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

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