global MASTER-Net observations report
  59. GRB 260208B: SVOM/VT optical candidate
  60. GRB 260208A: GECAM-B observation of a bright burst
  61. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  62. GRB 260209A: Fermi GBM Final Real-time Localization
  63. GRB 260208A: SVOM/VT optical observation
  64. Fermi GRB 260208D: Global MASTER-Net observations report
  65. GRB 260208D: Fermi GBM Final Real-time Localization
  66. GRB 260208A: Swift-XRT observations
  67. GRB 260208B: Swift ToO observations
  68. GRB 260208B: SVOM/GRM observation of a bright burst
  69. GRB 260208B: Fermi GBM Detection
  70. LAT GRB 260208B: Global MASTER-Net observations report
  71. GRB 260208B: Fermi-LAT detection
  72. GRB 260208C: Fermi GBM Final Real-time Localization
  73. GRB 260208A: Fermi-LAT detection
  74. GRB 260207B: GECAM-B observation
  75. GRB 260208A: Swift ToO observations
  76. GRB 260208A: Fermi GBM Classification Correction
  77. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  78. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  79. GRB 260208B: BALROG localization (Fermi Trigger 792237169 / GRB 260208412)
  80. GRB 260208B: Fermi GBM Final Real-time Localization
  81. Fermi GRB 260208A: Global MASTER-Net observations report
  82. Fermi Gamma-ray Burst Monitor trigger 792220053/260208214 is not a GRB
  83. GRB 260208A: Fermi GBM Final Real-time Localization
  84. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  85. GRB 260207A : MASTER optical counterpart discovery
  86. GRB 260131A/B: Mondy and Terskol optical observations
  87. Fermi GRB 260207B: Global MASTER-Net observations report
  88. GRB 260206A: Swift-XRT observations
  89. GRB 260207B: Fermi GBM Final Real-time Localization
  90. GRB 260207A: Fermi GBM Final Localization
  91. Fermi trigger No 792135758: Global MASTER-Net observations report
  92. EP260131a: VLA detection
  93. GRB 260206A: Tiled Swift observations
  94. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  95. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  96. GRB 260204A: Swift-XRT observations
  97. GRB 260204A: LCO optical afterglow detection
  98. GRB 260204A: SVOM/VT optical candidate
  99. GRB 260204A : MASTER Global robotic net optical observations
  100. Fermi GBM Sub-Threshold Detection of GRB 260204A

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