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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 260310A / AT 2026fgk: COLIBRÍ optical observations
  2. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  3. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  4. GRB260310A / AT2026fgk: P200 Spectroscopy
  5. GRB 260312B: Glowbug gamma-ray detection
  6. GRB 260310A: Fermi GBM Observation
  7. GRB 260310A: potential optical counterpart
  8. Fermi GRB 260312B: Global MASTER-Net observations report
  9. Fermi GRB 260311B: Global MASTER-Net observations report
  10. Swift BAT trigger 1500148: A solar flare
  11. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  12. GRB 260312B: Fermi GBM Final Real-time Localization
  13. The EP-WXT trigger 01709258843 is not a real source
  14. GRB 260310B: GECAM-B observation of a burst
  15. Retraction of GCN 43965: GRB is actually solar flare
  16. GRB 260312A: Swift detection of a burst
  17. GRB 260311B: Fermi GBM Final Real-time Localization
  18. GRB 260131A/B: radio detection with the VLA
  19. EP260302a: MeerKAT radio counterpart
  20. GRB260307A: GECAM-B observation of a burst
  21. GRB 260308A: SVOM/GRM observation of a short GRB
  22. EP260306a: Mondy optical upper limit
  23. GRB 260310A: AstroSat CZTI detection of a long burst
  24. GRB 260311A: Fermi GBM Final Real-time Localization
  25. Fermi GRB 260310B: Global MASTER-Net observations report
  26. GRB 260310B: Fermi GBM Final Real-time Localization
  27. Fermi GRB 260310A: Global MASTER-Net observations report
  28. GRB 260307B: SVOM/ECLAIRs refined analysis
  29. GRB 260208A: radio detection with the VLA
  30. GRB 260310A: Fermi GBM Final Real-time Localization
  31. GRB 260307A: Glowbug gamma-ray detection
  32. GRB 260308A: Fermi GBM Final Real-time Localization
  33. Fermi GBM Sub-Threshold Detection of GRB 260307B
  34. GRB 260307B: Mephisto optical upper limits
  35. GRB 260307B: possible NOT optical counterpart
  36. GRB 260307B: SVOM/VT upper limit with X band data analysis
  37. Fermi GRB 260307A: Global MASTER-Net observations report
  38. GRB260307B: GROWTH-India Telescope optical upper limit
  39. GRB 260307B: SVOM/VT optical candidate
  40. GRB 260307B: SVOM/C-GFT upper limit
  41. GRB 260307B: SVOM detection of a burst
  42. GRB 260307A: Fermi GBM Final Localization
  43. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  44. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  45. GRB 260207A: TESS Detection and Possible VLA Counterpart
  46. EP260302a: SVOM/VT optical observation
  47. EP260306a: Gemini-North redshift z = 4.773
  48. EP260306a: SVOM/VT optical observation
  49. EP260302a: Gemini-South redshift z = 1.535
  50. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  51. EP260306a: Einstein Probe detection of an X-ray transient
  52. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  53. EP260302a: Optical afterglow rebrightening
  54. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  55. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  56. GRB 260303A: 1.3m DFOT optical upper limit
  57. EP260214b: ATCA 6 GHz observations
  58. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  59. GRB 260303A: SVOM/ECLAIRs refined analysis
  60. Fermi GRB 260305A: Global MASTER-Net observations report
  61. GRB 260305A: Fermi GBM Final Real-time Localization
  62. GRB 260303B: AstroSat CZTI detection
  63. GRB 260304A: AstroSat CZTI detection of a long burst
  64. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  65. GRB 260303A: SVOM/VT optical observations
  66. GRB 260303A: J-band observations with WINTER
  67. GRB 260303B: NuSTAR detection of prompt emission
  68. EP260302a: Global MASTER-Net observations report
  69. Fermi GRB 260303B: Global MASTER-Net observations report
  70. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  71. GRB 260228A: SVOM/ECLAIRs refined analysis
  72. GRB 260225A: SVOM/ECLAIRs refined analysis
  73. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  74. GRB 260303B: Fermi GBM Final Real-time Localization
  75. EP260302a: analysis of the follow-up EP-FXT observation
  76. EP260227a: Gemini-South optical observations
  77. EP260302a: LCO observations
  78. EP260302a: BOOTES-7 optical counterpart detection at early times
  79. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  80. GRB 260303A: SVOM detection of a burst
  81. GRB 260228A: EP-FXT follow-up observation
  82. EP260302a: Einstein Probe detection of an X-ray transient
  83. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  84. GRB 251130B: TERI Gamma-ray detection
  85. GRB 260208A: TERI Gamma-ray detection
  86. GRB 260302A: Fermi GBM Final Real-time Localization
  87. EP260227a: Mondy optical observations
  88. GRB 260228A: CAHA 2.2m telescope optical upper limit
  89. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  90. EP260227a: Mephisto optical detection
  91. GRID detection of GRB 260225D
  92. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  93. EP260227a: further LCO observations
  94. EP260227a: SVOM/VT optical observation
  95. GRB 260228A: SVOM/VT optical upper limits
  96. GRB 260225D: SVOM/GRM observation
  97. EP260227A: 3.6m DOT optical afterglow detection
  98. GRB 260225B: SVOM/GRM observation
  99. GRB 260228A: SVOM detection of a burst
  100. EP260227a: FTW optical and NIR observations

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