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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

28233 results found.

  1. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  2. EP260329a: COLIBRÍ optical upper limit
  3. EP260329a: EP-FXT follow up observation
  4. EP260329a: NOT optical counterpart candidate
  5. EP260329b: Global MASTER-Net observations report
  6. Fermi trigger No 796485221: Global MASTER-Net observations report
  7. GRB 260327A: Insight-HXMT/HE detection
  8. EP260329b: Optical follow-up with Kinder observations
  9. EP 260329b: COLIBRÍ optical observations
  10. EP260329a: Optical upper limit with Kinder observations
  11. EP260329b: LCO optical observations of the counterpart
  12. GRB 260326A: Insight-HXMT/HE detection
  13. EP260329b: Einstein Probe detection of an X-ray transient
  14. EP260329a: Einstein Probe detection of an X-ray transient
  15. EP-WXT trigger 01709259209: TRT optical counterpart detection
  16. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  17. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  18. EP260327a: SVOM/VT optical upper limits
  19. EP260327a: WINTER J-band upper limit
  20. EP260327a: COLIBRÍ optical upper limits
  21. EP260327a: Gemini-North optical upper limits
  22. EP260324a: GROWTH-India Telescope optical observation
  23. EP260327a: Global MASTER-Net observations report
  24. EP260327a: Einstein Probe detection of an X-ray transient
  25. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  26. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  27. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  28. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  29. GRB 260326A: Fermi GBM Detection
  30. EP260321a: JinShan near-infrared observations
  31. EP260321a: Upper limits from a neutrino search with IceCube
  32. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  33. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  34. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  35. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  36. Fermi GRB 260323A: Global MASTER-Net observations report
  37. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  38. GRB 260320A: Glowbug gamma-ray detection
  39. EP260321a: COLIBRÍ further optical observations and brightening
  40. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  41. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  42. GRB 260321A: EP-FXT follow-up observation
  43. EP260321a: GOTO detection of blue variable source
  44. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  45. EP260321a: further Kinder optical observations
  46. GRB 260321A: SVOM/VT optical upper limits
  47. EP260321a: Las Cumbres upper limit
  48. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  49. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  50. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  51. EP260321a: SVOM/VT optical upper limit
  52. Fermi GBM Sub-Threshold Detection of GRB 260321A
  53. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  54. EP260321a: Global MASTER-Net observations report
  55. EP260321a: Einstein Probe detection of an X-ray transient
  56. GRB 260318A: Glowbug gamma-ray detection
  57. GRB 260310A / AT 2026fgk: KAIT optical observations
  58. GRB 260320A: NuSTAR detection of prompt emission
  59. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  60. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  61. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  62. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  63. GRB 260318A: SVOM/GRM observation
  64. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  65. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  66. Fermi GRB 260318A: Global MASTER-Net observations report
  67. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  68. GRB 260310A / AT 2026fgk: radio detection with the VLA
  69. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  70. GRB 260310A / AT2026fgk: LCO optical observations
  71. GRB 260316B: SVOM/GRM observation
  72. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  73. EP260316a: COLIBRÍ faint optical counterpart candidate
  74. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  75. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  76. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  77. EP260316a: Xinglong optical upper limit
  78. EP260316a: optical upper limit with Kinder observations
  79. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  80. GRB 260314A: Glowbug gamma-ray detection
  81. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  82. IceCube-260315A: COLIBRÍ optical observations
  83. EP260314a: Xinglong optical upper limit
  84. EP260314a: optical upper limit with Kinder observations
  85. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  86. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  87. GRB 260310A / AT 2026fgk: iTelescope optical observations
  88. EP260314a: COLIBRÍ optical upper limit
  89. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  90. EP260314a: Global MASTER-Net observations report
  91. EP260314a: SVOM/VT optical candidate
  92. Fermi trigger No 795185313: Global MASTER-Net observations report
  93. IceCube Alert 260315A: Global MASTER-Net observations report
  94. EP260314a: Einstein Probe detection of an X-ray transient
  95. GRB 260310A / AT2026fgk: SAO RAS optical observations
  96. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  97. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  98. Fermi GRB 260314A: Global MASTER-Net observations report
  99. Fermi GRB 260313A: Global MASTER-Net observations report
  100. GRB 260310A/AT 2026fgk: WINTER NIR Detections

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