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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"

40744 results found.

  1. Fermi GRB 260401A: Global MASTER-Net observations report
  2. GRB 260401A: Fermi GBM Observation
  3. GRB 260401A: NuSTAR detection of prompt emission
  4. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  5. GRB 260401A: MAXI/GSC detection
  6. EP260329b: Mondy and Assy-Turgen optical upper limits
  7. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  8. EP260321a :Xinglong optical observations
  9. EP260327a: Xinglong optical upper limit
  10. EP260329b: GOTO detection of optical counterpart
  11. GRB 260330B: SVOM/VT optical upper limits
  12. Konus-Wind detection of GRB 260320A
  13. Konus-Wind detection of GRB 260316B (duplicate submission)
  14. Konus-Wind detection of GRB 260316B
  15. GRB 260321A: SVOM/ECLAIRs refined analysis
  16. EP260329b: J-band upper limits with WINTER
  17. EP260329a: J-band upper limit with WINTER
  18. GRB 260330A: Glowbug gamma-ray detection
  19. GRB 260310A: VLA Multi-frequency Radio Observations
  20. Fermi GBM Sub-Threshold Detection of GRB 260330B
  21. GRB 260330B: LCO optical upper limits
  22. GRB 260330B: SVOM detection of a burst
  23. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  24. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  25. EP260329a: COLIBRÍ optical upper limit
  26. EP260329a: EP-FXT follow up observation
  27. EP260329a: NOT optical counterpart candidate
  28. EP260329b: Global MASTER-Net observations report
  29. Fermi trigger No 796485221: Global MASTER-Net observations report
  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. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  40. GRID detection of GRB 260326A
  41. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  42. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  43. EP260327a: SVOM/VT optical upper limits
  44. SMA Detection of GRB 260310A / AT 2026fgk
  45. GRB 260307B: ATCA Radio Upper Limits
  46. EP260327a: WINTER J-band upper limit
  47. EP260327a: COLIBRÍ optical upper limits
  48. GRB 260327A: AstroSat CZTI detection of a long burst
  49. EP260327a: Gemini-North optical upper limits
  50. EP260324a: GROWTH-India Telescope optical observation
  51. EP260327a: Global MASTER-Net observations report
  52. EP260327a: Einstein Probe detection of an X-ray transient
  53. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  54. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  55. The EP-WXT trigger 01709259173 is likely a flaring star
  56. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  57. IPN triangulation of GRB 260320A
  58. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  59. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  60. GRB 260326A: Fermi GBM Detection
  61. EP260321a: JinShan near-infrared observations
  62. EP260321a: Upper limits from a neutrino search with IceCube
  63. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  64. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  65. IPN triangulation of GRB 260316B
  66. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  67. GRID detection of GRB 260320A
  68. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  69. EP260321a: Gemini-South confirmation of a supernova
  70. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  71. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  72. GRB 260310A: LBT optical observations
  73. EP260321A: Mondy optical observations
  74. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  75. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  76. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  77. The EP-WXT trigger 01709259112 is likely a flaring star
  78. Fermi GRB 260323A: Global MASTER-Net observations report
  79. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  80. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  81. GRB 260320A: Glowbug gamma-ray detection
  82. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  83. EP260321a: COLIBRÍ further optical observations and brightening
  84. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  85. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  86. EP260214b: ATCA 6 GHz detection
  87. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  88. GRB 260321A: EP-FXT follow-up observation
  89. The EP-WXT trigger 01709259045 is likely a flaring star
  90. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  91. EP260321a: GOTO detection of blue variable source
  92. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  93. EP260321a: further Kinder optical observations
  94. GRB 260321A: SVOM/VT optical upper limits
  95. EP260321a: Las Cumbres upper limit
  96. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  97. GRB 260320A: Insight-HXMT/HE detection
  98. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  99. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  100. EP260321a: SVOM/VT optical upper limit

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