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