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

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