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

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