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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"

27090 results found.

  1. EP260402a / GRB 260402A: Mephisto optical upper limits
  2. EP-WXT01709259586: Xinglong optical upper limit
  3. EP260403a: Mephisto optical upper limits
  4. EP260402a/GRB 260402A: Xinglong optical upper limit
  5. EP260405a: GMOS-N optical upper limits
  6. EP260405a: Global MASTER-Net observations report
  7. EP260405a: Einstein Probe detection of a fast X-ray transient
  8. EP260405.149 / EP-WXT 11900672904: COLIBRÍ optical upper limits
  9. Fermi trigger No 797039833: Global MASTER-Net observations report
  10. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  11. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  12. The EP-WXT trigger 01709259586 is likely a flaring star
  13. GRB 260330B: SVOM/VT further optical observation
  14. EP260403a: LCO optical observations of the counterpart
  15. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  16. EP260403a: LCO optical counterpart detection
  17. EP260403a: COLIBRÍ optical counterpart candidate
  18. GRB 260330B: SVOM/VT optical candidate
  19. EP260403a: Einstein Probe detection of an X-ray transient
  20. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  21. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  22. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  23. GRB 260402C: NuSTAR detection of prompt emission
  24. GRB 260402C: AstroSat CZTI detection of a long burst
  25. EP260324A / AT 2026hir: COLIBRÍ optical observations
  26. GRB 260402A: WINTER J-band upper limit
  27. GRB260402A: GROWTH-India Telescope optical upper limit
  28. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  29. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  30. GRB 260401A: SVOM/GRM observation
  31. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  32. GRB 260402A: Kilonova-Catcher optical upper limit
  33. GRB 260402A: MASTER optical observations
  34. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  35. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  36. GRB 260402A: SVOM detection of a burst
  37. Fermi GRB 260401A: Global MASTER-Net observations report
  38. GRB 260401A: Fermi GBM Observation
  39. GRB 260401A: NuSTAR detection of prompt emission
  40. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  41. GRB 260401A: MAXI/GSC detection
  42. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  43. GRB 260401A: Fermi GBM Final Real-time Localization
  44. EP260329b: Mondy and Assy-Turgen optical upper limits
  45. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  46. EP260321a :Xinglong optical observations
  47. EP260327a: Xinglong optical upper limit
  48. GRB 260330B: SVOM/VT optical upper limits
  49. Konus-Wind detection of GRB 260320A
  50. GRB 260321A: SVOM/ECLAIRs refined analysis
  51. EP260329b: J-band upper limits with WINTER
  52. EP260329a: J-band upper limit with WINTER
  53. GRB 260330A: Glowbug gamma-ray detection
  54. Fermi GBM Sub-Threshold Detection of GRB 260330B
  55. GRB 260330B: LCO optical upper limits
  56. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  57. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  58. EP260329a: COLIBRÍ optical upper limit
  59. EP260329a: EP-FXT follow up observation
  60. EP260329a: NOT optical counterpart candidate
  61. EP260329b: Global MASTER-Net observations report
  62. Fermi trigger No 796485221: Global MASTER-Net observations report
  63. GRB 260327A: Insight-HXMT/HE detection
  64. EP260329b: Optical follow-up with Kinder observations
  65. EP 260329b: COLIBRÍ optical observations
  66. EP260329a: Optical upper limit with Kinder observations
  67. EP260329b: LCO optical observations of the counterpart
  68. GRB 260326A: Insight-HXMT/HE detection
  69. EP260329b: Einstein Probe detection of an X-ray transient
  70. EP260329a: Einstein Probe detection of an X-ray transient
  71. EP-WXT trigger 01709259209: TRT optical counterpart detection
  72. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  73. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  74. EP260327a: SVOM/VT optical upper limits
  75. EP260327a: WINTER J-band upper limit
  76. EP260327a: COLIBRÍ optical upper limits
  77. EP260327a: Gemini-North optical upper limits
  78. EP260324a: GROWTH-India Telescope optical observation
  79. EP260327a: Global MASTER-Net observations report
  80. EP260327a: Einstein Probe detection of an X-ray transient
  81. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  82. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  83. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  84. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  85. GRB 260326A: Fermi GBM Detection
  86. EP260321a: JinShan near-infrared observations
  87. EP260321a: Upper limits from a neutrino search with IceCube
  88. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  89. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  90. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  91. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  92. Fermi GRB 260323A: Global MASTER-Net observations report
  93. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  94. GRB 260320A: Glowbug gamma-ray detection
  95. EP260321a: COLIBRÍ further optical observations and brightening
  96. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  97. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  98. GRB 260321A: EP-FXT follow-up observation
  99. EP260321a: GOTO detection of blue variable source
  100. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343

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