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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"

28055 results found.

  1. Fermi GBM Sub-Threshold Detection of GRB 260510B
  2. GRB 260510C: SVOM detection of a burst
  3. GRB 260510B: LCO optical upper limits
  4. EP260509a: Einstein Probe detection of an X-ray transient
  5. GRB 260509A: Liverpool Telescope optical observations
  6. GRB 260510B: SVOM detection of a burst
  7. GRB 260509A: LCO optical observations
  8. SVOM GRB 260509A: MASTER-OAFA optical observation
  9. Fermi GRB 260510A: Global MASTER-Net observations report
  10. GRB 260509A: KAIT optical observations
  11. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  12. GRB 260509A: SVOM/VT optical candidate with VHF data
  13. GRB 260509A: LCO optical counterpart detection
  14. GRB 260509A: SVOM detection of a burst
  15. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  16. EP260507a: REM optical/NIR observations
  17. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  18. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  19. EP260507a: COLIBRÍ optical observations
  20. EP260507a: NOT optical observations
  21. EP260507a: further Liverpool Telescope observations
  22. EP260507a: Liverpool Telescope optical upper limits
  23. EP260507a: TRT optical counterpart detection
  24. EP260507a: Kinder optical counterpart candidate
  25. EP260507a: LCO optical counterpart
  26. EP260507a: Einstein Probe detection of an X-ray transient
  27. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  28. Fermi GRB 260506A: Global MASTER-Net observations report
  29. IceCube Alert 260505A: Global MASTER-Net observations report
  30. GRB 260430B: Glowbug gamma-ray detection
  31. GRB 260421B: radio observation with the VLA
  32. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  33. GRB 260430B: AstroSat CZTI detection of a long burst
  34. GRB 260502A: SVOM/GRM observation of a short GRB
  35. GRB 260503A: SVOM/GRM observation of a GRB
  36. Konus-Wind detection of GRB 260411C
  37. GRB 260504B: REM optical/NIR observations
  38. GRB 260504B: LCO z-band upper limit
  39. SVOM GRB 260504B: MASTER-OAFA optical observations
  40. GRB 260504B: SVOM detection of a short burst
  41. Fermi GRB 260504A: Global MASTER-Net observations report
  42. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  43. GRB 260429B / EP260429a: EP-FXT follow-up observation
  44. EP260502a: Einstein Probe detection of an X-ray transient
  45. GRB 260429A: SVOM/GRM observation of a short burst
  46. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  47. EP260429a: Global MASTER-Net observations report
  48. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  49. GRB 260424B: AstroSat CZTI detection
  50. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  51. EP260429a: LCO optical upper limits
  52. EP260430a: LCO optical upper limits
  53. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  54. GRB 260429A: Fermi GBM Detection
  55. Fermi GRB 260429A: Global MASTER-Net observations report
  56. EP260430a: Global MASTER-Net observations report
  57. EP260430a: Einstein Probe detection of an X-ray transient
  58. EP260429a: EP-WXT detection of a fast X-ray transient
  59. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  60. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  61. Fermi GRB 260428A: Global MASTER-Net observations report
  62. EP260416a: Mondy and Terskol optical upper limits
  63. GRB 260424B: Glowbug gamma-ray detection of a short burst
  64. GRB 260424B: COLIBRÍ optical upper limit
  65. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  66. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  67. IceCube Alert 260425A: Global MASTER-Net observations report
  68. Fermi trigger No 798737427: Global MASTER-Net observations report
  69. GRB 260401A: cubesat Avion detection
  70. EP260321a: Upper limits from ATCA radio observations
  71. GRB 260421B: Kilonova-Catcher optical afterglow detection
  72. The EP-WXT trigger 01709258652: Mondy optical observations
  73. EP260416a: Mondy optical observations
  74. GRB 260421B: 3.6m DOT optical observation
  75. EP260416a: ZTSh R band observations
  76. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  77. GRB 260421B: SVOM/GRM observation
  78. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  79. GRB 260421B: EP-FXT follow-up observation
  80. GOTO26djh/AT2026jpw: ATCA radio detection
  81. GRB 260421B: J-band upper limit with WINTER
  82. GRB 260421B: LCO optical counterpart detection
  83. GRB 260421B: Fermi GBM Observation
  84. GOTO26djh/AT2026jpw: radio detection at 15GHz
  85. GRB 260421B: SVOM/VT optical observations
  86. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  87. GRB 260310A: Late-time Chandra X-ray Detection
  88. EP260416a: 1.3m DFOT optical observation
  89. Fermi GRB 260421C: Global MASTER-Net observations report
  90. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  91. Fermi GRB 260421B: Global MASTER-Net observations report
  92. GRB 260421B: LCO optical afterglow confirmation
  93. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  94. GRB 260421B: TRT optical counterpart detection
  95. GRB 260421B: SVOM detection of a long burst
  96. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  97. Fermi GRB 260421A: Global MASTER-Net observations report
  98. EP260321a: VLA radio follow-up
  99. GRB 260412A: LCOGT Optical Upper Limits
  100. EP260416a: Optical follow-up observations with Kinder

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