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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"

32538 results found.

  1. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  2. EP260507a: REM optical/NIR observations
  3. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  4. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  5. EP260507a: COLIBRÍ optical observations
  6. EP260507a: SVOM/VT optical observations
  7. EP260507a: NOT optical observations
  8. EP260507a: further Liverpool Telescope observations
  9. EP260507a: Liverpool Telescope optical upper limits
  10. EP260507a: GOTO optical counterpart detection
  11. EP260507a: TRT optical counterpart detection
  12. EP260507a: Kinder optical counterpart candidate
  13. EP260507a: LCO optical counterpart
  14. GRB 260504B: AstroSat CZTI detection
  15. GRB 260504B: SVOM/ECLAIRs refined analysis
  16. EP260502a is likely a flaring star
  17. Fermi GRB 260506A: Global MASTER-Net observations report
  18. GRB 260503A: GECAM-B observation of a burst
  19. GRB 260430B: Glowbug gamma-ray detection
  20. GRB 260504B: SVOM/VT optical upper limits
  21. GRB 260421B: radio observation with the VLA
  22. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  23. Konus-Wind detection of GRB 260504B (short/hard)
  24. GRB 260504B: GECAM-B detection
  25. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  26. GRB 260504B: SVOM/GRM spectral analysis
  27. GRB 260504B: SVOM/MXT refined analysis and potential detection
  28. GRB 260504B: EP-FXT upper limit
  29. GRB 260502A: SVOM/GRM observation of a short GRB
  30. GRB 260503A: SVOM/GRM observation of a GRB
  31. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  32. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  33. GRB 260504B: REM optical/NIR observations
  34. IPN triangulation of GRB 260429A
  35. IPN triangulation of GRB 260428A
  36. GRB 260504B: AST3-2 i-band upper limit
  37. GRB 260504B: LCO z-band upper limit
  38. SVOM GRB 260504B: MASTER-OAFA optical observations
  39. Fermi GRB 260504A: Global MASTER-Net observations report
  40. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  41. GRB 260502A: GECAM-B observation of a short burst
  42. IPN triangulation of a bright burst from SGR 1E1841-045
  43. GRB 260429B / EP260429a: EP-FXT follow-up observation
  44. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  45. GRB 260429B / EP260429a: AstroSat CZTI detection
  46. EP260502a: BOOTES-7: early optical upper limit
  47. EP260502a: Las Cumbres upper limit
  48. GRB 260429A: SVOM/GRM observation of a short burst
  49. EP260429a: Global MASTER-Net observations report
  50. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  51. GRB 260424B: AstroSat CZTI detection
  52. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  53. EP260429a: LCO optical upper limits
  54. EP260430a: LCO optical upper limits
  55. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  56. Fermi GRB 260429A: Global MASTER-Net observations report
  57. EP260430a: Global MASTER-Net observations report
  58. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  59. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  60. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  61. GRB 260428A: AstroSat CZTI detection
  62. Fermi GRB 260428A: Global MASTER-Net observations report
  63. EP260416a: Mondy and Terskol optical upper limits
  64. GRB 260424B: Glowbug gamma-ray detection of a short burst
  65. GRB 260424B: COLIBRÍ optical upper limit
  66. Konus-Wind detection of GRB 260424B
  67. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  68. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  69. IPN triangulation of GRB 260424B (short)
  70. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  71. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  72. GRB 260401A: cubesat Avion detection
  73. EP260321a: Upper limits from ATCA radio observations
  74. GRB 260421B: Kilonova-Catcher optical afterglow detection
  75. GRB 260421B: Insight-HXMT/HE detection
  76. The EP-WXT trigger 01709258652: Mondy optical observations
  77. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  78. EP260416a: Mondy optical observations
  79. GRB 260421B: SVOM/ECLAIRs refined analysis
  80. GRB 260421B: 3.6m DOT optical observation
  81. EP260416a: ZTSh R band observations
  82. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  83. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  84. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  85. GRB 260419A: AstroSat CZTI detection
  86. GRB 260421B: SVOM/GRM observation
  87. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  88. GRB 260421B: EP-FXT follow-up observation
  89. GOTO26djh/AT2026jpw: ATCA radio detection
  90. GRB 260421B: J-band upper limit with WINTER
  91. GRB 260421B: LCO optical counterpart detection
  92. GRB 260421B: Fermi GBM Observation
  93. GRB 260421A: AstroSat CZTI detection
  94. GOTO26djh/AT2026jpw: radio detection at 15GHz
  95. GRB 260412A: SVOM/ECLAIRs refined analysis
  96. GRB 260421B: SVOM/VT optical observations
  97. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  98. GRB 260310A: Late-time Chandra X-ray Detection
  99. GRB 260418A: Insight-HXMT/HE detection
  100. EP260416a: 1.3m DFOT optical observation

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