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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"

19857 results found.

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

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