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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

32722 results found.

  1. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  2. GRB 260330B: SVOM/VT further optical observation
  3. GRB 260330B: SVOM/ECLAIRs refined analysis
  4. EP260403a: LCO optical observations of the counterpart
  5. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  6. EP260403a: LCO optical counterpart detection
  7. EP260403a: COLIBRÍ optical counterpart candidate
  8. GRB 260330B: SVOM/VT optical candidate
  9. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  10. GRB 260403A: AstroSat CZTI detection
  11. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  12. GRB 260402B: GECAM-B observation
  13. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  14. GRB 260402C: NuSTAR detection of prompt emission
  15. EP260324A / AT 2026hir: COLIBRÍ optical observations
  16. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  17. GRB 260402A: WINTER J-band upper limit
  18. GRB260402A: GROWTH-India Telescope optical upper limit
  19. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  20. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  21. GRB 260401A: SVOM/GRM observation
  22. GRB 260401A: GECAM-B observation
  23. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  24. GRB 260402A: Kilonova-Catcher optical upper limit
  25. GRB 260402A: MASTER optical observations
  26. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  27. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  28. Fermi GRB 260401A: Global MASTER-Net observations report
  29. GRB 260401A: Fermi GBM Observation
  30. GRB 260401A: NuSTAR detection of prompt emission
  31. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  32. GRB 260401A: MAXI/GSC detection
  33. EP260329b: Mondy and Assy-Turgen optical upper limits
  34. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  35. EP260321a :Xinglong optical observations
  36. EP260327a: Xinglong optical upper limit
  37. EP260329b: GOTO detection of optical counterpart
  38. GRB 260330B: SVOM/VT optical upper limits
  39. Konus-Wind detection of GRB 260320A
  40. Konus-Wind detection of GRB 260316B (duplicate submission)
  41. Konus-Wind detection of GRB 260316B
  42. GRB 260321A: SVOM/ECLAIRs refined analysis
  43. EP260329b: J-band upper limits with WINTER
  44. EP260329a: J-band upper limit with WINTER
  45. GRB 260330A: Glowbug gamma-ray detection
  46. GRB 260310A: VLA Multi-frequency Radio Observations
  47. Fermi GBM Sub-Threshold Detection of GRB 260330B
  48. GRB 260330B: LCO optical upper limits
  49. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  50. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  51. EP260329a: COLIBRÍ optical upper limit
  52. EP260329a: EP-FXT follow up observation
  53. EP260329a: NOT optical counterpart candidate
  54. EP260329b: Global MASTER-Net observations report
  55. GRB 260327A: Insight-HXMT/HE detection
  56. EP260329b: Optical follow-up with Kinder observations
  57. EP 260329b: COLIBRÍ optical observations
  58. EP260329a: Optical upper limit with Kinder observations
  59. EP260329b: LCO optical observations of the counterpart
  60. GRB 260326A: Insight-HXMT/HE detection
  61. EP260329b: Einstein Probe detection of an X-ray transient
  62. EP-WXT trigger 01709259209: TRT optical counterpart detection
  63. GRID detection of GRB 260326A
  64. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  65. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  66. EP260327a: SVOM/VT optical upper limits
  67. SMA Detection of GRB 260310A / AT 2026fgk
  68. GRB 260307B: ATCA Radio Upper Limits
  69. EP260327a: WINTER J-band upper limit
  70. EP260327a: COLIBRÍ optical upper limits
  71. EP260327a: Gemini-North optical upper limits
  72. EP260324a: GROWTH-India Telescope optical observation
  73. EP260327a: Global MASTER-Net observations report
  74. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  75. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  76. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  77. IPN triangulation of GRB 260320A
  78. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  79. GRB 260326A: Fermi GBM Detection
  80. EP260321a: JinShan near-infrared observations
  81. EP260321a: Upper limits from a neutrino search with IceCube
  82. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  83. IPN triangulation of GRB 260316B
  84. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  85. GRID detection of GRB 260320A
  86. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  87. EP260321a: Gemini-South confirmation of a supernova
  88. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  89. GRB 260310A: LBT optical observations
  90. EP260321A: Mondy optical observations
  91. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  92. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  93. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  94. Fermi GRB 260323A: Global MASTER-Net observations report
  95. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  96. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  97. GRB 260320A: Glowbug gamma-ray detection
  98. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  99. EP260321a: COLIBRÍ further optical observations and brightening
  100. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate

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