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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').
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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"

32544 results found.

  1. GRB 260509A: KAIT optical observations
  2. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  3. GRB 260509A: SVOM/VT optical candidate with VHF data
  4. GRB 260509A: LCO optical counterpart detection
  5. GRB 260509A: GOTO optical counterpart candidate
  6. GRB 260509A: SVOM detection of a burst
  7. GRB 260506B: AstroSat CZTI detection
  8. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  9. EP260507a: REM optical/NIR observations
  10. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  11. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  12. EP260507a: COLIBRÍ optical observations
  13. EP260507a: SVOM/VT optical observations
  14. EP260507a: NOT optical observations
  15. EP260507a: further Liverpool Telescope observations
  16. EP260507a: Liverpool Telescope optical upper limits
  17. EP260507a: GOTO optical counterpart detection
  18. EP260507a: TRT optical counterpart detection
  19. EP260507a: Kinder optical counterpart candidate
  20. EP260507a: LCO optical counterpart
  21. GRB 260504B: AstroSat CZTI detection
  22. GRB 260504B: SVOM/ECLAIRs refined analysis
  23. EP260502a is likely a flaring star
  24. Fermi GRB 260506A: Global MASTER-Net observations report
  25. GRB 260503A: GECAM-B observation of a burst
  26. GRB 260430B: Glowbug gamma-ray detection
  27. GRB 260504B: SVOM/VT optical upper limits
  28. GRB 260421B: radio observation with the VLA
  29. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  30. Konus-Wind detection of GRB 260504B (short/hard)
  31. GRB 260504B: GECAM-B detection
  32. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  33. GRB 260504B: SVOM/GRM spectral analysis
  34. GRB 260504B: SVOM/MXT refined analysis and potential detection
  35. GRB 260504B: EP-FXT upper limit
  36. GRB 260502A: SVOM/GRM observation of a short GRB
  37. GRB 260503A: SVOM/GRM observation of a GRB
  38. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  39. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  40. GRB 260504B: REM optical/NIR observations
  41. IPN triangulation of GRB 260429A
  42. IPN triangulation of GRB 260428A
  43. GRB 260504B: AST3-2 i-band upper limit
  44. GRB 260504B: LCO z-band upper limit
  45. SVOM GRB 260504B: MASTER-OAFA optical observations
  46. Fermi GRB 260504A: Global MASTER-Net observations report
  47. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  48. GRB 260502A: GECAM-B observation of a short burst
  49. IPN triangulation of a bright burst from SGR 1E1841-045
  50. GRB 260429B / EP260429a: EP-FXT follow-up observation
  51. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  52. GRB 260429B / EP260429a: AstroSat CZTI detection
  53. EP260502a: BOOTES-7: early optical upper limit
  54. EP260502a: Las Cumbres upper limit
  55. GRB 260429A: SVOM/GRM observation of a short burst
  56. EP260429a: Global MASTER-Net observations report
  57. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  58. GRB 260424B: AstroSat CZTI detection
  59. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  60. EP260429a: LCO optical upper limits
  61. EP260430a: LCO optical upper limits
  62. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  63. Fermi GRB 260429A: Global MASTER-Net observations report
  64. EP260430a: Global MASTER-Net observations report
  65. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  66. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  67. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  68. GRB 260428A: AstroSat CZTI detection
  69. Fermi GRB 260428A: Global MASTER-Net observations report
  70. EP260416a: Mondy and Terskol optical upper limits
  71. GRB 260424B: Glowbug gamma-ray detection of a short burst
  72. GRB 260424B: COLIBRÍ optical upper limit
  73. Konus-Wind detection of GRB 260424B
  74. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  75. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  76. IPN triangulation of GRB 260424B (short)
  77. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  78. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  79. GRB 260401A: cubesat Avion detection
  80. EP260321a: Upper limits from ATCA radio observations
  81. GRB 260421B: Kilonova-Catcher optical afterglow detection
  82. GRB 260421B: Insight-HXMT/HE detection
  83. The EP-WXT trigger 01709258652: Mondy optical observations
  84. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  85. EP260416a: Mondy optical observations
  86. GRB 260421B: SVOM/ECLAIRs refined analysis
  87. GRB 260421B: 3.6m DOT optical observation
  88. EP260416a: ZTSh R band observations
  89. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  90. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  91. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  92. GRB 260419A: AstroSat CZTI detection
  93. GRB 260421B: SVOM/GRM observation
  94. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  95. GRB 260421B: EP-FXT follow-up observation
  96. GOTO26djh/AT2026jpw: ATCA radio detection
  97. GRB 260421B: J-band upper limit with WINTER
  98. GRB 260421B: LCO optical counterpart detection
  99. GRB 260421B: Fermi GBM Observation
  100. GRB 260421A: AstroSat CZTI detection

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