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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"

31634 results found.

  1. EP-WXT01709259586: Xinglong optical upper limit
  2. EP260403a: Mephisto optical upper limits
  3. EP260402a/GRB 260402A: Xinglong optical upper limit
  4. EP260321a: Upper limits from VLA radio observations
  5. GRID detection of GRB 260401A
  6. EP260321a: uGMRT observations
  7. EP260405a: GMOS-N optical upper limits
  8. EP260405a: SVOM/VT optical upper limits
  9. EP260405a: Global MASTER-Net observations report
  10. EP260405a: Einstein Probe detection of a fast X-ray transient
  11. GRB 260403A: GECAM-B observation of a long burst
  12. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  13. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  14. GRB 260330B: SVOM/VT further optical observation
  15. GRB 260330B: SVOM/ECLAIRs refined analysis
  16. EP260403a: LCO optical observations of the counterpart
  17. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  18. EP260403a: LCO optical counterpart detection
  19. EP260403a: COLIBRÍ optical counterpart candidate
  20. GRB 260330B: SVOM/VT optical candidate
  21. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  22. GRB 260403A: AstroSat CZTI detection
  23. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  24. GRB 260402B: GECAM-B observation
  25. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  26. GRB 260402C: NuSTAR detection of prompt emission
  27. EP260324A / AT 2026hir: COLIBRÍ optical observations
  28. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  29. GRB 260402A: WINTER J-band upper limit
  30. GRB260402A: GROWTH-India Telescope optical upper limit
  31. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  32. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  33. GRB 260401A: SVOM/GRM observation
  34. GRB 260401A: GECAM-B observation
  35. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  36. GRB 260402A: Kilonova-Catcher optical upper limit
  37. GRB 260402A: MASTER optical observations
  38. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  39. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  40. Fermi GRB 260401A: Global MASTER-Net observations report
  41. GRB 260401A: Fermi GBM Observation
  42. GRB 260401A: NuSTAR detection of prompt emission
  43. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  44. GRB 260401A: MAXI/GSC detection
  45. EP260329b: Mondy and Assy-Turgen optical upper limits
  46. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  47. EP260321a :Xinglong optical observations
  48. EP260327a: Xinglong optical upper limit
  49. EP260329b: GOTO detection of optical counterpart
  50. GRB 260330B: SVOM/VT optical upper limits
  51. Konus-Wind detection of GRB 260320A
  52. Konus-Wind detection of GRB 260316B (duplicate submission)
  53. Konus-Wind detection of GRB 260316B
  54. GRB 260321A: SVOM/ECLAIRs refined analysis
  55. EP260329b: J-band upper limits with WINTER
  56. EP260329a: J-band upper limit with WINTER
  57. GRB 260330A: Glowbug gamma-ray detection
  58. GRB 260310A: VLA Multi-frequency Radio Observations
  59. Fermi GBM Sub-Threshold Detection of GRB 260330B
  60. GRB 260330B: LCO optical upper limits
  61. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  62. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  63. EP260329a: COLIBRÍ optical upper limit
  64. EP260329a: EP-FXT follow up observation
  65. EP260329a: NOT optical counterpart candidate
  66. EP260329b: Global MASTER-Net observations report
  67. GRB 260327A: Insight-HXMT/HE detection
  68. EP260329b: Optical follow-up with Kinder observations
  69. EP 260329b: COLIBRÍ optical observations
  70. EP260329a: Optical upper limit with Kinder observations
  71. EP260329b: LCO optical observations of the counterpart
  72. GRB 260326A: Insight-HXMT/HE detection
  73. EP260329b: Einstein Probe detection of an X-ray transient
  74. EP-WXT trigger 01709259209: TRT optical counterpart detection
  75. GRID detection of GRB 260326A
  76. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  77. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  78. EP260327a: SVOM/VT optical upper limits
  79. SMA Detection of GRB 260310A / AT 2026fgk
  80. GRB 260307B: ATCA Radio Upper Limits
  81. EP260327a: WINTER J-band upper limit
  82. EP260327a: COLIBRÍ optical upper limits
  83. EP260327a: Gemini-North optical upper limits
  84. EP260324a: GROWTH-India Telescope optical observation
  85. EP260327a: Global MASTER-Net observations report
  86. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  87. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  88. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  89. IPN triangulation of GRB 260320A
  90. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  91. GRB 260326A: Fermi GBM Detection
  92. EP260321a: JinShan near-infrared observations
  93. EP260321a: Upper limits from a neutrino search with IceCube
  94. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  95. IPN triangulation of GRB 260316B
  96. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  97. GRID detection of GRB 260320A
  98. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  99. EP260321a: Gemini-South confirmation of a supernova
  100. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf

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