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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"

26207 results found.

  1. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  2. GRB 260207A : MASTER optical counterpart discovery
  3. Fermi GRB 260207B: Global MASTER-Net observations report
  4. GRB 260207B: Fermi GBM Final Real-time Localization
  5. GRB 260207A: Fermi GBM Final Localization
  6. Fermi trigger No 792135758: Global MASTER-Net observations report
  7. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  8. GRB 260204A: Swift-XRT observations
  9. GRB 260204A: LCO optical afterglow detection
  10. GRB 260204A: SVOM/VT optical candidate
  11. GRB 260204A : MASTER Global robotic net optical observations
  12. Fermi GBM Sub-Threshold Detection of GRB 260204A
  13. GRB 260204A: GOTO optical upper limit
  14. GRB 260204A: LCO optical upper limits
  15. EP260110a: Late GTC/EMIR near-infrared observations
  16. GRB 260204B: Fermi GBM Final Real-time Localization
  17. GRB 260204A: SVOM detection of a burst
  18. GRB 251230A: MeerLICHT afterglow detection
  19. GRB 260131A: FTW optical and NIR observations
  20. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  21. GRID detection of GRB 260131A/B
  22. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  23. GRB 260130A: GECAM-B observation of a short burst
  24. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  25. GRB 260131A/B: EP/FXT X-ray afterglow detection
  26. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  27. GRB 260127B: GECAM-B observation of a short burst
  28. GRB 260127A: GECAM-B observation
  29. GRB 260131A: NOT spectroscopic redshift z = 1.434
  30. EP260131a: Liverpool Telescope optical upper limits
  31. EP260131a: COLIBRÍ further observations
  32. EP260131a: SVOM/VT optical observation
  33. EP260131a: Xinglong optical upper limit
  34. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  35. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  36. GRB 260131A/B: Fermi GBM Observation
  37. EP260131a: COLIBRÍ observations of slow optical fading
  38. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  39. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  40. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  41. GRB 260131A: Fermi GBM Final Real-time Localization
  42. EP260131a: COLIBRÍ optical observations of the counterpart
  43. EP260131a: Las Cumbres detection of an optical counterpart
  44. GRB 260130A: Fermi GBM Detection
  45. EP260131a: Einstein Probe detection of an X-ray transient
  46. GRB 260127B: Fermi GBM Detection
  47. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  48. Fermi GRB 260130A: Global MASTER-Net observations report
  49. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  50. GRB 260130A: Fermi GBM Final Real-time Localization
  51. Fermi GRB 260129A: Global MASTER-Net observations report
  52. GRB 260128B: LCO optical upper limits
  53. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  54. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  55. GRB 260127A: Swift-BAT refined analysis
  56. GRB 260129B: Fermi GBM Final Localization
  57. GRB 260128B: SVOM detection of a burst through offline search
  58. GRB 260129A: Fermi GBM Final Localization
  59. IPN triangulation of GRB 260127B (short)
  60. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  61. EP260128a: NOT optical counterpart candidate
  62. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  63. EP260128a: LCO optical upper limits
  64. EP260126a: SVOM/VT optical upperlimit
  65. EP260128a: Global MASTER-Net observations report
  66. EP260128a: Einstein Probe detection of an X-ray transient
  67. Fermi GRB 260127A: Global MASTER-Net observations report
  68. GRB 260127A: Fermi GBM Observation
  69. GRB 260127A: COLIBRÍ optical observations
  70. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  71. GRB 260127A: Swift-XRT refined Analysis
  72. GRB 260127B: GOTO candidate optical counterpart
  73. GRB 260127A: SVOM/C-GFT optical observations
  74. The EP-WXT trigger 01709253145 is likely a flaring star
  75. Fermi GRB 260127B: Global MASTER-Net observations report
  76. GRB 260127B: Fermi GBM Final Real-time Localization
  77. Swift GRB 260127A: Global MASTER-Net observations report
  78. GRB 260127A: LCO optical afterglow discovery
  79. GRB 260127A: Swift detection of a burst
  80. GRB 260127A: Fermi GBM Final Real-time Localization
  81. EP260126a: EP-FXT follow-up observation
  82. EP260126a: Optical upper limit with Kinder observations
  83. EP260126a: Further NOT optical upper limits
  84. EP260126a: COLIBRÍ optical upper limits
  85. EP260126a: NOT optical observations
  86. EP260126a: Einstein Probe detection of a fast X-ray transient
  87. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  88. Konus-Wind detection of GRB 260120B
  89. GRB 251222A: SVOM/ECLAIRs refined analysis
  90. GRB 260125A: GOTO candidate optical counterpart
  91. Fermi GRB 260125B: Global MASTER-Net observations report
  92. GRB 260125B: Fermi GBM Final Real-time Localization
  93. GRB 260125A: Fermi GBM Final Real-time Localization
  94. GRB 260114A: SVOM/VT optical upper limits
  95. GRB 260122B: Swift-BAT refined analysis
  96. GRB 260120B: SVOM/GRM observation
  97. GRB 260120A: GECAM-B observation
  98. GRB 260122B: Swift detection of a burst
  99. Swift GRB260122.97: Global MASTER-Net observations report
  100. GRB 260122A: Fermi GBM Final Real-time Localization

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