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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').
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"

26499 results found.

  1. EP260507a: LCO optical counterpart
  2. EP260507a: Einstein Probe detection of an X-ray transient
  3. GRB 260504B: SVOM/ECLAIRs refined analysis
  4. EP260502a is likely a flaring star
  5. GRB 260430B: Glowbug gamma-ray detection
  6. GRB 260504B: SVOM/VT optical upper limits
  7. GRB 260421B: radio observation with the VLA
  8. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  9. Konus-Wind detection of GRB 260504B (short/hard)
  10. GRB 260504B: GECAM-B detection
  11. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  12. GRB 260504B: SVOM/GRM spectral analysis
  13. GRB 260430B: AstroSat CZTI detection of a long burst
  14. GRB 260504B: EP-FXT upper limit
  15. GRB 260502A: SVOM/GRM observation of a short GRB
  16. GRB 260503A: SVOM/GRM observation of a GRB
  17. Konus-Wind detection of GRB 260415C
  18. GRB 260504B: REM optical/NIR observations
  19. GRB 260504B: AST3-2 i-band upper limit
  20. GRB 260504B: LCO z-band upper limit
  21. SVOM GRB 260504B: MASTER-OAFA optical observations
  22. GRB 260504B: SVOM detection of a short burst
  23. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  24. IPN triangulation of a bright burst from SGR 1E1841-045
  25. The EP-WXT trigger 01709261576 is likely a flaring star
  26. GRB 260429B / EP260429a: EP-FXT follow-up observation
  27. EP260502a: BOOTES-7: early optical upper limit
  28. EP260502a: Einstein Probe detection of an X-ray transient
  29. GRB 260429A: SVOM/GRM observation of a short burst
  30. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  31. EP260429a: Global MASTER-Net observations report
  32. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  33. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  34. EP260429a: LCO optical upper limits
  35. EP260430a: LCO optical upper limits
  36. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  37. GRB 260429A: Fermi GBM Detection
  38. EP260430a: Einstein Probe detection of an X-ray transient
  39. EP260429a: EP-WXT detection of a fast X-ray transient
  40. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  41. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  42. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  43. EP260416a: Mondy and Terskol optical upper limits
  44. GRB 260424B: Glowbug gamma-ray detection of a short burst
  45. GRB 260424B: COLIBRÍ optical upper limit
  46. Konus-Wind detection of GRB 260424B
  47. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  48. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  49. GRB 260401A: cubesat Avion detection
  50. EP260321a: Upper limits from ATCA radio observations
  51. GRB 260421B: Kilonova-Catcher optical afterglow detection
  52. EP260416a: Mondy optical observations
  53. GRB 260421B: SVOM/ECLAIRs refined analysis
  54. GRB 260421B: 3.6m DOT optical observation
  55. EP260416a: ZTSh R band observations
  56. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  57. GRB 260419A: AstroSat CZTI detection
  58. GRB 260421B: SVOM/GRM observation
  59. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  60. The EP-WXT trigger 01709260362 is likely a flaring star
  61. GOTO26djh/AT2026jpw: ATCA radio detection
  62. GRB 260421B: J-band upper limit with WINTER
  63. GRB 260421B: LCO optical counterpart detection
  64. GRB 260421B: Fermi GBM Observation
  65. GOTO26djh/AT2026jpw: radio detection at 15GHz
  66. GRB 260412A: SVOM/ECLAIRs refined analysis
  67. GRB 260421B: SVOM/VT optical observations
  68. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  69. GRB 260310A: Late-time Chandra X-ray Detection
  70. EP260416a: 1.3m DFOT optical observation
  71. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  72. GRB 260421B: LCO optical afterglow confirmation
  73. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  74. GRB 260421B: TRT optical counterpart detection
  75. GRB 260421B: SVOM detection of a long burst
  76. EP260321a: VLA radio follow-up
  77. GRB 260412A: LCOGT Optical Upper Limits
  78. The EP-WXT trigger 01709260314 is likely a flaring star
  79. EP260416a: Optical follow-up observations with Kinder
  80. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  81. The EP-WXT trigger 01709260303 is likely a flaring star
  82. GRB 260417A: SVOM/GRM observation
  83. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  84. EP260417a: GROWTH-India Telescope optical upper limit
  85. EP260417b: GROWTH-India Telescope optical upper limit
  86. EP260416a: Ondrejov D50 optical detection
  87. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  88. EP260416a: GMG Optical Observation
  89. EP260416a: LCO observations confirm end of flaring phase
  90. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  91. EP260417a: TRT optical counterpart detection
  92. EP260417a: Einstein Probe detection of an X-ray transient
  93. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  94. EP260417b: Einstein Probe detection of a fast X-ray transient
  95. EP260416a: KAIT optical upper limit
  96. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  97. EP260416a: WFST optical observations and rebrightening
  98. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  99. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  100. GRB 260415B: Glowbug gamma-ray detection

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