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

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