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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"

38618 results found.

  1. GRB 260402A: MASTER optical observations
  2. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  3. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  4. GRB 260402A: SVOM detection of a burst
  5. GRB 260401A: Fermi GBM Observation
  6. GRB 260401A: NuSTAR detection of prompt emission
  7. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  8. GRB 260401A: MAXI/GSC detection
  9. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  10. GRB 260401A: Fermi GBM Final Real-time Localization
  11. EP260329b: Mondy and Assy-Turgen optical upper limits
  12. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  13. EP260321a :Xinglong optical observations
  14. EP260327a: Xinglong optical upper limit
  15. EP260329b: GOTO detection of optical counterpart
  16. GRB 260330B: SVOM/VT optical upper limits
  17. Konus-Wind detection of GRB 260320A
  18. Konus-Wind detection of GRB 260316B
  19. GRB 260321A: SVOM/ECLAIRs refined analysis
  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. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  26. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  27. EP260329a: COLIBRÍ optical upper limit
  28. EP260329a: EP-FXT follow up observation
  29. GRB 260330A: Fermi GBM Final Real-time Localization
  30. GRB 260327A: Insight-HXMT/HE detection
  31. EP260329b: Optical follow-up with Kinder observations
  32. EP 260329b: COLIBRÍ optical observations
  33. EP260329a: Optical upper limit with Kinder observations
  34. EP260329b: LCO optical observations of the counterpart
  35. GRB 260326A: Insight-HXMT/HE detection
  36. EP260329b: Einstein Probe detection of an X-ray transient
  37. EP260329a: Einstein Probe detection of an X-ray transient
  38. EP-WXT trigger 01709259209: TRT optical counterpart detection
  39. GRID detection of GRB 260326A
  40. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  41. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  42. EP260327a: SVOM/VT optical upper limits
  43. SMA Detection of GRB 260310A / AT 2026fgk
  44. GRB 260307B: ATCA Radio Upper Limits
  45. EP260327a: WINTER J-band upper limit
  46. EP260327a: COLIBRÍ optical upper limits
  47. GRB 260327A: AstroSat CZTI detection of a long burst
  48. EP260327a: Gemini-North optical upper limits
  49. EP260324a: GROWTH-India Telescope optical observation
  50. EP260327a: Einstein Probe detection of an X-ray transient
  51. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  52. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  53. The EP-WXT trigger 01709259173 is likely a flaring star
  54. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  55. IPN triangulation of GRB 260320A
  56. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  57. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  58. GRB 260326A: Fermi GBM Detection
  59. GRB 260325A: Fermi GBM Final Localization
  60. GRB 260326A: Fermi GBM Final Real-time Localization
  61. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  62. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  63. IPN triangulation of GRB 260316B
  64. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  65. GRID detection of GRB 260320A
  66. EP260321a: Gemini-South confirmation of a supernova
  67. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  68. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  69. GRB 260310A: LBT optical observations
  70. EP260321A: Mondy optical observations
  71. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  72. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  73. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  74. The EP-WXT trigger 01709259112 is likely a flaring star
  75. GRB 260323A: Fermi GBM Final Real-time Localization
  76. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  77. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  78. GRB 260322A: Fermi GBM Final Localization
  79. GRB 260320A: Glowbug gamma-ray detection
  80. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  81. EP260321a: COLIBRÍ further optical observations and brightening
  82. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  83. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  84. EP260214b: ATCA 6 GHz detection
  85. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  86. GRB 260321A: EP-FXT follow-up observation
  87. The EP-WXT trigger 01709259045 is likely a flaring star
  88. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  89. EP260321a: GOTO detection of blue variable source
  90. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  91. EP260321a: further Kinder optical observations
  92. GRB 260321A: SVOM/VT optical upper limits
  93. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  94. GRB 260320A: Insight-HXMT/HE detection
  95. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  96. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  97. EP260321a: SVOM/VT optical upper limit
  98. GRB 260310A: continued optical observation at Mondy
  99. Fermi GBM Sub-Threshold Detection of GRB 260321A
  100. GRB 260321A: SVOM detection of a burst

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