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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"

28231 results found.

  1. EP260329a: NOT optical counterpart candidate
  2. EP260329b: Global MASTER-Net observations report
  3. Fermi trigger No 796485221: Global MASTER-Net observations report
  4. GRB 260327A: Insight-HXMT/HE detection
  5. EP260329b: Optical follow-up with Kinder observations
  6. EP 260329b: COLIBRÍ optical observations
  7. EP260329a: Optical upper limit with Kinder observations
  8. EP260329b: LCO optical observations of the counterpart
  9. GRB 260326A: Insight-HXMT/HE detection
  10. EP260329b: Einstein Probe detection of an X-ray transient
  11. EP260329a: Einstein Probe detection of an X-ray transient
  12. EP-WXT trigger 01709259209: TRT optical counterpart detection
  13. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  14. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  15. EP260327a: SVOM/VT optical upper limits
  16. EP260327a: WINTER J-band upper limit
  17. EP260327a: COLIBRÍ optical upper limits
  18. EP260327a: Gemini-North optical upper limits
  19. EP260324a: GROWTH-India Telescope optical observation
  20. EP260327a: Global MASTER-Net observations report
  21. EP260327a: Einstein Probe detection of an X-ray transient
  22. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  23. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  24. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  25. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  26. GRB 260326A: Fermi GBM Detection
  27. EP260321a: JinShan near-infrared observations
  28. EP260321a: Upper limits from a neutrino search with IceCube
  29. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  30. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  31. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  32. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  33. Fermi GRB 260323A: Global MASTER-Net observations report
  34. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  35. GRB 260320A: Glowbug gamma-ray detection
  36. EP260321a: COLIBRÍ further optical observations and brightening
  37. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  38. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  39. GRB 260321A: EP-FXT follow-up observation
  40. EP260321a: GOTO detection of blue variable source
  41. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  42. EP260321a: further Kinder optical observations
  43. GRB 260321A: SVOM/VT optical upper limits
  44. EP260321a: Las Cumbres upper limit
  45. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  46. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  47. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  48. EP260321a: SVOM/VT optical upper limit
  49. Fermi GBM Sub-Threshold Detection of GRB 260321A
  50. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  51. EP260321a: Global MASTER-Net observations report
  52. EP260321a: Einstein Probe detection of an X-ray transient
  53. GRB 260318A: Glowbug gamma-ray detection
  54. GRB 260310A / AT 2026fgk: KAIT optical observations
  55. GRB 260320A: NuSTAR detection of prompt emission
  56. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  57. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  58. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  59. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  60. GRB 260318A: SVOM/GRM observation
  61. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  62. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  63. Fermi GRB 260318A: Global MASTER-Net observations report
  64. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  65. GRB 260310A / AT 2026fgk: radio detection with the VLA
  66. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  67. GRB 260310A / AT2026fgk: LCO optical observations
  68. GRB 260316B: SVOM/GRM observation
  69. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  70. EP260316a: COLIBRÍ faint optical counterpart candidate
  71. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  72. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  73. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  74. EP260316a: Xinglong optical upper limit
  75. EP260316a: optical upper limit with Kinder observations
  76. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  77. GRB 260314A: Glowbug gamma-ray detection
  78. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  79. IceCube-260315A: COLIBRÍ optical observations
  80. EP260314a: Xinglong optical upper limit
  81. EP260314a: optical upper limit with Kinder observations
  82. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  83. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  84. GRB 260310A / AT 2026fgk: iTelescope optical observations
  85. EP260314a: COLIBRÍ optical upper limit
  86. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  87. EP260314a: Global MASTER-Net observations report
  88. EP260314a: SVOM/VT optical candidate
  89. Fermi trigger No 795185313: Global MASTER-Net observations report
  90. IceCube Alert 260315A: Global MASTER-Net observations report
  91. EP260314a: Einstein Probe detection of an X-ray transient
  92. GRB 260310A / AT2026fgk: SAO RAS optical observations
  93. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  94. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  95. Fermi GRB 260314A: Global MASTER-Net observations report
  96. Fermi GRB 260313A: Global MASTER-Net observations report
  97. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  98. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  99. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  100. GRB 260312B: AstroSat CZTI detection

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