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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"

23415 results found.

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

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