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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"

35948 results found.

  1. GRB 260210A: AstroSat CZTI detection
  2. GRB 260208C: AstroSat CZTI detection
  3. GRB 260208B: refined analysis of the EP-FXT observation
  4. GRB 260207B: AstroSat CZTI detection
  5. GRB 260208C: SVOM/GRM observation
  6. GRB 260204A: Swift-XRT afterglow detection
  7. GRB 260208B: AstroSat CZTI detection of a bright long burst
  8. GRB 260208A: Glowbug gamma-ray detection
  9. GRB 260208A: NuSTAR detection of prompt emission
  10. GRB 260208A: Fermi GBM Observation
  11. Fermi GRB 260209A: Global MASTER-Net observations report
  12. GRB 260208B: Swift-XRT observations
  13. GRB 260131A/B: continued Mondy optical observations
  14. GRB 260204A: Swift/UVOT Upper Limits
  15. GRB 260208B: COLIBRÍ optical observations
  16. GRB 260208A: Mondy optical observations (duplicate submission)
  17. GRB 260208A: Mondy optical observations
  18. GRB 260208A: 1.3m DFOT optical detection
  19. GRB 260208A: COLIBRÍ optical observations
  20. GRB 260208B: EP-FXT observation
  21. GRB 260208A: NOT spectroscopic redshift z = 2.36
  22. GRB 260208A: Liverpool Telescope optical detection
  23. Fermi GRB 260208C: Global MASTER-Net observations report
  24. GRB 260208B: SVOM/VT optical candidate
  25. GRB 260208A: GECAM-B observation of a bright burst
  26. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  27. GRB 260209A: Fermi GBM Final Real-time Localization
  28. GRB 260208A: SVOM/VT optical observation
  29. Fermi GRB 260208D: Global MASTER-Net observations report
  30. GRB 260208D: Fermi GBM Final Real-time Localization
  31. GRB 260208A: Swift-XRT observations
  32. GRB 260208B: Swift ToO observations
  33. GRB 260208B: SVOM/GRM observation of a bright burst
  34. GRB 260208B: Fermi GBM Detection
  35. LAT GRB 260208B: Global MASTER-Net observations report
  36. GRB 260208B: Fermi-LAT detection
  37. GRB 260208C: Fermi GBM Final Real-time Localization
  38. GRB 260208A: Fermi-LAT detection
  39. GRB 260207B: GECAM-B observation
  40. GRB 260208A: Swift ToO observations
  41. GRB 260208A: Fermi GBM Classification Correction
  42. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  43. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  44. GRB 260208B: BALROG localization (Fermi Trigger 792237169 / GRB 260208412)
  45. GRB 260208B: Fermi GBM Final Real-time Localization
  46. Fermi GRB 260208A: Global MASTER-Net observations report
  47. Fermi Gamma-ray Burst Monitor trigger 792220053/260208214 is not a GRB
  48. GRB 260208A: Fermi GBM Final Real-time Localization
  49. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  50. GRB 260207A : MASTER optical counterpart discovery
  51. GRB 260131A/B: Mondy and Terskol optical observations
  52. Fermi GRB 260207B: Global MASTER-Net observations report
  53. GRB 260206A: Swift-XRT observations
  54. GRB 260207B: Fermi GBM Final Real-time Localization
  55. GRB 260207A: Fermi GBM Final Localization
  56. EP260131a: VLA detection
  57. GRB 260206A: Tiled Swift observations
  58. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  59. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  60. GRB 260204A: Swift-XRT observations
  61. GRB 260204A: LCO optical afterglow detection
  62. GRB 260204A: SVOM/VT optical candidate
  63. GRB 260204A : MASTER Global robotic net optical observations
  64. Fermi GBM Sub-Threshold Detection of GRB 260204A
  65. GRB 260204A: GOTO optical upper limit
  66. GRB 260204A: LCO optical upper limits
  67. GRB 260204B: Fermi GBM Final Real-time Localization
  68. GRB 260204A: SVOM detection of a burst
  69. GRB 260121A: 239Alferov CubeSat detection
  70. Konus-Wind detection of GRB 260121A
  71. GRB 260131A/B: OHP/T193 optical observations
  72. GRB 260131A: KAIT optical observations
  73. GRB 251230A: MeerLICHT afterglow detection
  74. GRB 260131A: FTW optical and NIR observations
  75. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  76. GRID detection of GRB 260131A/B
  77. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  78. GRB 260130A: Insight-HXMT/HE detection
  79. GRB 260130A: GECAM-B observation of a short burst
  80. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  81. GRB 260131A/B: EP/FXT X-ray afterglow detection
  82. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  83. GRB 260127B: Insight-HXMT/HE detection
  84. GRB 260127B: GECAM-B observation of a short burst
  85. GRB 260127A: GECAM-B observation
  86. GRB 260131A: NOT spectroscopic redshift z = 1.434
  87. Konus-Wind detection of GRB 260128A / EP260128a
  88. GRB 260131A: Insight-HXMT/HE detection
  89. Konus-Wind detection of GRB 260131A/B
  90. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  91. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  92. GRB 260131A/B: Fermi GBM Observation
  93. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  94. GRB 260131B: MAXI/GSC detection
  95. GRB 260131A: Fermi GBM Final Real-time Localization
  96. GRB 260127B: AstroSat CZTI detection
  97. GRB 260130A: Fermi GBM Detection
  98. GRB 260127B: Fermi GBM Detection
  99. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  100. Fermi GRB 260130A: Global MASTER-Net observations report

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