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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 260208B: AstroSat CZTI detection of a bright long burst
  2. GRB260208A: Liverpool Telescope optical follow-up observations
  3. GRB 260208A: Glowbug gamma-ray detection
  4. GRB 260208A: NuSTAR detection of prompt emission
  5. GRB 260208A: Fermi GBM Observation
  6. Fermi GRB 260209A: Global MASTER-Net observations report
  7. GRB 260208B: Swift-XRT observations
  8. GRB 260131A/B: continued Mondy optical observations
  9. GRB 260204A: Swift/UVOT Upper Limits
  10. GRB 260208B: COLIBRÍ optical observations
  11. GRB 260208A: Mondy optical observations (duplicate submission)
  12. GRB 260208A: Mondy optical observations
  13. GRB 260208A: 1.3m DFOT optical detection
  14. GRB 260208A: COLIBRÍ optical observations
  15. GRB 260208B: EP-FXT observation
  16. GRB 260208A: NOT spectroscopic redshift z = 2.36
  17. GRB 260208A: Liverpool Telescope optical detection
  18. Fermi GRB 260208C: Global MASTER-Net observations report
  19. GRB 260208B: SVOM/VT optical candidate
  20. GRB 260208A: GECAM-B observation of a bright burst
  21. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  22. GRB 260209A: Fermi GBM Final Real-time Localization
  23. GRB 260208A: SVOM/VT optical observation
  24. Fermi GRB 260208D: Global MASTER-Net observations report
  25. GRB 260208D: Fermi GBM Final Real-time Localization
  26. GRB 260208A: Swift-XRT observations
  27. GRB 260208B: Swift ToO observations
  28. GRB 260208B: SVOM/GRM observation of a bright burst
  29. GRB 260208B: Fermi GBM Detection
  30. LAT GRB 260208B: Global MASTER-Net observations report
  31. GRB 260208B: Fermi-LAT detection
  32. GRB 260208C: Fermi GBM Final Real-time Localization
  33. GRB 260208A: Fermi-LAT detection
  34. GRB 260207B: GECAM-B observation
  35. GRB 260208A: Swift ToO observations
  36. GRB 260208A: Fermi GBM Classification Correction
  37. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  38. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  39. GRB 260208B: BALROG localization (Fermi Trigger 792237169 / GRB 260208412)
  40. GRB 260208B: Fermi GBM Final Real-time Localization
  41. Fermi GRB 260208A: Global MASTER-Net observations report
  42. Fermi Gamma-ray Burst Monitor trigger 792220053/260208214 is not a GRB
  43. GRB 260208A: Fermi GBM Final Real-time Localization
  44. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  45. GRB 260207A : MASTER optical counterpart discovery
  46. GRB 260131A/B: Mondy and Terskol optical observations
  47. Fermi GRB 260207B: Global MASTER-Net observations report
  48. GRB 260206A: Swift-XRT observations
  49. GRB 260207B: Fermi GBM Final Real-time Localization
  50. GRB 260207A: Fermi GBM Final Localization
  51. Fermi trigger No 792135758: Global MASTER-Net observations report
  52. EP260131a: VLA detection
  53. GRB 260206A: Tiled Swift observations
  54. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  55. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  56. GRB 260204A: Swift-XRT observations
  57. GRB 260204A: LCO optical afterglow detection
  58. GRB 260204A: SVOM/VT optical candidate
  59. GRB 260204A : MASTER Global robotic net optical observations
  60. Fermi GBM Sub-Threshold Detection of GRB 260204A
  61. GRB 260204A: GOTO optical upper limit
  62. GRB 260204A: LCO optical upper limits
  63. EP260110a: Late GTC/EMIR near-infrared observations
  64. GRB 260204B: Fermi GBM Final Real-time Localization
  65. GRB 260204A: SVOM detection of a burst
  66. GRB 260121A: 239Alferov CubeSat detection
  67. Konus-Wind detection of GRB 260121A
  68. GRB 260131A/B: OHP/T193 optical observations
  69. GRB 260131A: KAIT optical observations
  70. GRB 251230A: MeerLICHT afterglow detection
  71. GRB 260131A: FTW optical and NIR observations
  72. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  73. GRID detection of GRB 260131A/B
  74. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  75. GRB 260130A: Insight-HXMT/HE detection
  76. GRB 260130A: GECAM-B observation of a short burst
  77. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  78. GRB 260131A/B: EP/FXT X-ray afterglow detection
  79. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  80. GRB 260127B: Insight-HXMT/HE detection
  81. GRB 260127B: GECAM-B observation of a short burst
  82. GRB 260127A: GECAM-B observation
  83. GRB 260131A: NOT spectroscopic redshift z = 1.434
  84. EP260131a: Liverpool Telescope optical upper limits
  85. EP260131a: COLIBRÍ further observations
  86. Konus-Wind detection of GRB 260128A / EP260128a
  87. GRB 260131A: Insight-HXMT/HE detection
  88. Konus-Wind detection of GRB 260131A/B
  89. EP260131a: SVOM/VT optical observation
  90. EP260131a: Xinglong optical upper limit
  91. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  92. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  93. GRB 260131A/B: Fermi GBM Observation
  94. EP260131a: COLIBRÍ observations of slow optical fading
  95. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  96. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  97. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  98. GRB 260131B: MAXI/GSC detection
  99. GRB 260131A: Fermi GBM Final Real-time Localization
  100. EP260131a: COLIBRÍ optical observations of the counterpart

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