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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"

39236 results found.

  1. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  2. GRB 260504C: SVOM/GRM observation of short GRB
  3. GRB 260504B: SVOM/GRM spectral analysis
  4. GRB 260430B: AstroSat CZTI detection of a long burst
  5. GRB 260504B: SVOM/MXT refined analysis and potential detection
  6. GRB 260504B: EP-FXT upper limit
  7. GRB 260502A: SVOM/GRM observation of a short GRB
  8. GRB 260503A: SVOM/GRM observation of a GRB
  9. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  10. Konus-Wind detection of GRB 260415C
  11. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  12. Konus-Wind detection of GRB 260411C
  13. GRB 260504B: REM optical/NIR observations
  14. IPN triangulation of GRB 260429A
  15. IPN triangulation of GRB 260428A
  16. GRB 260504B: AST3-2 i-band upper limit
  17. GRB 260504B: LCO z-band upper limit
  18. SVOM GRB 260504B: MASTER-OAFA optical observations
  19. GRB 260504B: SVOM detection of a short burst
  20. Fermi GRB 260504A: Global MASTER-Net observations report
  21. GRB 260504A: Fermi GBM Final Real-time Localization
  22. GRB 260503A: Fermi GBM Final Real-time Localization
  23. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  24. GRB 260502A: GECAM-B observation of a short burst
  25. GRB 260502A: Fermi GBM Final Localization
  26. GRB 260429B / EP260429a: EP-FXT follow-up observation
  27. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  28. GRB 260429B / EP260429a: AstroSat CZTI detection
  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. GRB 260424B: AstroSat CZTI detection
  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. Fermi GRB 260429A: Global MASTER-Net observations report
  39. EP260430a: Global MASTER-Net observations report
  40. GRB 260429A: Fermi GBM Final Real-time Localization
  41. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  42. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  43. GRB 260428A: AstroSat CZTI detection
  44. Fermi GRB 260428A: Global MASTER-Net observations report
  45. EP260416a: Mondy and Terskol optical upper limits
  46. GRB 260424B: Glowbug gamma-ray detection of a short burst
  47. GRB 260424B: COLIBRÍ optical upper limit
  48. Konus-Wind detection of GRB 260424B
  49. GRB 260428A: Fermi GBM Final Real-time Localization
  50. GRB 260424C: Fermi GBM Final Localization
  51. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  52. IPN triangulation of GRB 260424B (short)
  53. GRB 260424B: SVOM/GRM detection of a short burst
  54. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  55. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  56. IceCube Alert 260425A: Global MASTER-Net observations report
  57. Fermi trigger No 798737427: Global MASTER-Net observations report
  58. GRB 260401A: cubesat Avion detection
  59. GRB 260424A: AstroSat CZTI detection of a long burst
  60. GRB 260421B: Kilonova-Catcher optical afterglow detection
  61. GRB 260421B: Insight-HXMT/HE detection
  62. The EP-WXT trigger 01709258652: Mondy optical observations
  63. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  64. EP260416a: Mondy optical observations
  65. GRB 260421B: SVOM/ECLAIRs refined analysis
  66. GRB 260421B: 3.6m DOT optical observation
  67. EP260416a: ZTSh R band observations
  68. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  69. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  70. GRB 260419A: AstroSat CZTI detection
  71. GRB 260421B: SVOM/GRM observation
  72. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  73. GRB 260421B: EP-FXT follow-up observation
  74. GRB 260421B: J-band upper limit with WINTER
  75. GRB 260421B: LCO optical counterpart detection
  76. GRB 260421B: Fermi GBM Observation
  77. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  78. GRB 260421A: AstroSat CZTI detection
  79. GRB 260412A: SVOM/ECLAIRs refined analysis
  80. GRB 260421B: SVOM/VT optical observations
  81. GRB 260310A: Late-time Chandra X-ray Detection
  82. GRB 260418A: Insight-HXMT/HE detection
  83. EP260416a: 1.3m DFOT optical observation
  84. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  85. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  86. Fermi GRB 260421C: Global MASTER-Net observations report
  87. GRB 260421C: Fermi GBM Final Real-time Localization
  88. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  89. Fermi GRB 260421B: Global MASTER-Net observations report
  90. GRB 260421B: BOOTES-7 early optical afterglow detection
  91. GRB 260421B: LCO optical afterglow confirmation
  92. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  93. GRB 260421B: TRT optical counterpart detection
  94. GRB 260421B: SVOM detection of a long burst
  95. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  96. GRB 260421B: Fermi GBM Final Real-time Localization
  97. Fermi GRB 260421A: Global MASTER-Net observations report
  98. GRB 260421A: Fermi GBM Final Real-time Localization
  99. GRB 260412A: LCOGT Optical Upper Limits
  100. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient

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