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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"

28048 results found.

  1. Fermi GRB 260510A: Global MASTER-Net observations report
  2. GRB 260509A: KAIT optical observations
  3. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  4. GRB 260509A: SVOM/VT optical candidate with VHF data
  5. GRB 260509A: LCO optical counterpart detection
  6. GRB 260509A: SVOM detection of a burst
  7. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  8. EP260507a: REM optical/NIR observations
  9. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  10. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  11. EP260507a: COLIBRÍ optical observations
  12. EP260507a: NOT optical observations
  13. EP260507a: further Liverpool Telescope observations
  14. EP260507a: Liverpool Telescope optical upper limits
  15. EP260507a: TRT optical counterpart detection
  16. EP260507a: Kinder optical counterpart candidate
  17. EP260507a: LCO optical counterpart
  18. EP260507a: Einstein Probe detection of an X-ray transient
  19. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  20. Fermi GRB 260506A: Global MASTER-Net observations report
  21. IceCube Alert 260505A: Global MASTER-Net observations report
  22. GRB 260430B: Glowbug gamma-ray detection
  23. GRB 260421B: radio observation with the VLA
  24. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  25. GRB 260430B: AstroSat CZTI detection of a long burst
  26. GRB 260502A: SVOM/GRM observation of a short GRB
  27. GRB 260503A: SVOM/GRM observation of a GRB
  28. Konus-Wind detection of GRB 260411C
  29. GRB 260504B: REM optical/NIR observations
  30. GRB 260504B: LCO z-band upper limit
  31. SVOM GRB 260504B: MASTER-OAFA optical observations
  32. GRB 260504B: SVOM detection of a short burst
  33. Fermi GRB 260504A: Global MASTER-Net observations report
  34. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  35. GRB 260429B / EP260429a: EP-FXT follow-up observation
  36. EP260502a: Einstein Probe detection of an X-ray transient
  37. GRB 260429A: SVOM/GRM observation of a short burst
  38. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  39. EP260429a: Global MASTER-Net observations report
  40. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  41. GRB 260424B: AstroSat CZTI detection
  42. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  43. EP260429a: LCO optical upper limits
  44. EP260430a: LCO optical upper limits
  45. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  46. GRB 260429A: Fermi GBM Detection
  47. Fermi GRB 260429A: Global MASTER-Net observations report
  48. EP260430a: Global MASTER-Net observations report
  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. Fermi GRB 260428A: Global MASTER-Net observations report
  54. EP260416a: Mondy and Terskol optical upper limits
  55. GRB 260424B: Glowbug gamma-ray detection of a short burst
  56. GRB 260424B: COLIBRÍ optical upper limit
  57. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  58. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  59. IceCube Alert 260425A: Global MASTER-Net observations report
  60. Fermi trigger No 798737427: Global MASTER-Net observations report
  61. GRB 260401A: cubesat Avion detection
  62. EP260321a: Upper limits from ATCA radio observations
  63. GRB 260421B: Kilonova-Catcher optical afterglow detection
  64. The EP-WXT trigger 01709258652: Mondy optical observations
  65. EP260416a: Mondy optical observations
  66. GRB 260421B: 3.6m DOT optical observation
  67. EP260416a: ZTSh R band observations
  68. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  69. GRB 260421B: SVOM/GRM observation
  70. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  71. GRB 260421B: EP-FXT follow-up observation
  72. GOTO26djh/AT2026jpw: ATCA radio detection
  73. GRB 260421B: J-band upper limit with WINTER
  74. GRB 260421B: LCO optical counterpart detection
  75. GRB 260421B: Fermi GBM Observation
  76. GOTO26djh/AT2026jpw: radio detection at 15GHz
  77. GRB 260421B: SVOM/VT optical observations
  78. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  79. GRB 260310A: Late-time Chandra X-ray Detection
  80. EP260416a: 1.3m DFOT optical observation
  81. Fermi GRB 260421C: Global MASTER-Net observations report
  82. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  83. Fermi GRB 260421B: Global MASTER-Net observations report
  84. GRB 260421B: LCO optical afterglow confirmation
  85. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  86. GRB 260421B: TRT optical counterpart detection
  87. GRB 260421B: SVOM detection of a long burst
  88. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  89. Fermi GRB 260421A: Global MASTER-Net observations report
  90. EP260321a: VLA radio follow-up
  91. GRB 260412A: LCOGT Optical Upper Limits
  92. EP260416a: Optical follow-up observations with Kinder
  93. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  94. GRB 260417A: SVOM/GRM observation
  95. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  96. Fermi trigger No 798275385: Global MASTER-Net observations report
  97. EP260417a: GROWTH-India Telescope optical upper limit
  98. Fermi GRB 260417B: Global MASTER-Net observations report
  99. EP260417b: GROWTH-India Telescope optical upper limit
  100. EP260416a: Ondrejov D50 optical detection

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