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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

28109 results found.

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

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