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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"

28103 results found.

  1. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  2. EP260409a: COLIBRÍ optical upper limits
  3. EP260409a: Global MASTER-Net observations report
  4. EP260409a: Einstein Probe detection of an X-ray transient
  5. EP260321a: VLA radio detection
  6. GRB 260407A: Glowbug gamma-ray detection
  7. GRB 260402A: SVOM/ECLAIRs refined analysis
  8. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  9. EP260402a / GRB 260402A: Mephisto optical upper limits
  10. EP-WXT01709259586: Xinglong optical upper limit
  11. EP260403a: Mephisto optical upper limits
  12. EP260402a/GRB 260402A: Xinglong optical upper limit
  13. EP260405a: GMOS-N optical upper limits
  14. EP260405a: Global MASTER-Net observations report
  15. EP260405a: Einstein Probe detection of a fast X-ray transient
  16. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  17. Fermi trigger No 797039833: Global MASTER-Net observations report
  18. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  19. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  20. The EP-WXT trigger 01709259586 is likely a flaring star
  21. GRB 260330B: SVOM/VT further optical observation
  22. EP260403a: LCO optical observations of the counterpart
  23. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  24. EP260403a: LCO optical counterpart detection
  25. EP260403a: COLIBRÍ optical counterpart candidate
  26. GRB 260330B: SVOM/VT optical candidate
  27. EP260403a: Einstein Probe detection of an X-ray transient
  28. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  29. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  30. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  31. GRB 260402C: NuSTAR detection of prompt emission
  32. GRB 260402C: AstroSat CZTI detection of a long burst
  33. EP260324A / AT 2026hir: COLIBRÍ optical observations
  34. GRB 260402A: WINTER J-band upper limit
  35. GRB260402A: GROWTH-India Telescope optical upper limit
  36. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  37. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  38. GRB 260401A: SVOM/GRM observation
  39. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  40. GRB 260402A: Kilonova-Catcher optical upper limit
  41. GRB 260402A: MASTER optical observations
  42. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  43. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  44. GRB 260402A: SVOM detection of a burst
  45. Fermi GRB 260401A: Global MASTER-Net observations report
  46. GRB 260401A: Fermi GBM Observation
  47. GRB 260401A: NuSTAR detection of prompt emission
  48. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  49. GRB 260401A: MAXI/GSC detection
  50. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  51. GRB 260401A: Fermi GBM Final Real-time Localization
  52. EP260329b: Mondy and Assy-Turgen optical upper limits
  53. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  54. EP260321a :Xinglong optical observations
  55. EP260327a: Xinglong optical upper limit
  56. GRB 260330B: SVOM/VT optical upper limits
  57. Konus-Wind detection of GRB 260320A
  58. GRB 260321A: SVOM/ECLAIRs refined analysis
  59. EP260329b: J-band upper limits with WINTER
  60. EP260329a: J-band upper limit with WINTER
  61. GRB 260330A: Glowbug gamma-ray detection
  62. Fermi GBM Sub-Threshold Detection of GRB 260330B
  63. GRB 260330B: LCO optical upper limits
  64. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  65. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  66. EP260329a: COLIBRÍ optical upper limit
  67. EP260329a: EP-FXT follow up observation
  68. EP260329a: NOT optical counterpart candidate
  69. EP260329b: Global MASTER-Net observations report
  70. Fermi trigger No 796485221: Global MASTER-Net observations report
  71. GRB 260327A: Insight-HXMT/HE detection
  72. EP260329b: Optical follow-up with Kinder observations
  73. EP 260329b: COLIBRÍ optical observations
  74. EP260329a: Optical upper limit with Kinder observations
  75. EP260329b: LCO optical observations of the counterpart
  76. GRB 260326A: Insight-HXMT/HE detection
  77. EP260329b: Einstein Probe detection of an X-ray transient
  78. EP260329a: Einstein Probe detection of an X-ray transient
  79. EP-WXT trigger 01709259209: TRT optical counterpart detection
  80. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  81. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  82. EP260327a: SVOM/VT optical upper limits
  83. EP260327a: WINTER J-band upper limit
  84. EP260327a: COLIBRÍ optical upper limits
  85. EP260327a: Gemini-North optical upper limits
  86. EP260324a: GROWTH-India Telescope optical observation
  87. EP260327a: Global MASTER-Net observations report
  88. EP260327a: Einstein Probe detection of an X-ray transient
  89. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  90. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  91. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  92. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  93. GRB 260326A: Fermi GBM Detection
  94. EP260321a: JinShan near-infrared observations
  95. EP260321a: Upper limits from a neutrino search with IceCube
  96. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  97. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  98. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  99. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  100. Fermi GRB 260323A: Global MASTER-Net observations report

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