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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"

44194 results found.

  1. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  2. GRB 260401A: SVOM/GRM observation
  3. GRB 260401A: GECAM-B observation
  4. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  5. GRB 260402A: Kilonova-Catcher optical upper limit
  6. GRB 260402A: MASTER optical observations
  7. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  8. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  9. GRB 260402A: SVOM detection of a burst
  10. Fermi GRB 260401A: Global MASTER-Net observations report
  11. GRB 260401A: Fermi GBM Observation
  12. GRB 260401A: NuSTAR detection of prompt emission
  13. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  14. GRB 260401A: MAXI/GSC detection
  15. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  16. GRB 260401A: Fermi GBM Final Real-time Localization
  17. EP260329b: Mondy and Assy-Turgen optical upper limits
  18. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  19. EP260321a :Xinglong optical observations
  20. EP260327a: Xinglong optical upper limit
  21. EP260329b: GOTO detection of optical counterpart
  22. GRB 260330B: SVOM/VT optical upper limits
  23. Konus-Wind detection of GRB 260320A
  24. Konus-Wind detection of GRB 260316B (duplicate submission)
  25. Konus-Wind detection of GRB 260316B
  26. GRB 260321A: SVOM/ECLAIRs refined analysis
  27. EP260329b: J-band upper limits with WINTER
  28. EP260329a: J-band upper limit with WINTER
  29. GRB 260330A: Glowbug gamma-ray detection
  30. GRB 260310A: VLA Multi-frequency Radio Observations
  31. Fermi GBM Sub-Threshold Detection of GRB 260330B
  32. GRB 260330B: LCO optical upper limits
  33. GRB 260330B: SVOM detection of a burst
  34. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  35. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  36. EP260329a: COLIBRÍ optical upper limit
  37. EP260329a: EP-FXT follow up observation
  38. EP260329a: NOT optical counterpart candidate
  39. GRB 260330A: Fermi GBM Final Real-time Localization
  40. EP260329b: Global MASTER-Net observations report
  41. Fermi trigger No 796485221: Global MASTER-Net observations report
  42. GRB 260327A: Insight-HXMT/HE detection
  43. EP260329b: Optical follow-up with Kinder observations
  44. EP 260329b: COLIBRÍ optical observations
  45. EP260329a: Optical upper limit with Kinder observations
  46. EP260329b: LCO optical observations of the counterpart
  47. GRB 260326A: Insight-HXMT/HE detection
  48. EP260329b: Einstein Probe detection of an X-ray transient
  49. EP260329a: Einstein Probe detection of an X-ray transient
  50. EP-WXT trigger 01709259209: TRT optical counterpart detection
  51. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  52. GRID detection of GRB 260326A
  53. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  54. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  55. EP260327a: SVOM/VT optical upper limits
  56. SMA Detection of GRB 260310A / AT 2026fgk
  57. GRB 260307B: ATCA Radio Upper Limits
  58. EP260327a: WINTER J-band upper limit
  59. EP260327a: COLIBRÍ optical upper limits
  60. GRB 260327A: AstroSat CZTI detection of a long burst
  61. EP260327a: Gemini-North optical upper limits
  62. EP260324a: GROWTH-India Telescope optical observation
  63. EP260327a: Global MASTER-Net observations report
  64. EP260327a: Einstein Probe detection of an X-ray transient
  65. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  66. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  67. The EP-WXT trigger 01709259173 is likely a flaring star
  68. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  69. IPN triangulation of GRB 260320A
  70. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  71. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  72. GRB 260326A: Fermi GBM Detection
  73. EP260321a: JinShan near-infrared observations
  74. GRB 260325A: Fermi GBM Final Localization
  75. GRB 260326A: Fermi GBM Final Real-time Localization
  76. EP260321a: Upper limits from a neutrino search with IceCube
  77. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  78. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  79. IPN triangulation of GRB 260316B
  80. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  81. GRID detection of GRB 260320A
  82. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  83. EP260321a: Gemini-South confirmation of a supernova
  84. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  85. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  86. GRB 260310A: LBT optical observations
  87. EP260321A: Mondy optical observations
  88. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  89. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  90. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  91. The EP-WXT trigger 01709259112 is likely a flaring star
  92. Fermi GRB 260323A: Global MASTER-Net observations report
  93. GRB 260323A: Fermi GBM Final Real-time Localization
  94. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  95. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  96. GRB 260322A: Fermi GBM Final Localization
  97. GRB 260320A: Glowbug gamma-ray detection
  98. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  99. EP260321a: COLIBRÍ further optical observations and brightening
  100. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB

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