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

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