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

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