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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"

31633 results found.

  1. EP260402a/GRB 260402A: Xinglong optical upper limit
  2. EP260321a: Upper limits from VLA radio observations
  3. GRID detection of GRB 260401A
  4. EP260321a: uGMRT observations
  5. EP260405a: GMOS-N optical upper limits
  6. EP260405a: SVOM/VT optical upper limits
  7. EP260405a: Global MASTER-Net observations report
  8. EP260405a: Einstein Probe detection of a fast X-ray transient
  9. GRB 260403A: GECAM-B observation of a long burst
  10. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  11. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  12. GRB 260330B: SVOM/VT further optical observation
  13. GRB 260330B: SVOM/ECLAIRs refined analysis
  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. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  20. GRB 260403A: AstroSat CZTI detection
  21. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  22. GRB 260402B: GECAM-B observation
  23. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  24. GRB 260402C: NuSTAR detection of prompt emission
  25. EP260324A / AT 2026hir: COLIBRÍ optical observations
  26. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  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. GRB 260401A: GECAM-B observation
  33. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  34. GRB 260402A: Kilonova-Catcher optical upper limit
  35. GRB 260402A: MASTER optical observations
  36. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  37. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  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. EP260329b: Mondy and Assy-Turgen optical upper limits
  44. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  45. EP260321a :Xinglong optical observations
  46. EP260327a: Xinglong optical upper limit
  47. EP260329b: GOTO detection of optical counterpart
  48. GRB 260330B: SVOM/VT optical upper limits
  49. Konus-Wind detection of GRB 260320A
  50. Konus-Wind detection of GRB 260316B (duplicate submission)
  51. Konus-Wind detection of GRB 260316B
  52. GRB 260321A: SVOM/ECLAIRs refined analysis
  53. EP260329b: J-band upper limits with WINTER
  54. EP260329a: J-band upper limit with WINTER
  55. GRB 260330A: Glowbug gamma-ray detection
  56. GRB 260310A: VLA Multi-frequency Radio Observations
  57. Fermi GBM Sub-Threshold Detection of GRB 260330B
  58. GRB 260330B: LCO optical upper limits
  59. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  60. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  61. EP260329a: COLIBRÍ optical upper limit
  62. EP260329a: EP-FXT follow up observation
  63. EP260329a: NOT optical counterpart candidate
  64. EP260329b: Global MASTER-Net observations report
  65. GRB 260327A: Insight-HXMT/HE detection
  66. EP260329b: Optical follow-up with Kinder observations
  67. EP 260329b: COLIBRÍ optical observations
  68. EP260329a: Optical upper limit with Kinder observations
  69. EP260329b: LCO optical observations of the counterpart
  70. GRB 260326A: Insight-HXMT/HE detection
  71. EP260329b: Einstein Probe detection of an X-ray transient
  72. EP-WXT trigger 01709259209: TRT optical counterpart detection
  73. GRID detection of GRB 260326A
  74. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  75. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  76. EP260327a: SVOM/VT optical upper limits
  77. SMA Detection of GRB 260310A / AT 2026fgk
  78. GRB 260307B: ATCA Radio Upper Limits
  79. EP260327a: WINTER J-band upper limit
  80. EP260327a: COLIBRÍ optical upper limits
  81. EP260327a: Gemini-North optical upper limits
  82. EP260324a: GROWTH-India Telescope optical observation
  83. EP260327a: Global MASTER-Net observations report
  84. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  85. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  86. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  87. IPN triangulation of GRB 260320A
  88. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  89. GRB 260326A: Fermi GBM Detection
  90. EP260321a: JinShan near-infrared observations
  91. EP260321a: Upper limits from a neutrino search with IceCube
  92. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  93. IPN triangulation of GRB 260316B
  94. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  95. GRID detection of GRB 260320A
  96. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  97. EP260321a: Gemini-South confirmation of a supernova
  98. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  99. GRB 260310A: LBT optical observations
  100. EP260321A: Mondy optical observations

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