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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"

43615 results found.

  1. Konus-Wind detection of GRB 260320A
  2. Konus-Wind detection of GRB 260316B (duplicate submission)
  3. Konus-Wind detection of GRB 260316B
  4. GRB 260321A: SVOM/ECLAIRs refined analysis
  5. EP260329b: J-band upper limits with WINTER
  6. EP260329a: J-band upper limit with WINTER
  7. GRB 260330A: Glowbug gamma-ray detection
  8. GRB 260310A: VLA Multi-frequency Radio Observations
  9. Fermi GBM Sub-Threshold Detection of GRB 260330B
  10. GRB 260330B: LCO optical upper limits
  11. GRB 260330B: SVOM detection of a burst
  12. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  13. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  14. EP260329a: COLIBRÍ optical upper limit
  15. EP260329a: EP-FXT follow up observation
  16. EP260329a: NOT optical counterpart candidate
  17. GRB 260330A: Fermi GBM Final Real-time Localization
  18. EP260329b: Global MASTER-Net observations report
  19. Fermi trigger No 796485221: Global MASTER-Net observations report
  20. GRB 260327A: Insight-HXMT/HE detection
  21. EP260329b: Optical follow-up with Kinder observations
  22. EP 260329b: COLIBRÍ optical observations
  23. EP260329a: Optical upper limit with Kinder observations
  24. EP260329b: LCO optical observations of the counterpart
  25. GRB 260326A: Insight-HXMT/HE detection
  26. EP260329b: Einstein Probe detection of an X-ray transient
  27. EP260329a: Einstein Probe detection of an X-ray transient
  28. EP-WXT trigger 01709259209: TRT optical counterpart detection
  29. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  30. GRID detection of GRB 260326A
  31. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  32. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  33. EP260327a: SVOM/VT optical upper limits
  34. SMA Detection of GRB 260310A / AT 2026fgk
  35. GRB 260307B: ATCA Radio Upper Limits
  36. EP260327a: WINTER J-band upper limit
  37. EP260327a: COLIBRÍ optical upper limits
  38. GRB 260327A: AstroSat CZTI detection of a long burst
  39. EP260327a: Gemini-North optical upper limits
  40. EP260324a: GROWTH-India Telescope optical observation
  41. EP260327a: Global MASTER-Net observations report
  42. EP260327a: Einstein Probe detection of an X-ray transient
  43. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  44. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  45. The EP-WXT trigger 01709259173 is likely a flaring star
  46. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  47. IPN triangulation of GRB 260320A
  48. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  49. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  50. GRB 260326A: Fermi GBM Detection
  51. EP260321a: JinShan near-infrared observations
  52. GRB 260325A: Fermi GBM Final Localization
  53. GRB 260326A: Fermi GBM Final Real-time Localization
  54. EP260321a: Upper limits from a neutrino search with IceCube
  55. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  56. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  57. IPN triangulation of GRB 260316B
  58. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  59. GRID detection of GRB 260320A
  60. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  61. EP260321a: Gemini-South confirmation of a supernova
  62. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  63. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  64. GRB 260310A: LBT optical observations
  65. EP260321A: Mondy optical observations
  66. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  67. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  68. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  69. The EP-WXT trigger 01709259112 is likely a flaring star
  70. Fermi GRB 260323A: Global MASTER-Net observations report
  71. GRB 260323A: Fermi GBM Final Real-time Localization
  72. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  73. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  74. GRB 260322A: Fermi GBM Final Localization
  75. GRB 260320A: Glowbug gamma-ray detection
  76. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  77. EP260321a: COLIBRÍ further optical observations and brightening
  78. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  79. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  80. EP260214b: ATCA 6 GHz detection
  81. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  82. GRB 260321A: EP-FXT follow-up observation
  83. The EP-WXT trigger 01709259045 is likely a flaring star
  84. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  85. EP260321a: GOTO detection of blue variable source
  86. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  87. EP260321a: further Kinder optical observations
  88. GRB 260321A: SVOM/VT optical upper limits
  89. EP260321a: Las Cumbres upper limit
  90. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  91. GRB 260320A: Insight-HXMT/HE detection
  92. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  93. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  94. EP260321a: SVOM/VT optical upper limit
  95. GRB 260310A: continued optical observation at Mondy
  96. Fermi GBM Sub-Threshold Detection of GRB 260321A
  97. GRB 260321A: SVOM detection of a burst
  98. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  99. EP260321a: Global MASTER-Net observations report
  100. EP260321a: Einstein Probe detection of an X-ray transient

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