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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"

31636 results found.

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

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