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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"

31731 results found.

  1. GRID detection of GRB 260401A
  2. EP260321a: uGMRT observations
  3. EP260405a: GMOS-N optical upper limits
  4. EP260405a: SVOM/VT optical upper limits
  5. EP260405a: Global MASTER-Net observations report
  6. EP260405a: Einstein Probe detection of a fast X-ray transient
  7. GRB 260403A: GECAM-B observation of a long burst
  8. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  9. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  10. GRB 260330B: SVOM/VT further optical observation
  11. GRB 260330B: SVOM/ECLAIRs refined analysis
  12. EP260403a: LCO optical observations of the counterpart
  13. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  14. EP260403a: LCO optical counterpart detection
  15. EP260403a: COLIBRÍ optical counterpart candidate
  16. GRB 260330B: SVOM/VT optical candidate
  17. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  18. GRB 260403A: AstroSat CZTI detection
  19. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  20. GRB 260402B: GECAM-B observation
  21. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  22. GRB 260402C: NuSTAR detection of prompt emission
  23. EP260324A / AT 2026hir: COLIBRÍ optical observations
  24. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  25. GRB 260402A: WINTER J-band upper limit
  26. GRB260402A: GROWTH-India Telescope optical upper limit
  27. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  28. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  29. GRB 260401A: SVOM/GRM observation
  30. GRB 260401A: GECAM-B observation
  31. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  32. GRB 260402A: Kilonova-Catcher optical upper limit
  33. GRB 260402A: MASTER optical observations
  34. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  35. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  36. Fermi GRB 260401A: Global MASTER-Net observations report
  37. GRB 260401A: Fermi GBM Observation
  38. GRB 260401A: NuSTAR detection of prompt emission
  39. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  40. GRB 260401A: MAXI/GSC detection
  41. EP260329b: Mondy and Assy-Turgen optical upper limits
  42. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  43. EP260321a :Xinglong optical observations
  44. EP260327a: Xinglong optical upper limit
  45. EP260329b: GOTO detection of optical counterpart
  46. GRB 260330B: SVOM/VT optical upper limits
  47. Konus-Wind detection of GRB 260320A
  48. Konus-Wind detection of GRB 260316B (duplicate submission)
  49. Konus-Wind detection of GRB 260316B
  50. GRB 260321A: SVOM/ECLAIRs refined analysis
  51. EP260329b: J-band upper limits with WINTER
  52. EP260329a: J-band upper limit with WINTER
  53. GRB 260330A: Glowbug gamma-ray detection
  54. GRB 260310A: VLA Multi-frequency Radio Observations
  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. GRB 260327A: Insight-HXMT/HE detection
  64. EP260329b: Optical follow-up with Kinder observations
  65. EP 260329b: COLIBRÍ optical observations
  66. EP260329a: Optical upper limit with Kinder observations
  67. EP260329b: LCO optical observations of the counterpart
  68. GRB 260326A: Insight-HXMT/HE detection
  69. EP260329b: Einstein Probe detection of an X-ray transient
  70. EP-WXT trigger 01709259209: TRT optical counterpart detection
  71. GRID detection of GRB 260326A
  72. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  73. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  74. EP260327a: SVOM/VT optical upper limits
  75. SMA Detection of GRB 260310A / AT 2026fgk
  76. GRB 260307B: ATCA Radio Upper Limits
  77. EP260327a: WINTER J-band upper limit
  78. EP260327a: COLIBRÍ optical upper limits
  79. EP260327a: Gemini-North optical upper limits
  80. EP260324a: GROWTH-India Telescope optical observation
  81. EP260327a: Global MASTER-Net observations report
  82. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  83. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  84. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  85. IPN triangulation of GRB 260320A
  86. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  87. GRB 260326A: Fermi GBM Detection
  88. EP260321a: JinShan near-infrared observations
  89. EP260321a: Upper limits from a neutrino search with IceCube
  90. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  91. IPN triangulation of GRB 260316B
  92. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  93. GRID detection of GRB 260320A
  94. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  95. EP260321a: Gemini-South confirmation of a supernova
  96. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  97. GRB 260310A: LBT optical observations
  98. EP260321A: Mondy optical observations
  99. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  100. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7

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