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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"

27317 results found.

  1. Fermi GRB 260413A: Global MASTER-Net observations report
  2. GRB 260410A: Glowbug gamma-ray detection of a short burst
  3. Fermi GRB 260412A: Global MASTER-Net observations report
  4. GRB 260412A: Fermi GBM Observation
  5. GRB 260411B: Fermi-LAT detection
  6. GRB 260411B: COLIBRÍ optical observations
  7. GRB 260410B: Fermi GBM Observation
  8. GRB260411B: 3.6m DOT optical observation
  9. GRB 260411A: SVOM/GRM observation
  10. GRB 260411B: SVOM/GRM observation of a long burst
  11. GRB 260409A: Insight-HXMT/HE detection
  12. GRB 260411B: Fermi GBM Detection
  13. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  14. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  15. GRB 260410A: COLIBRÍ optical upper limit
  16. EP-WXT01709259790: Optical Upper limits with kinder observations
  17. GRB 260410A: Fermi GBM Observation
  18. GRB 260410B: SVOM/GRM detection of a short faint burst
  19. EP-WXT01709259790: Xinglong optical upper limit
  20. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  21. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  22. EP260409a: COLIBRÍ optical upper limits
  23. EP260409a: Global MASTER-Net observations report
  24. EP260409a: Einstein Probe detection of an X-ray transient
  25. EP260321a: VLA radio detection
  26. GRB 260407A: Glowbug gamma-ray detection
  27. GRB 260402A: SVOM/ECLAIRs refined analysis
  28. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  29. EP260402a / GRB 260402A: Mephisto optical upper limits
  30. EP-WXT01709259586: Xinglong optical upper limit
  31. EP260403a: Mephisto optical upper limits
  32. EP260402a/GRB 260402A: Xinglong optical upper limit
  33. EP260405a: GMOS-N optical upper limits
  34. EP260405a: Global MASTER-Net observations report
  35. EP260405a: Einstein Probe detection of a fast X-ray transient
  36. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  37. Fermi trigger No 797039833: Global MASTER-Net observations report
  38. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  39. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  40. The EP-WXT trigger 01709259586 is likely a flaring star
  41. GRB 260330B: SVOM/VT further optical observation
  42. EP260403a: LCO optical observations of the counterpart
  43. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  44. EP260403a: LCO optical counterpart detection
  45. EP260403a: COLIBRÍ optical counterpart candidate
  46. GRB 260330B: SVOM/VT optical candidate
  47. EP260403a: Einstein Probe detection of an X-ray transient
  48. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  49. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  50. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  51. GRB 260402C: NuSTAR detection of prompt emission
  52. GRB 260402C: AstroSat CZTI detection of a long burst
  53. EP260324A / AT 2026hir: COLIBRÍ optical observations
  54. GRB 260402A: WINTER J-band upper limit
  55. GRB260402A: GROWTH-India Telescope optical upper limit
  56. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  57. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  58. GRB 260401A: SVOM/GRM observation
  59. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  60. GRB 260402A: Kilonova-Catcher optical upper limit
  61. GRB 260402A: MASTER optical observations
  62. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  63. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  64. GRB 260402A: SVOM detection of a burst
  65. Fermi GRB 260401A: Global MASTER-Net observations report
  66. GRB 260401A: Fermi GBM Observation
  67. GRB 260401A: NuSTAR detection of prompt emission
  68. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  69. GRB 260401A: MAXI/GSC detection
  70. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  71. GRB 260401A: Fermi GBM Final Real-time Localization
  72. EP260329b: Mondy and Assy-Turgen optical upper limits
  73. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  74. EP260321a :Xinglong optical observations
  75. EP260327a: Xinglong optical upper limit
  76. GRB 260330B: SVOM/VT optical upper limits
  77. Konus-Wind detection of GRB 260320A
  78. GRB 260321A: SVOM/ECLAIRs refined analysis
  79. EP260329b: J-band upper limits with WINTER
  80. EP260329a: J-band upper limit with WINTER
  81. GRB 260330A: Glowbug gamma-ray detection
  82. Fermi GBM Sub-Threshold Detection of GRB 260330B
  83. GRB 260330B: LCO optical upper limits
  84. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  85. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  86. EP260329a: COLIBRÍ optical upper limit
  87. EP260329a: EP-FXT follow up observation
  88. EP260329a: NOT optical counterpart candidate
  89. EP260329b: Global MASTER-Net observations report
  90. Fermi trigger No 796485221: Global MASTER-Net observations report
  91. GRB 260327A: Insight-HXMT/HE detection
  92. EP260329b: Optical follow-up with Kinder observations
  93. EP 260329b: COLIBRÍ optical observations
  94. EP260329a: Optical upper limit with Kinder observations
  95. EP260329b: LCO optical observations of the counterpart
  96. GRB 260326A: Insight-HXMT/HE detection
  97. EP260329b: Einstein Probe detection of an X-ray transient
  98. EP260329a: Einstein Probe detection of an X-ray transient
  99. EP-WXT trigger 01709259209: TRT optical counterpart detection
  100. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart

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