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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"

35426 results found.

  1. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  2. GRB 260402C: NuSTAR detection of prompt emission
  3. GRB 260402C: AstroSat CZTI detection of a long burst
  4. GRB 260403A: Fermi GBM Final Real-time Localization
  5. GRB 260402B: Fermi GBM Final Real-time Localization
  6. GRB 260402A: WINTER J-band upper limit
  7. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  8. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  9. GRB 260401A: SVOM/GRM observation
  10. GRB 260401A: GECAM-B observation
  11. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  12. GRB 260402A: Kilonova-Catcher optical upper limit
  13. GRB 260402A: MASTER optical observations
  14. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  15. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  16. GRB 260402A: SVOM detection of a burst
  17. Fermi GRB 260401A: Global MASTER-Net observations report
  18. GRB 260401A: Fermi GBM Observation
  19. GRB 260401A: NuSTAR detection of prompt emission
  20. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  21. GRB 260401A: MAXI/GSC detection
  22. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  23. GRB 260401A: Fermi GBM Final Real-time Localization
  24. EP260329b: Mondy and Assy-Turgen optical upper limits
  25. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  26. EP260329b: GOTO detection of optical counterpart
  27. GRB 260330B: SVOM/VT optical upper limits
  28. Konus-Wind detection of GRB 260320A
  29. Konus-Wind detection of GRB 260316B (duplicate submission)
  30. Konus-Wind detection of GRB 260316B
  31. GRB 260321A: SVOM/ECLAIRs refined analysis
  32. EP260329b: J-band upper limits with WINTER
  33. EP260329a: J-band upper limit with WINTER
  34. GRB 260330A: Glowbug gamma-ray detection
  35. GRB 260310A: VLA Multi-frequency Radio Observations
  36. Fermi GBM Sub-Threshold Detection of GRB 260330B
  37. GRB 260330B: LCO optical upper limits
  38. GRB 260330B: SVOM detection of a burst
  39. GRB 260330A: Fermi GBM Final Real-time Localization
  40. GRB 260327A: Insight-HXMT/HE detection
  41. GRB 260326A: Insight-HXMT/HE detection
  42. GRID detection of GRB 260326A
  43. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  44. SMA Detection of GRB 260310A / AT 2026fgk
  45. GRB 260307B: ATCA Radio Upper Limits
  46. GRB 260327A: AstroSat CZTI detection of a long burst
  47. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  48. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  49. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  50. IPN triangulation of GRB 260320A
  51. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  52. GRB 260326A: Fermi GBM Detection
  53. GRB 260325A: Fermi GBM Final Localization
  54. GRB 260326A: Fermi GBM Final Real-time Localization
  55. EP260321a: Upper limits from a neutrino search with IceCube
  56. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  57. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  58. IPN triangulation of GRB 260316B
  59. GRID detection of GRB 260320A
  60. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  61. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  62. GRB 260310A: LBT optical observations
  63. EP260321A: Mondy optical observations
  64. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  65. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  66. Fermi GRB 260323A: Global MASTER-Net observations report
  67. GRB 260323A: Fermi GBM Final Real-time Localization
  68. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  69. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  70. GRB 260322A: Fermi GBM Final Localization
  71. GRB 260320A: Glowbug gamma-ray detection
  72. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  73. GRB 260321A: EP-FXT follow-up observation
  74. GRB 260321A: SVOM/VT optical upper limits
  75. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  76. GRB 260320A: Insight-HXMT/HE detection
  77. GRB 260310A: continued optical observation at Mondy
  78. Fermi GBM Sub-Threshold Detection of GRB 260321A
  79. GRB 260321A: SVOM detection of a burst
  80. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  81. GRB 260318A: Glowbug gamma-ray detection
  82. GRB 260310A / AT 2026fgk: KAIT optical observations
  83. GRB 260320A: NuSTAR detection of prompt emission
  84. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  85. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  86. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  87. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  88. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  89. GRB 260310A/AT2026fgk: LBT near-infrared observations
  90. NOEMA Detection of GRB 260310A / AT 2026fgk
  91. GRB 260318A: SVOM/GRM observation
  92. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  93. GRB 260318A: GECAM-B observation
  94. Fermi GRB 260318A: Global MASTER-Net observations report
  95. GRB 260318A: Fermi GBM Final Real-time Localization
  96. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  97. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  98. GRB 260310A / AT 2026fgk: radio detection with the VLA
  99. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  100. GRB 260310A / AT2026fgk: LCO optical observations

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