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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"

31727 results found.

  1. EP260405a: SVOM/VT optical upper limits
  2. EP260405a: Global MASTER-Net observations report
  3. EP260405a: Einstein Probe detection of a fast X-ray transient
  4. GRB 260403A: GECAM-B observation of a long burst
  5. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  6. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  7. GRB 260330B: SVOM/VT further optical observation
  8. GRB 260330B: SVOM/ECLAIRs refined analysis
  9. EP260403a: LCO optical observations of the counterpart
  10. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  11. EP260403a: LCO optical counterpart detection
  12. EP260403a: COLIBRÍ optical counterpart candidate
  13. GRB 260330B: SVOM/VT optical candidate
  14. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  15. GRB 260403A: AstroSat CZTI detection
  16. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  17. GRB 260402B: GECAM-B observation
  18. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  19. GRB 260402C: NuSTAR detection of prompt emission
  20. EP260324A / AT 2026hir: COLIBRÍ optical observations
  21. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  22. GRB 260402A: WINTER J-band upper limit
  23. GRB260402A: GROWTH-India Telescope optical upper limit
  24. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  25. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  26. GRB 260401A: SVOM/GRM observation
  27. GRB 260401A: GECAM-B observation
  28. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  29. GRB 260402A: Kilonova-Catcher optical upper limit
  30. GRB 260402A: MASTER optical observations
  31. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  32. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  33. Fermi GRB 260401A: Global MASTER-Net observations report
  34. GRB 260401A: Fermi GBM Observation
  35. GRB 260401A: NuSTAR detection of prompt emission
  36. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  37. GRB 260401A: MAXI/GSC detection
  38. EP260329b: Mondy and Assy-Turgen optical upper limits
  39. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  40. EP260321a :Xinglong optical observations
  41. EP260327a: Xinglong optical upper limit
  42. EP260329b: GOTO detection of optical counterpart
  43. GRB 260330B: SVOM/VT optical upper limits
  44. Konus-Wind detection of GRB 260320A
  45. Konus-Wind detection of GRB 260316B (duplicate submission)
  46. Konus-Wind detection of GRB 260316B
  47. GRB 260321A: SVOM/ECLAIRs refined analysis
  48. EP260329b: J-band upper limits with WINTER
  49. EP260329a: J-band upper limit with WINTER
  50. GRB 260330A: Glowbug gamma-ray detection
  51. GRB 260310A: VLA Multi-frequency Radio Observations
  52. Fermi GBM Sub-Threshold Detection of GRB 260330B
  53. GRB 260330B: LCO optical upper limits
  54. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  55. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  56. EP260329a: COLIBRÍ optical upper limit
  57. EP260329a: EP-FXT follow up observation
  58. EP260329a: NOT optical counterpart candidate
  59. EP260329b: Global MASTER-Net observations report
  60. GRB 260327A: Insight-HXMT/HE detection
  61. EP260329b: Optical follow-up with Kinder observations
  62. EP 260329b: COLIBRÍ optical observations
  63. EP260329a: Optical upper limit with Kinder observations
  64. EP260329b: LCO optical observations of the counterpart
  65. GRB 260326A: Insight-HXMT/HE detection
  66. EP260329b: Einstein Probe detection of an X-ray transient
  67. EP-WXT trigger 01709259209: TRT optical counterpart detection
  68. GRID detection of GRB 260326A
  69. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  70. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  71. EP260327a: SVOM/VT optical upper limits
  72. SMA Detection of GRB 260310A / AT 2026fgk
  73. GRB 260307B: ATCA Radio Upper Limits
  74. EP260327a: WINTER J-band upper limit
  75. EP260327a: COLIBRÍ optical upper limits
  76. EP260327a: Gemini-North optical upper limits
  77. EP260324a: GROWTH-India Telescope optical observation
  78. EP260327a: Global MASTER-Net observations report
  79. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  80. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  81. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  82. IPN triangulation of GRB 260320A
  83. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  84. GRB 260326A: Fermi GBM Detection
  85. EP260321a: JinShan near-infrared observations
  86. EP260321a: Upper limits from a neutrino search with IceCube
  87. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  88. IPN triangulation of GRB 260316B
  89. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  90. GRID detection of GRB 260320A
  91. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  92. EP260321a: Gemini-South confirmation of a supernova
  93. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  94. GRB 260310A: LBT optical observations
  95. EP260321A: Mondy optical observations
  96. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  97. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  98. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  99. Fermi GRB 260323A: Global MASTER-Net observations report
  100. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days

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