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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"

37148 results found.

  1. Konus-Wind detection of GRB 260316B
  2. GRB 260321A: SVOM/ECLAIRs refined analysis
  3. EP260329b: J-band upper limits with WINTER
  4. EP260329a: J-band upper limit with WINTER
  5. GRB 260330A: Glowbug gamma-ray detection
  6. GRB 260310A: VLA Multi-frequency Radio Observations
  7. Fermi GBM Sub-Threshold Detection of GRB 260330B
  8. GRB 260330B: LCO optical upper limits
  9. GRB 260330B: SVOM detection of a burst
  10. GRB 260330A: Fermi GBM Final Real-time Localization
  11. GRB 260327A: Insight-HXMT/HE detection
  12. EP260329b: Optical follow-up with Kinder observations
  13. EP260329a: Optical upper limit with Kinder observations
  14. GRB 260326A: Insight-HXMT/HE detection
  15. GRID detection of GRB 260326A
  16. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  17. SMA Detection of GRB 260310A / AT 2026fgk
  18. GRB 260307B: ATCA Radio Upper Limits
  19. GRB 260327A: AstroSat CZTI detection of a long burst
  20. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  21. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  22. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  23. IPN triangulation of GRB 260320A
  24. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  25. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  26. GRB 260326A: Fermi GBM Detection
  27. GRB 260325A: Fermi GBM Final Localization
  28. GRB 260326A: Fermi GBM Final Real-time Localization
  29. EP260321a: Upper limits from a neutrino search with IceCube
  30. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  31. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  32. IPN triangulation of GRB 260316B
  33. GRID detection of GRB 260320A
  34. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  35. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  36. GRB 260310A: LBT optical observations
  37. EP260321A: Mondy optical observations
  38. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  39. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  40. Fermi GRB 260323A: Global MASTER-Net observations report
  41. GRB 260323A: Fermi GBM Final Real-time Localization
  42. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  43. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  44. GRB 260322A: Fermi GBM Final Localization
  45. GRB 260320A: Glowbug gamma-ray detection
  46. EP260321a: COLIBRÍ further optical observations and brightening
  47. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  48. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  49. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  50. GRB 260321A: EP-FXT follow-up observation
  51. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  52. EP260321a: further Kinder optical observations
  53. GRB 260321A: SVOM/VT optical upper limits
  54. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  55. GRB 260320A: Insight-HXMT/HE detection
  56. GRB 260310A: continued optical observation at Mondy
  57. Fermi GBM Sub-Threshold Detection of GRB 260321A
  58. GRB 260321A: SVOM detection of a burst
  59. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  60. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  61. GRB 260318A: Glowbug gamma-ray detection
  62. GRB 260310A / AT 2026fgk: KAIT optical observations
  63. GRB 260320A: NuSTAR detection of prompt emission
  64. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  65. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  66. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  67. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  68. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  69. GRB 260310A/AT2026fgk: LBT near-infrared observations
  70. NOEMA Detection of GRB 260310A / AT 2026fgk
  71. GRB 260318A: SVOM/GRM observation
  72. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  73. GRB 260318A: GECAM-B observation
  74. Fermi GRB 260318A: Global MASTER-Net observations report
  75. GRB 260318A: Fermi GBM Final Real-time Localization
  76. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  77. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  78. GRB 260310A / AT 2026fgk: radio detection with the VLA
  79. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  80. GRB 260310A / AT2026fgk: LCO optical observations
  81. GRB 260317A: Fermi GBM Final Localization
  82. GRB 260316B: GECAM-B observation
  83. GRB 260316B: SVOM/GRM observation
  84. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  85. GRB 260316B: AstroSat CZTI detection
  86. GRB 260316B: Fermi GBM Final Real-time Localization
  87. EP260316a: optical upper limit with Kinder observations
  88. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  89. GRB 260314A: Glowbug gamma-ray detection
  90. EP260314a: optical upper limit with Kinder observations
  91. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  92. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  93. GRB 260310A / AT 2026fgk: iTelescope optical observations
  94. GRID detection of GRB 260312B
  95. EP260314a: BOOTES-6/DPR optical upper limits at early times
  96. GRB 260314A: GECAM-B observation of a burst
  97. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  98. GRB 260310A / AT2026fgk: SAO RAS optical observations
  99. GRB 260310A/AT2026fgk: radio detection at 15GHz
  100. GRB 260310A / AT2026fgk: TNG NIR detection

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