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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"

32514 results found.

  1. GRB 260504B: GECAM-B detection
  2. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  3. GRB 260504B: SVOM/GRM spectral analysis
  4. GRB 260504B: SVOM/MXT refined analysis and potential detection
  5. GRB 260504B: EP-FXT upper limit
  6. GRB 260502A: SVOM/GRM observation of a short GRB
  7. GRB 260503A: SVOM/GRM observation of a GRB
  8. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  9. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  10. GRB 260504B: REM optical/NIR observations
  11. IPN triangulation of GRB 260429A
  12. IPN triangulation of GRB 260428A
  13. GRB 260504B: AST3-2 i-band upper limit
  14. GRB 260504B: LCO z-band upper limit
  15. SVOM GRB 260504B: MASTER-OAFA optical observations
  16. Fermi GRB 260504A: Global MASTER-Net observations report
  17. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  18. GRB 260502A: GECAM-B observation of a short burst
  19. IPN triangulation of a bright burst from SGR 1E1841-045
  20. GRB 260429B / EP260429a: EP-FXT follow-up observation
  21. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  22. GRB 260429B / EP260429a: AstroSat CZTI detection
  23. EP260502a: BOOTES-7: early optical upper limit
  24. EP260502a: Las Cumbres upper limit
  25. GRB 260429A: SVOM/GRM observation of a short burst
  26. EP260429a: Global MASTER-Net observations report
  27. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  28. GRB 260424B: AstroSat CZTI detection
  29. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  30. EP260429a: LCO optical upper limits
  31. EP260430a: LCO optical upper limits
  32. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  33. Fermi GRB 260429A: Global MASTER-Net observations report
  34. EP260430a: Global MASTER-Net observations report
  35. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  36. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  37. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  38. GRB 260428A: AstroSat CZTI detection
  39. Fermi GRB 260428A: Global MASTER-Net observations report
  40. EP260416a: Mondy and Terskol optical upper limits
  41. GRB 260424B: Glowbug gamma-ray detection of a short burst
  42. GRB 260424B: COLIBRÍ optical upper limit
  43. Konus-Wind detection of GRB 260424B
  44. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  45. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  46. IPN triangulation of GRB 260424B (short)
  47. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  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. GRB 260421B: Insight-HXMT/HE detection
  53. The EP-WXT trigger 01709258652: Mondy optical observations
  54. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  55. EP260416a: Mondy optical observations
  56. GRB 260421B: SVOM/ECLAIRs refined analysis
  57. GRB 260421B: 3.6m DOT optical observation
  58. EP260416a: ZTSh R band observations
  59. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  60. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  61. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  62. GRB 260419A: AstroSat CZTI detection
  63. GRB 260421B: SVOM/GRM observation
  64. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  65. GRB 260421B: EP-FXT follow-up observation
  66. GOTO26djh/AT2026jpw: ATCA radio detection
  67. GRB 260421B: J-band upper limit with WINTER
  68. GRB 260421B: LCO optical counterpart detection
  69. GRB 260421B: Fermi GBM Observation
  70. GRB 260421A: AstroSat CZTI detection
  71. GOTO26djh/AT2026jpw: radio detection at 15GHz
  72. GRB 260412A: SVOM/ECLAIRs refined analysis
  73. GRB 260421B: SVOM/VT optical observations
  74. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  75. GRB 260310A: Late-time Chandra X-ray Detection
  76. GRB 260418A: Insight-HXMT/HE detection
  77. EP260416a: 1.3m DFOT optical observation
  78. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  79. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  80. Fermi GRB 260421C: Global MASTER-Net observations report
  81. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  82. Fermi GRB 260421B: Global MASTER-Net observations report
  83. GRB 260421B: BOOTES-7 early optical afterglow detection
  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. Fermi GRB 260421A: Global MASTER-Net observations report
  89. EP260321a: VLA radio follow-up
  90. GRB 260412A: LCOGT Optical Upper Limits
  91. EP260416a: Optical follow-up observations with Kinder
  92. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  93. EP-WXT trigger 01709260303: KAIT optical observations
  94. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  95. GRB 260417A: SVOM/GRM observation
  96. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  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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