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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"

27390 results found.

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

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