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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"

23417 results found.

  1. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  2. EP260417a: GROWTH-India Telescope optical upper limit
  3. EP260417b: GROWTH-India Telescope optical upper limit
  4. EP260416a: Ondrejov D50 optical detection
  5. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  6. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  7. EP260416a: GMG Optical Observation
  8. GRB 260417A: AstroSat CZTI detection
  9. IPN triangulation of GRB 260411B
  10. EP260416a: LCO observations confirm end of flaring phase
  11. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  12. EP260417a: TRT optical counterpart detection
  13. EP260417a: Einstein Probe detection of an X-ray transient
  14. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  15. EP260417b: Einstein Probe detection of a fast X-ray transient
  16. EP260416a: KAIT optical upper limit
  17. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  18. EP260416a: WFST optical observations and rebrightening
  19. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  20. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  21. GRB 260415B: Glowbug gamma-ray detection
  22. GRB 260411B: Glowbug gamma-ray detection
  23. GRB 260415A: Insight-HXMT/HE detection
  24. EP260416a: COLIBRÍ optical counterpart candidate
  25. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  26. EP260416a: Einstein Probe detection of an X-ray transient
  27. GOTO26djh/AT2026jpw : MASTER OT observation
  28. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  29. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  30. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  31. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  32. GRB 260414A: Glowbug gamma-ray detection
  33. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  34. EP260321a: CMO SAI J,K observations
  35. GRB 260410A: Glowbug gamma-ray detection of a short burst
  36. GRB 260412A: Fermi GBM Observation
  37. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  38. GRB 260411B: Fermi-LAT detection
  39. GRB 260411B: COLIBRÍ optical observations
  40. GRB260411B: 3.6m DOT optical observation
  41. GRB 260411A: SVOM/GRM observation
  42. GRB 260411B: SVOM/GRM observation of a long burst
  43. GRB 260409A: Insight-HXMT/HE detection
  44. GRB 260411B: Fermi GBM Detection
  45. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  46. GRB 260410A: COLIBRÍ optical upper limit
  47. EP-WXT01709259790: Optical Upper limits with kinder observations
  48. EP-WXT01709259790: Xinglong optical upper limit
  49. GRB 260410A: Fermi-LAT detection
  50. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  51. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  52. EP260409a: SVOM/VT optical upper limits
  53. EP260409a: COLIBRÍ optical upper limits
  54. EP260409a: Einstein Probe detection of an X-ray transient
  55. EP260321a: VLA radio detection
  56. GRB 260407A: Glowbug gamma-ray detection
  57. GRB 260402A: SVOM/ECLAIRs refined analysis
  58. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  59. GRB 260310A / AT2026fgk: X-ray rebrightening
  60. EP260402a / GRB 260402A: Mephisto optical upper limits
  61. EP-WXT01709259586: Xinglong optical upper limit
  62. EP260403a: Mephisto optical upper limits
  63. EP260402a/GRB 260402A: Xinglong optical upper limit
  64. EP260321a: Upper limits from VLA radio observations
  65. EP260405a: GMOS-N optical upper limits
  66. EP260405a: SVOM/VT optical upper limits
  67. EP260405a: Einstein Probe detection of a fast X-ray transient
  68. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  69. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  70. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  71. GRB 260330B: SVOM/VT further optical observation
  72. EP260403a: LCO optical observations of the counterpart
  73. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  74. EP260403a: LCO optical counterpart detection
  75. EP260403a: COLIBRÍ optical counterpart candidate
  76. GRB 260330B: SVOM/VT optical candidate
  77. EP260403a: Einstein Probe detection of an X-ray transient
  78. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  79. GRB 260403A: AstroSat CZTI detection
  80. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  81. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  82. GRB 260402C: AstroSat CZTI detection of a long burst
  83. EP260324A / AT 2026hir: COLIBRÍ optical observations
  84. GRB 260403A: Fermi GBM Final Real-time Localization
  85. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  86. GRB 260402A: WINTER J-band upper limit
  87. GRB260402A: GROWTH-India Telescope optical upper limit
  88. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  89. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  90. GRB 260401A: SVOM/GRM observation
  91. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  92. GRB 260402A: Kilonova-Catcher optical upper limit
  93. GRB 260402A: MASTER optical observations
  94. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  95. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  96. GRB 260402A: SVOM detection of a burst
  97. EP260329b: Mondy and Assy-Turgen optical upper limits
  98. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  99. EP260321a :Xinglong optical observations
  100. EP260327a: Xinglong optical upper limit

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