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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"

28087 results found.

  1. EP260405a: Global MASTER-Net observations report
  2. EP260405a: Einstein Probe detection of a fast X-ray transient
  3. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  4. Fermi trigger No 797039833: Global MASTER-Net observations report
  5. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  6. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  7. The EP-WXT trigger 01709259586 is likely a flaring star
  8. GRB 260330B: SVOM/VT further optical observation
  9. EP260403a: LCO optical observations of the counterpart
  10. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  11. EP260403a: LCO optical counterpart detection
  12. EP260403a: COLIBRÍ optical counterpart candidate
  13. GRB 260330B: SVOM/VT optical candidate
  14. EP260403a: Einstein Probe detection of an X-ray transient
  15. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  16. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  17. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  18. GRB 260402C: NuSTAR detection of prompt emission
  19. GRB 260402C: AstroSat CZTI detection of a long burst
  20. EP260324A / AT 2026hir: COLIBRÍ optical observations
  21. GRB 260402A: WINTER J-band upper limit
  22. GRB260402A: GROWTH-India Telescope optical upper limit
  23. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  24. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  25. GRB 260401A: SVOM/GRM observation
  26. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  27. GRB 260402A: Kilonova-Catcher optical upper limit
  28. GRB 260402A: MASTER optical observations
  29. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  30. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  31. GRB 260402A: SVOM detection of a burst
  32. Fermi GRB 260401A: Global MASTER-Net observations report
  33. GRB 260401A: Fermi GBM Observation
  34. GRB 260401A: NuSTAR detection of prompt emission
  35. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  36. GRB 260401A: MAXI/GSC detection
  37. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  38. GRB 260401A: Fermi GBM Final Real-time Localization
  39. EP260329b: Mondy and Assy-Turgen optical upper limits
  40. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  41. EP260321a :Xinglong optical observations
  42. EP260327a: Xinglong optical upper limit
  43. GRB 260330B: SVOM/VT optical upper limits
  44. Konus-Wind detection of GRB 260320A
  45. GRB 260321A: SVOM/ECLAIRs refined analysis
  46. EP260329b: J-band upper limits with WINTER
  47. EP260329a: J-band upper limit with WINTER
  48. GRB 260330A: Glowbug gamma-ray detection
  49. Fermi GBM Sub-Threshold Detection of GRB 260330B
  50. GRB 260330B: LCO optical upper limits
  51. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  52. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  53. EP260329a: COLIBRÍ optical upper limit
  54. EP260329a: EP-FXT follow up observation
  55. EP260329a: NOT optical counterpart candidate
  56. EP260329b: Global MASTER-Net observations report
  57. Fermi trigger No 796485221: Global MASTER-Net observations report
  58. GRB 260327A: Insight-HXMT/HE detection
  59. EP260329b: Optical follow-up with Kinder observations
  60. EP 260329b: COLIBRÍ optical observations
  61. EP260329a: Optical upper limit with Kinder observations
  62. EP260329b: LCO optical observations of the counterpart
  63. GRB 260326A: Insight-HXMT/HE detection
  64. EP260329b: Einstein Probe detection of an X-ray transient
  65. EP260329a: Einstein Probe detection of an X-ray transient
  66. EP-WXT trigger 01709259209: TRT optical counterpart detection
  67. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  68. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  69. EP260327a: SVOM/VT optical upper limits
  70. EP260327a: WINTER J-band upper limit
  71. EP260327a: COLIBRÍ optical upper limits
  72. EP260327a: Gemini-North optical upper limits
  73. EP260324a: GROWTH-India Telescope optical observation
  74. EP260327a: Global MASTER-Net observations report
  75. EP260327a: Einstein Probe detection of an X-ray transient
  76. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  77. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  78. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  79. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  80. GRB 260326A: Fermi GBM Detection
  81. EP260321a: JinShan near-infrared observations
  82. EP260321a: Upper limits from a neutrino search with IceCube
  83. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  84. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  85. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  86. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  87. Fermi GRB 260323A: Global MASTER-Net observations report
  88. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  89. GRB 260320A: Glowbug gamma-ray detection
  90. EP260321a: COLIBRÍ further optical observations and brightening
  91. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  92. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  93. GRB 260321A: EP-FXT follow-up observation
  94. EP260321a: GOTO detection of blue variable source
  95. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  96. EP260321a: further Kinder optical observations
  97. GRB 260321A: SVOM/VT optical upper limits
  98. EP260321a: Las Cumbres upper limit
  99. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  100. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission

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