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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"

28232 results found.

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

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