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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. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  2. GRB 260402B: GECAM-B observation
  3. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  4. GRB 260402C: NuSTAR detection of prompt emission
  5. GRB 260402C: AstroSat CZTI detection of a long burst
  6. EP260324A / AT 2026hir: COLIBRÍ optical observations
  7. GRB 260403A: Fermi GBM Final Real-time Localization
  8. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  9. GRB 260402B: Fermi GBM Final Real-time Localization
  10. GRB 260402A: WINTER J-band upper limit
  11. GRB260402A: GROWTH-India Telescope optical upper limit
  12. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  13. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  14. GRB 260401A: SVOM/GRM observation
  15. GRB 260401A: GECAM-B observation
  16. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  17. GRB 260402A: Kilonova-Catcher optical upper limit
  18. GRB 260402A: MASTER optical observations
  19. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  20. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  21. GRB 260402A: SVOM detection of a burst
  22. Fermi GRB 260401A: Global MASTER-Net observations report
  23. GRB 260401A: Fermi GBM Observation
  24. GRB 260401A: NuSTAR detection of prompt emission
  25. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  26. GRB 260401A: MAXI/GSC detection
  27. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  28. GRB 260401A: Fermi GBM Final Real-time Localization
  29. EP260329b: Mondy and Assy-Turgen optical upper limits
  30. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  31. EP260321a :Xinglong optical observations
  32. EP260327a: Xinglong optical upper limit
  33. EP260329b: GOTO detection of optical counterpart
  34. GRB 260330B: SVOM/VT optical upper limits
  35. Konus-Wind detection of GRB 260320A
  36. Konus-Wind detection of GRB 260316B (duplicate submission)
  37. Konus-Wind detection of GRB 260316B
  38. GRB 260321A: SVOM/ECLAIRs refined analysis
  39. EP260329b: J-band upper limits with WINTER
  40. EP260329a: J-band upper limit with WINTER
  41. GRB 260330A: Glowbug gamma-ray detection
  42. GRB 260310A: VLA Multi-frequency Radio Observations
  43. Fermi GBM Sub-Threshold Detection of GRB 260330B
  44. GRB 260330B: LCO optical upper limits
  45. GRB 260330B: SVOM detection of a burst
  46. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  47. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  48. EP260329a: COLIBRÍ optical upper limit
  49. EP260329a: EP-FXT follow up observation
  50. EP260329a: NOT optical counterpart candidate
  51. GRB 260330A: Fermi GBM Final Real-time Localization
  52. EP260329b: Global MASTER-Net observations report
  53. Fermi trigger No 796485221: Global MASTER-Net observations report
  54. GRB 260327A: Insight-HXMT/HE detection
  55. EP260329b: Optical follow-up with Kinder observations
  56. EP 260329b: COLIBRÍ optical observations
  57. EP260329a: Optical upper limit with Kinder observations
  58. EP260329b: LCO optical observations of the counterpart
  59. GRB 260326A: Insight-HXMT/HE detection
  60. EP260329b: Einstein Probe detection of an X-ray transient
  61. EP260329a: Einstein Probe detection of an X-ray transient
  62. EP-WXT trigger 01709259209: TRT optical counterpart detection
  63. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  64. GRID detection of GRB 260326A
  65. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  66. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  67. EP260327a: SVOM/VT optical upper limits
  68. SMA Detection of GRB 260310A / AT 2026fgk
  69. GRB 260307B: ATCA Radio Upper Limits
  70. EP260327a: WINTER J-band upper limit
  71. EP260327a: COLIBRÍ optical upper limits
  72. GRB 260327A: AstroSat CZTI detection of a long burst
  73. EP260327a: Gemini-North optical upper limits
  74. EP260324a: GROWTH-India Telescope optical observation
  75. EP260327a: Global MASTER-Net observations report
  76. EP260327a: Einstein Probe detection of an X-ray transient
  77. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  78. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  79. The EP-WXT trigger 01709259173 is likely a flaring star
  80. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  81. IPN triangulation of GRB 260320A
  82. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  83. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  84. GRB 260326A: Fermi GBM Detection
  85. EP260321a: JinShan near-infrared observations
  86. GRB 260325A: Fermi GBM Final Localization
  87. GRB 260326A: Fermi GBM Final Real-time Localization
  88. EP260321a: Upper limits from a neutrino search with IceCube
  89. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  90. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  91. IPN triangulation of GRB 260316B
  92. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  93. GRID detection of GRB 260320A
  94. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  95. EP260321a: Gemini-South confirmation of a supernova
  96. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  97. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  98. GRB 260310A: LBT optical observations
  99. EP260321A: Mondy optical observations
  100. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions

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