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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

45895 results found.

  1. GRB 260403A: GECAM-B observation of a long burst
  2. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  3. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  4. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  5. The EP-WXT trigger 01709259586 is likely a flaring star
  6. GRB 260330B: SVOM/VT further optical observation
  7. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  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. EP260403a: Einstein Probe detection of an X-ray transient
  15. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  16. GRB 260403A: AstroSat CZTI detection
  17. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  18. GRB 260402B: GECAM-B observation
  19. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  20. GRB 260402C: NuSTAR detection of prompt emission
  21. GRB 260402C: AstroSat CZTI detection of a long burst
  22. EP260324A / AT 2026hir: COLIBRÍ optical observations
  23. GRB 260403A: Fermi GBM Final Real-time Localization
  24. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  25. GRB 260402B: Fermi GBM Final Real-time Localization
  26. GRB 260402A: WINTER J-band upper limit
  27. GRB260402A: GROWTH-India Telescope optical upper limit
  28. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  29. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  30. GRB 260401A: SVOM/GRM observation
  31. GRB 260401A: GECAM-B observation
  32. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  33. GRB 260402A: Kilonova-Catcher optical upper limit
  34. GRB 260402A: MASTER optical observations
  35. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  36. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  37. GRB 260402A: SVOM detection of a burst
  38. Fermi GRB 260401A: Global MASTER-Net observations report
  39. GRB 260401A: Fermi GBM Observation
  40. GRB 260401A: NuSTAR detection of prompt emission
  41. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  42. GRB 260401A: MAXI/GSC detection
  43. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  44. GRB 260401A: Fermi GBM Final Real-time Localization
  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. GRB 260330B: SVOM detection of a burst
  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. GRB 260330A: Fermi GBM Final Real-time Localization
  68. EP260329b: Global MASTER-Net observations report
  69. Fermi trigger No 796485221: Global MASTER-Net observations report
  70. GRB 260327A: Insight-HXMT/HE detection
  71. EP260329b: Optical follow-up with Kinder observations
  72. EP 260329b: COLIBRÍ optical observations
  73. EP260329a: Optical upper limit with Kinder observations
  74. EP260329b: LCO optical observations of the counterpart
  75. GRB 260326A: Insight-HXMT/HE detection
  76. EP260329b: Einstein Probe detection of an X-ray transient
  77. EP260329a: Einstein Probe detection of an X-ray transient
  78. EP-WXT trigger 01709259209: TRT optical counterpart detection
  79. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  80. GRID detection of GRB 260326A
  81. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  82. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  83. EP260327a: SVOM/VT optical upper limits
  84. SMA Detection of GRB 260310A / AT 2026fgk
  85. GRB 260307B: ATCA Radio Upper Limits
  86. EP260327a: WINTER J-band upper limit
  87. EP260327a: COLIBRÍ optical upper limits
  88. GRB 260327A: AstroSat CZTI detection of a long burst
  89. EP260327a: Gemini-North optical upper limits
  90. EP260324a: GROWTH-India Telescope optical observation
  91. EP260327a: Global MASTER-Net observations report
  92. EP260327a: Einstein Probe detection of an X-ray transient
  93. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  94. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  95. The EP-WXT trigger 01709259173 is likely a flaring star
  96. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  97. IPN triangulation of GRB 260320A
  98. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  99. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  100. GRB 260326A: Fermi GBM Detection

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