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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"

26826 results found.

  1. GRB 260209A: Fermi GBM Final Real-time Localization
  2. GRB 260208A: SVOM/VT optical observation
  3. Fermi GRB 260208D: Global MASTER-Net observations report
  4. GRB 260208D: Fermi GBM Final Real-time Localization
  5. GRB 260208B: SVOM/GRM observation of a bright burst
  6. GRB 260208B: Fermi GBM Detection
  7. LAT GRB 260208B: Global MASTER-Net observations report
  8. GRB 260208B: Fermi-LAT detection
  9. GRB 260208C: Fermi GBM Final Real-time Localization
  10. GRB 260208A: Fermi-LAT detection
  11. GRB 260207B: GECAM-B observation
  12. GRB 260208A: Fermi GBM Classification Correction
  13. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  14. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  15. GRB 260208B: BALROG localization (Fermi Trigger 792237169 / GRB 260208412)
  16. GRB 260208B: Fermi GBM Final Real-time Localization
  17. Fermi GRB 260208A: Global MASTER-Net observations report
  18. Fermi Gamma-ray Burst Monitor trigger 792220053/260208214 is not a GRB
  19. GRB 260208A: Fermi GBM Final Real-time Localization
  20. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  21. GRB 260207A : MASTER optical counterpart discovery
  22. Fermi GRB 260207B: Global MASTER-Net observations report
  23. GRB 260207B: Fermi GBM Final Real-time Localization
  24. GRB 260207A: Fermi GBM Final Localization
  25. Fermi trigger No 792135758: Global MASTER-Net observations report
  26. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  27. GRB 260204A: Swift-XRT observations
  28. GRB 260204A: LCO optical afterglow detection
  29. GRB 260204A: SVOM/VT optical candidate
  30. GRB 260204A : MASTER Global robotic net optical observations
  31. Fermi GBM Sub-Threshold Detection of GRB 260204A
  32. GRB 260204A: GOTO optical upper limit
  33. GRB 260204A: LCO optical upper limits
  34. EP260110a: Late GTC/EMIR near-infrared observations
  35. GRB 260204B: Fermi GBM Final Real-time Localization
  36. GRB 260204A: SVOM detection of a burst
  37. GRB 251230A: MeerLICHT afterglow detection
  38. GRB 260131A: FTW optical and NIR observations
  39. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  40. GRID detection of GRB 260131A/B
  41. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  42. GRB 260130A: GECAM-B observation of a short burst
  43. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  44. GRB 260131A/B: EP/FXT X-ray afterglow detection
  45. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  46. GRB 260127B: GECAM-B observation of a short burst
  47. GRB 260127A: GECAM-B observation
  48. GRB 260131A: NOT spectroscopic redshift z = 1.434
  49. EP260131a: Liverpool Telescope optical upper limits
  50. EP260131a: COLIBRÍ further observations
  51. EP260131a: SVOM/VT optical observation
  52. EP260131a: Xinglong optical upper limit
  53. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  54. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  55. GRB 260131A/B: Fermi GBM Observation
  56. EP260131a: COLIBRÍ observations of slow optical fading
  57. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  58. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  59. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  60. GRB 260131A: Fermi GBM Final Real-time Localization
  61. EP260131a: COLIBRÍ optical observations of the counterpart
  62. EP260131a: Las Cumbres detection of an optical counterpart
  63. GRB 260130A: Fermi GBM Detection
  64. EP260131a: Einstein Probe detection of an X-ray transient
  65. GRB 260127B: Fermi GBM Detection
  66. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  67. Fermi GRB 260130A: Global MASTER-Net observations report
  68. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  69. GRB 260130A: Fermi GBM Final Real-time Localization
  70. Fermi GRB 260129A: Global MASTER-Net observations report
  71. GRB 260128B: LCO optical upper limits
  72. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  73. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  74. GRB 260127A: Swift-BAT refined analysis
  75. GRB 260129B: Fermi GBM Final Localization
  76. GRB 260128B: SVOM detection of a burst through offline search
  77. GRB 260129A: Fermi GBM Final Localization
  78. IPN triangulation of GRB 260127B (short)
  79. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  80. EP260128a: NOT optical counterpart candidate
  81. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  82. EP260128a: LCO optical upper limits
  83. EP260126a: SVOM/VT optical upperlimit
  84. EP260128a: Global MASTER-Net observations report
  85. EP260128a: Einstein Probe detection of an X-ray transient
  86. Fermi GRB 260127A: Global MASTER-Net observations report
  87. GRB 260127A: Fermi GBM Observation
  88. GRB 260127A: COLIBRÍ optical observations
  89. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  90. GRB 260127A: Swift-XRT refined Analysis
  91. GRB 260127B: GOTO candidate optical counterpart
  92. GRB 260127A: SVOM/C-GFT optical observations
  93. The EP-WXT trigger 01709253145 is likely a flaring star
  94. Fermi GRB 260127B: Global MASTER-Net observations report
  95. GRB 260127B: Fermi GBM Final Real-time Localization
  96. Swift GRB 260127A: Global MASTER-Net observations report
  97. GRB 260127A: LCO optical afterglow discovery
  98. GRB 260127A: Swift detection of a burst
  99. GRB 260127A: Fermi GBM Final Real-time Localization
  100. EP260126a: EP-FXT follow-up observation

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