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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"

28037 results found.

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

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