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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"

19862 results found.

  1. GRB 260510B: LCO optical upper limits
  2. EP260509a: Einstein Probe detection of an X-ray transient
  3. GRB 260509A: Liverpool Telescope optical observations
  4. GRB 260510B: SVOM detection of a burst
  5. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  6. GRB 260509A: LCO optical observations
  7. SVOM GRB 260509A: MASTER-OAFA optical observation
  8. GRB 260509A: KAIT optical observations
  9. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  10. GRB 260509A: SVOM/VT optical candidate with VHF data
  11. GRB 260509A: LCO optical counterpart detection
  12. GRB 260509A: SVOM detection of a burst
  13. GRB 260506B: AstroSat CZTI detection
  14. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  15. EP260507a: REM optical/NIR observations
  16. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  17. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  18. EP260507a: COLIBRÍ optical observations
  19. EP260507a: NOT optical observations
  20. EP260507a: further Liverpool Telescope observations
  21. EP260507a: Liverpool Telescope optical upper limits
  22. EP260507a: TRT optical counterpart detection
  23. EP260507a: Kinder optical counterpart candidate
  24. EP260507a: LCO optical counterpart
  25. EP260507a: Einstein Probe detection of an X-ray transient
  26. GRB 260504B: SVOM/ECLAIRs refined analysis
  27. EP260502a is likely a flaring star
  28. GRB 260503A: GECAM-B observation of a burst
  29. GRB 260421B: radio observation with the VLA
  30. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  31. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  32. GRB 260430B: AstroSat CZTI detection of a long burst
  33. GRB 260502A: SVOM/GRM observation of a short GRB
  34. GRB 260503A: SVOM/GRM observation of a GRB
  35. GRB 260504B: REM optical/NIR observations
  36. GRB 260504B: LCO z-band upper limit
  37. SVOM GRB 260504B: MASTER-OAFA optical observations
  38. GRB 260504B: SVOM detection of a short burst
  39. GRB 260504A: Fermi GBM Final Real-time Localization
  40. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  41. EP260502a: Einstein Probe detection of an X-ray transient
  42. GRB 260429A: SVOM/GRM observation of a short burst
  43. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  44. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  45. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  46. EP260429a: LCO optical upper limits
  47. EP260430a: LCO optical upper limits
  48. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  49. EP260430a: Einstein Probe detection of an X-ray transient
  50. EP260429a: EP-WXT detection of a fast X-ray transient
  51. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  52. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  53. GRB 260428A: AstroSat CZTI detection
  54. EP260416a: Mondy and Terskol optical upper limits
  55. GRB 260424B: COLIBRÍ optical upper limit
  56. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  57. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  58. GRB 260401A: cubesat Avion detection
  59. EP260321a: Upper limits from ATCA radio observations
  60. GRB 260421B: Kilonova-Catcher optical afterglow detection
  61. EP260416a: Mondy optical observations
  62. GRB 260421B: SVOM/ECLAIRs refined analysis
  63. GRB 260421B: 3.6m DOT optical observation
  64. EP260416a: ZTSh R band observations
  65. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  66. GRB 260421B: SVOM/GRM observation
  67. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  68. GOTO26djh/AT2026jpw: ATCA radio detection
  69. GRB 260421B: J-band upper limit with WINTER
  70. GRB 260421B: LCO optical counterpart detection
  71. GRB 260412A: SVOM/ECLAIRs refined analysis
  72. GRB 260421B: SVOM/VT optical observations
  73. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  74. GRB 260310A: Late-time Chandra X-ray Detection
  75. EP260416a: 1.3m DFOT optical observation
  76. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  77. GRB 260421B: LCO optical afterglow confirmation
  78. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  79. GRB 260421B: TRT optical counterpart detection
  80. GRB 260421B: SVOM detection of a long burst
  81. EP260321a: VLA radio follow-up
  82. GRB 260412A: LCOGT Optical Upper Limits
  83. EP260416a: Optical follow-up observations with Kinder
  84. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  85. GRB 260417A: SVOM/GRM observation
  86. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  87. EP260417a: GROWTH-India Telescope optical upper limit
  88. EP260417b: GROWTH-India Telescope optical upper limit
  89. EP260416a: Ondrejov D50 optical detection
  90. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  91. EP260416a: GMG Optical Observation
  92. EP260416a: LCO observations confirm end of flaring phase
  93. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  94. EP260417a: TRT optical counterpart detection
  95. EP260417a: Einstein Probe detection of an X-ray transient
  96. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  97. EP260417b: Einstein Probe detection of a fast X-ray transient
  98. EP260416a: KAIT optical upper limit
  99. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  100. EP260416a: WFST optical observations and rebrightening

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