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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. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  2. IceCube-260315A: COLIBRÍ optical observations
  3. EP260314a: Xinglong optical upper limit
  4. EP260314a: optical upper limit with Kinder observations
  5. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  6. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  7. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  8. GRB 260310A / AT 2026fgk: iTelescope optical observations
  9. EP260314a: COLIBRÍ optical upper limit
  10. GRID detection of GRB 260312B
  11. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  12. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  13. EP260314a: BOOTES-6/DPR optical upper limits at early times
  14. EP260314a: Global MASTER-Net observations report
  15. EP260314a: SVOM/VT optical candidate
  16. Fermi trigger No 795185313: Global MASTER-Net observations report
  17. IceCube Alert 260315A: Global MASTER-Net observations report
  18. EP260314a: Einstein Probe detection of an X-ray transient
  19. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  20. GRB 260314A: GECAM-B observation of a burst
  21. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  22. GRB 260310A / AT2026fgk: SAO RAS optical observations
  23. GRB 260310A/AT2026fgk: radio detection at 15GHz
  24. GRB 260310A / AT2026fgk: TNG NIR detection
  25. GRB 260310A / AT2026fgk: OASDG optical observations
  26. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  27. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  28. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  29. Fermi GRB 260314A: Global MASTER-Net observations report
  30. Fermi GRB 260313A: Global MASTER-Net observations report
  31. GRB 260314A: Fermi GBM Final Real-time Localization
  32. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  33. GRB 260313A: A Correction to the Fermi GBM Final Localization
  34. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  35. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  36. GRB 260310B: Insight-HXMT/HE detection
  37. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  38. GRB 260310A: NOT optical polarimetry
  39. GRB 260312B: AstroSat CZTI detection
  40. Swift BAT trigger 1500295: A solar flare
  41. GRB 260313A: Fermi GBM Final Real-time Localization
  42. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  43. Swift BAT trigger 1500287: A solar flare
  44. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  45. GRB 260308A: Insight-HXMT/HE detection
  46. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  47. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  48. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  49. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  50. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  51. GRB260310A / AT2026fgk: P200 Spectroscopy
  52. GRB 260312B: Glowbug gamma-ray detection
  53. GRB 260310A: Fermi GBM Observation
  54. GRB 260310A: potential optical counterpart
  55. Fermi GRB 260312B: Global MASTER-Net observations report
  56. Fermi GRB 260311B: Global MASTER-Net observations report
  57. Swift BAT trigger 1500148: A solar flare
  58. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  59. GRB 260312B: Fermi GBM Final Real-time Localization
  60. The EP-WXT trigger 01709258843 is not a real source
  61. GRB 260310B: GECAM-B observation of a burst
  62. Retraction of GCN 43965: GRB is actually solar flare
  63. GRB 260312A: Swift detection of a burst
  64. GRB 260311B: Fermi GBM Final Real-time Localization
  65. GRB 260131A/B: radio detection with the VLA
  66. EP260302a: MeerKAT radio counterpart
  67. GRB260307A: GECAM-B observation of a burst
  68. GRB 260308A: SVOM/GRM observation of a short GRB
  69. EP260306a: Mondy optical upper limit
  70. GRB 260310A: AstroSat CZTI detection of a long burst
  71. GRB 260311A: Fermi GBM Final Real-time Localization
  72. Fermi GRB 260310B: Global MASTER-Net observations report
  73. GRB 260310B: Fermi GBM Final Real-time Localization
  74. Fermi GRB 260310A: Global MASTER-Net observations report
  75. GRB 260307B: SVOM/ECLAIRs refined analysis
  76. GRB 260208A: radio detection with the VLA
  77. GRB 260310A: Fermi GBM Final Real-time Localization
  78. GRB 260307A: Glowbug gamma-ray detection
  79. GRB 260308A: Fermi GBM Final Real-time Localization
  80. Fermi GBM Sub-Threshold Detection of GRB 260307B
  81. GRB 260307B: Mephisto optical upper limits
  82. GRB 260307B: possible NOT optical counterpart
  83. GRB 260307B: SVOM/VT upper limit with X band data analysis
  84. Fermi GRB 260307A: Global MASTER-Net observations report
  85. GRB260307B: GROWTH-India Telescope optical upper limit
  86. GRB 260307B: SVOM/VT optical candidate
  87. GRB 260307B: SVOM/C-GFT upper limit
  88. GRB 260307B: SVOM detection of a burst
  89. GRB 260307A: Fermi GBM Final Localization
  90. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  91. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  92. GRB 260207A: TESS Detection and Possible VLA Counterpart
  93. EP260302a: SVOM/VT optical observation
  94. EP260306a: Gemini-North redshift z = 4.773
  95. EP260306a: SVOM/VT optical observation
  96. EP260302a: Gemini-South redshift z = 1.535
  97. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  98. EP260306a: Einstein Probe detection of an X-ray transient
  99. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  100. EP260302a: Optical afterglow rebrightening

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