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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"

28045 results found.

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

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