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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. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  2. EP260316a: Xinglong optical upper limit
  3. GRB 260316A: Fermi GBM Final Real-time Localization
  4. EP260316a: optical upper limit with Kinder observations
  5. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  6. GRB 260314A: Glowbug gamma-ray detection
  7. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  8. IceCube-260315A: COLIBRÍ optical observations
  9. EP260314a: Xinglong optical upper limit
  10. EP260314a: optical upper limit with Kinder observations
  11. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  12. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  13. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  14. GRB 260310A / AT 2026fgk: iTelescope optical observations
  15. EP260314a: COLIBRÍ optical upper limit
  16. GRID detection of GRB 260312B
  17. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  18. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  19. EP260314a: BOOTES-6/DPR optical upper limits at early times
  20. EP260314a: Global MASTER-Net observations report
  21. EP260314a: SVOM/VT optical candidate
  22. Fermi trigger No 795185313: Global MASTER-Net observations report
  23. IceCube Alert 260315A: Global MASTER-Net observations report
  24. EP260314a: Einstein Probe detection of an X-ray transient
  25. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  26. GRB 260314A: GECAM-B observation of a burst
  27. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  28. GRB 260310A / AT2026fgk: SAO RAS optical observations
  29. GRB 260310A/AT2026fgk: radio detection at 15GHz
  30. GRB 260310A / AT2026fgk: TNG NIR detection
  31. GRB 260310A / AT2026fgk: OASDG optical observations
  32. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  33. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  34. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  35. Fermi GRB 260314A: Global MASTER-Net observations report
  36. Fermi GRB 260313A: Global MASTER-Net observations report
  37. GRB 260314A: Fermi GBM Final Real-time Localization
  38. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  39. GRB 260313A: A Correction to the Fermi GBM Final Localization
  40. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  41. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  42. GRB 260310B: Insight-HXMT/HE detection
  43. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  44. GRB 260310A: NOT optical polarimetry
  45. GRB 260312B: AstroSat CZTI detection
  46. Swift BAT trigger 1500295: A solar flare
  47. GRB 260313A: Fermi GBM Final Real-time Localization
  48. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  49. Swift BAT trigger 1500287: A solar flare
  50. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  51. GRB 260308A: Insight-HXMT/HE detection
  52. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  53. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  54. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  55. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  56. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  57. GRB260310A / AT2026fgk: P200 Spectroscopy
  58. GRB 260312B: Glowbug gamma-ray detection
  59. GRB 260310A: Fermi GBM Observation
  60. GRB 260310A: potential optical counterpart
  61. Fermi GRB 260312B: Global MASTER-Net observations report
  62. Fermi GRB 260311B: Global MASTER-Net observations report
  63. Swift BAT trigger 1500148: A solar flare
  64. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  65. GRB 260312B: Fermi GBM Final Real-time Localization
  66. The EP-WXT trigger 01709258843 is not a real source
  67. GRB 260310B: GECAM-B observation of a burst
  68. Retraction of GCN 43965: GRB is actually solar flare
  69. GRB 260312A: Swift detection of a burst
  70. GRB 260311B: Fermi GBM Final Real-time Localization
  71. GRB 260131A/B: radio detection with the VLA
  72. EP260302a: MeerKAT radio counterpart
  73. GRB260307A: GECAM-B observation of a burst
  74. GRB 260308A: SVOM/GRM observation of a short GRB
  75. EP260306a: Mondy optical upper limit
  76. GRB 260310A: AstroSat CZTI detection of a long burst
  77. GRB 260311A: Fermi GBM Final Real-time Localization
  78. Fermi GRB 260310B: Global MASTER-Net observations report
  79. GRB 260310B: Fermi GBM Final Real-time Localization
  80. Fermi GRB 260310A: Global MASTER-Net observations report
  81. GRB 260307B: SVOM/ECLAIRs refined analysis
  82. GRB 260208A: radio detection with the VLA
  83. GRB 260310A: Fermi GBM Final Real-time Localization
  84. GRB 260307A: Glowbug gamma-ray detection
  85. GRB 260308A: Fermi GBM Final Real-time Localization
  86. Fermi GBM Sub-Threshold Detection of GRB 260307B
  87. GRB 260307B: Mephisto optical upper limits
  88. GRB 260307B: possible NOT optical counterpart
  89. GRB 260307B: SVOM/VT upper limit with X band data analysis
  90. Fermi GRB 260307A: Global MASTER-Net observations report
  91. GRB260307B: GROWTH-India Telescope optical upper limit
  92. GRB 260307B: SVOM/VT optical candidate
  93. GRB 260307B: SVOM/C-GFT upper limit
  94. GRB 260307B: SVOM detection of a burst
  95. GRB 260307A: Fermi GBM Final Localization
  96. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  97. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  98. GRB 260207A: TESS Detection and Possible VLA Counterpart
  99. EP260302a: SVOM/VT optical observation
  100. EP260306a: Gemini-North redshift z = 4.773

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