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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"
  1. GRB 260330B: SVOM/VT further optical observation
  2. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  3. GRB 260330B: SVOM/ECLAIRs refined analysis
  4. EP260403a: LCO optical observations of the counterpart
  5. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  6. EP260403a: LCO optical counterpart detection
  7. EP260403a: COLIBRÍ optical counterpart candidate
  8. GRB 260330B: SVOM/VT optical candidate
  9. EP260403a: Einstein Probe detection of an X-ray transient
  10. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  11. GRB 260403A: AstroSat CZTI detection
  12. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  13. GRB 260402B: GECAM-B observation
  14. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  15. GRB 260402C: NuSTAR detection of prompt emission
  16. GRB 260402C: AstroSat CZTI detection of a long burst
  17. EP260324A / AT 2026hir: COLIBRÍ optical observations
  18. GRB 260403A: Fermi GBM Final Real-time Localization
  19. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  20. GRB 260402B: Fermi GBM Final Real-time Localization
  21. GRB 260402A: WINTER J-band upper limit
  22. GRB260402A: GROWTH-India Telescope optical upper limit
  23. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  24. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  25. GRB 260401A: SVOM/GRM observation
  26. GRB 260401A: GECAM-B observation
  27. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  28. GRB 260402A: Kilonova-Catcher optical upper limit
  29. GRB 260402A: MASTER optical observations
  30. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  31. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  32. GRB 260402A: SVOM detection of a burst
  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. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  39. GRB 260401A: Fermi GBM Final Real-time Localization
  40. EP260329b: Mondy and Assy-Turgen optical upper limits
  41. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  42. EP260321a :Xinglong optical observations
  43. EP260327a: Xinglong optical upper limit
  44. EP260329b: GOTO detection of optical counterpart
  45. GRB 260330B: SVOM/VT optical upper limits
  46. Konus-Wind detection of GRB 260320A
  47. Konus-Wind detection of GRB 260316B (duplicate submission)
  48. Konus-Wind detection of GRB 260316B
  49. GRB 260321A: SVOM/ECLAIRs refined analysis
  50. EP260329b: J-band upper limits with WINTER
  51. EP260329a: J-band upper limit with WINTER
  52. GRB 260330A: Glowbug gamma-ray detection
  53. GRB 260310A: VLA Multi-frequency Radio Observations
  54. Fermi GBM Sub-Threshold Detection of GRB 260330B
  55. GRB 260330B: LCO optical upper limits
  56. GRB 260330B: SVOM detection of a burst
  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. GRB 260330A: Fermi GBM Final Real-time Localization
  63. EP260329b: Global MASTER-Net observations report
  64. Fermi trigger No 796485221: Global MASTER-Net observations report
  65. GRB 260327A: Insight-HXMT/HE detection
  66. EP260329b: Optical follow-up with Kinder observations
  67. EP 260329b: COLIBRÍ optical observations
  68. EP260329a: Optical upper limit with Kinder observations
  69. EP260329b: LCO optical observations of the counterpart
  70. GRB 260326A: Insight-HXMT/HE detection
  71. EP260329b: Einstein Probe detection of an X-ray transient
  72. EP260329a: Einstein Probe detection of an X-ray transient
  73. EP-WXT trigger 01709259209: TRT optical counterpart detection
  74. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  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. GRB 260327A: AstroSat CZTI detection of a long burst
  84. EP260327a: Gemini-North optical upper limits
  85. EP260324a: GROWTH-India Telescope optical observation
  86. EP260327a: Global MASTER-Net observations report
  87. EP260327a: Einstein Probe detection of an X-ray transient
  88. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  89. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  90. The EP-WXT trigger 01709259173 is likely a flaring star
  91. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  92. IPN triangulation of GRB 260320A
  93. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  94. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  95. GRB 260326A: Fermi GBM Detection
  96. EP260321a: JinShan near-infrared observations
  97. GRB 260325A: Fermi GBM Final Localization
  98. GRB 260326A: Fermi GBM Final Real-time Localization
  99. EP260321a: Upper limits from a neutrino search with IceCube
  100. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB

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