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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"

28038 results found.

  1. EP260329a: J-band upper limit with WINTER
  2. GRB 260330A: Glowbug gamma-ray detection
  3. Fermi GBM Sub-Threshold Detection of GRB 260330B
  4. GRB 260330B: LCO optical upper limits
  5. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  6. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  7. EP260329a: COLIBRÍ optical upper limit
  8. EP260329a: EP-FXT follow up observation
  9. EP260329a: NOT optical counterpart candidate
  10. EP260329b: Global MASTER-Net observations report
  11. Fermi trigger No 796485221: Global MASTER-Net observations report
  12. GRB 260327A: Insight-HXMT/HE detection
  13. EP260329b: Optical follow-up with Kinder observations
  14. EP 260329b: COLIBRÍ optical observations
  15. EP260329a: Optical upper limit with Kinder observations
  16. EP260329b: LCO optical observations of the counterpart
  17. GRB 260326A: Insight-HXMT/HE detection
  18. EP260329b: Einstein Probe detection of an X-ray transient
  19. EP260329a: Einstein Probe detection of an X-ray transient
  20. EP-WXT trigger 01709259209: TRT optical counterpart detection
  21. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  22. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  23. EP260327a: SVOM/VT optical upper limits
  24. EP260327a: WINTER J-band upper limit
  25. EP260327a: COLIBRÍ optical upper limits
  26. EP260327a: Gemini-North optical upper limits
  27. EP260324a: GROWTH-India Telescope optical observation
  28. EP260327a: Global MASTER-Net observations report
  29. EP260327a: Einstein Probe detection of an X-ray transient
  30. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  31. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  32. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  33. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  34. GRB 260326A: Fermi GBM Detection
  35. EP260321a: JinShan near-infrared observations
  36. EP260321a: Upper limits from a neutrino search with IceCube
  37. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  38. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  39. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  40. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  41. Fermi GRB 260323A: Global MASTER-Net observations report
  42. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  43. GRB 260320A: Glowbug gamma-ray detection
  44. EP260321a: COLIBRÍ further optical observations and brightening
  45. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  46. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  47. GRB 260321A: EP-FXT follow-up observation
  48. EP260321a: GOTO detection of blue variable source
  49. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  50. EP260321a: further Kinder optical observations
  51. GRB 260321A: SVOM/VT optical upper limits
  52. EP260321a: Las Cumbres upper limit
  53. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  54. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  55. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  56. EP260321a: SVOM/VT optical upper limit
  57. Fermi GBM Sub-Threshold Detection of GRB 260321A
  58. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  59. EP260321a: Global MASTER-Net observations report
  60. EP260321a: Einstein Probe detection of an X-ray transient
  61. GRB 260318A: Glowbug gamma-ray detection
  62. GRB 260310A / AT 2026fgk: KAIT optical observations
  63. GRB 260320A: NuSTAR detection of prompt emission
  64. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  65. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  66. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  67. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  68. GRB 260318A: SVOM/GRM observation
  69. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  70. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  71. Fermi GRB 260318A: Global MASTER-Net observations report
  72. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  73. GRB 260310A / AT 2026fgk: radio detection with the VLA
  74. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  75. GRB 260310A / AT2026fgk: LCO optical observations
  76. GRB 260316B: SVOM/GRM observation
  77. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  78. EP260316a: COLIBRÍ faint optical counterpart candidate
  79. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  80. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  81. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  82. EP260316a: Xinglong optical upper limit
  83. EP260316a: optical upper limit with Kinder observations
  84. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  85. GRB 260314A: Glowbug gamma-ray detection
  86. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  87. IceCube-260315A: COLIBRÍ optical observations
  88. EP260314a: Xinglong optical upper limit
  89. EP260314a: optical upper limit with Kinder observations
  90. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  91. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  92. GRB 260310A / AT 2026fgk: iTelescope optical observations
  93. EP260314a: COLIBRÍ optical upper limit
  94. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  95. EP260314a: Global MASTER-Net observations report
  96. EP260314a: SVOM/VT optical candidate
  97. Fermi trigger No 795185313: Global MASTER-Net observations report
  98. IceCube Alert 260315A: Global MASTER-Net observations report
  99. EP260314a: Einstein Probe detection of an X-ray transient
  100. GRB 260310A / AT2026fgk: SAO RAS optical observations

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