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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"

36313 results found.

  1. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  2. GRB 260402A: SVOM detection of a burst
  3. Fermi GRB 260401A: Global MASTER-Net observations report
  4. GRB 260401A: Fermi GBM Observation
  5. GRB 260401A: NuSTAR detection of prompt emission
  6. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  7. GRB 260401A: MAXI/GSC detection
  8. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  9. GRB 260401A: Fermi GBM Final Real-time Localization
  10. EP260329b: Mondy and Assy-Turgen optical upper limits
  11. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  12. EP260329b: GOTO detection of optical counterpart
  13. GRB 260330B: SVOM/VT optical upper limits
  14. Konus-Wind detection of GRB 260320A
  15. Konus-Wind detection of GRB 260316B (duplicate submission)
  16. Konus-Wind detection of GRB 260316B
  17. GRB 260321A: SVOM/ECLAIRs refined analysis
  18. EP260329b: J-band upper limits with WINTER
  19. EP260329a: J-band upper limit with WINTER
  20. GRB 260330A: Glowbug gamma-ray detection
  21. GRB 260310A: VLA Multi-frequency Radio Observations
  22. Fermi GBM Sub-Threshold Detection of GRB 260330B
  23. GRB 260330B: LCO optical upper limits
  24. GRB 260330B: SVOM detection of a burst
  25. GRB 260330A: Fermi GBM Final Real-time Localization
  26. GRB 260327A: Insight-HXMT/HE detection
  27. GRB 260326A: Insight-HXMT/HE detection
  28. GRID detection of GRB 260326A
  29. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  30. SMA Detection of GRB 260310A / AT 2026fgk
  31. GRB 260307B: ATCA Radio Upper Limits
  32. GRB 260327A: AstroSat CZTI detection of a long burst
  33. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  34. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  35. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  36. IPN triangulation of GRB 260320A
  37. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  38. GRB 260326A: Fermi GBM Detection
  39. GRB 260325A: Fermi GBM Final Localization
  40. GRB 260326A: Fermi GBM Final Real-time Localization
  41. EP260321a: Upper limits from a neutrino search with IceCube
  42. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  43. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  44. IPN triangulation of GRB 260316B
  45. GRID detection of GRB 260320A
  46. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  47. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  48. GRB 260310A: LBT optical observations
  49. EP260321A: Mondy optical observations
  50. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  51. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  52. Fermi GRB 260323A: Global MASTER-Net observations report
  53. GRB 260323A: Fermi GBM Final Real-time Localization
  54. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  55. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  56. GRB 260322A: Fermi GBM Final Localization
  57. GRB 260320A: Glowbug gamma-ray detection
  58. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  59. GRB 260321A: EP-FXT follow-up observation
  60. GRB 260321A: SVOM/VT optical upper limits
  61. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  62. GRB 260320A: Insight-HXMT/HE detection
  63. GRB 260310A: continued optical observation at Mondy
  64. Fermi GBM Sub-Threshold Detection of GRB 260321A
  65. GRB 260321A: SVOM detection of a burst
  66. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  67. GRB 260318A: Glowbug gamma-ray detection
  68. GRB 260310A / AT 2026fgk: KAIT optical observations
  69. GRB 260320A: NuSTAR detection of prompt emission
  70. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  71. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  72. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  73. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  74. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  75. GRB 260310A/AT2026fgk: LBT near-infrared observations
  76. NOEMA Detection of GRB 260310A / AT 2026fgk
  77. GRB 260318A: SVOM/GRM observation
  78. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  79. GRB 260318A: GECAM-B observation
  80. Fermi GRB 260318A: Global MASTER-Net observations report
  81. GRB 260318A: Fermi GBM Final Real-time Localization
  82. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  83. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  84. GRB 260310A / AT 2026fgk: radio detection with the VLA
  85. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  86. GRB 260310A / AT2026fgk: LCO optical observations
  87. GRB 260317A: Fermi GBM Final Localization
  88. GRB 260316B: GECAM-B observation
  89. GRB 260316B: SVOM/GRM observation
  90. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  91. GRB 260316B: AstroSat CZTI detection
  92. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  93. GRB 260316B: Fermi GBM Final Real-time Localization
  94. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  95. GRB 260314A: Glowbug gamma-ray detection
  96. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  97. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  98. GRB 260310A / AT 2026fgk: iTelescope optical observations
  99. GRID detection of GRB 260312B
  100. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event

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