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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"

44350 results found.

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

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