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

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