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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"

20378 results found.

  1. EP260321a: VLA radio follow-up
  2. GRB 260412A: LCOGT Optical Upper Limits
  3. EP260416a: Optical follow-up observations with Kinder
  4. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  5. GRB 260417A: SVOM/GRM observation
  6. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  7. EP260417a: GROWTH-India Telescope optical upper limit
  8. EP260417b: GROWTH-India Telescope optical upper limit
  9. EP260416a: Ondrejov D50 optical detection
  10. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  11. EP260416a: GMG Optical Observation
  12. EP260416a: LCO observations confirm end of flaring phase
  13. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  14. EP260417a: TRT optical counterpart detection
  15. EP260417a: Einstein Probe detection of an X-ray transient
  16. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  17. EP260417b: Einstein Probe detection of a fast X-ray transient
  18. EP260416a: KAIT optical upper limit
  19. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  20. EP260416a: WFST optical observations and rebrightening
  21. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  22. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  23. EP260416a: COLIBRÍ optical counterpart candidate
  24. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  25. EP260416a: Einstein Probe detection of an X-ray transient
  26. GOTO26djh/AT2026jpw : MASTER OT observation
  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. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  31. EP260321a: CMO SAI J,K observations
  32. GRB 260412A: Insight-HXMT/HE detection
  33. GRB 260412A: GECAM-B observation of a long burst
  34. GRB 260411B: Fermi-LAT detection
  35. GRB 260411B: COLIBRÍ optical observations
  36. GRB260411B: 3.6m DOT optical observation
  37. GRB 260411A: SVOM/GRM observation
  38. GRB 260411B: SVOM/GRM observation of a long burst
  39. GRB 260411B: Fermi GBM Detection
  40. GRB 260411B: GOTO optical counterpart candidate
  41. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  42. GRB 260410A: COLIBRÍ optical upper limit
  43. EP-WXT01709259790: Optical Upper limits with kinder observations
  44. EP-WXT01709259790: Xinglong optical upper limit
  45. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  46. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  47. EP260409a: COLIBRÍ optical upper limits
  48. EP260409a: Einstein Probe detection of an X-ray transient
  49. EP260321a: VLA radio detection
  50. GRB 260402A: SVOM/ECLAIRs refined analysis
  51. EP260402a / GRB 260402A: Mephisto optical upper limits
  52. EP-WXT01709259586: Xinglong optical upper limit
  53. EP260403a: Mephisto optical upper limits
  54. EP260402a/GRB 260402A: Xinglong optical upper limit
  55. GRID detection of GRB 260401A
  56. EP260405a: GMOS-N optical upper limits
  57. EP260405a: Einstein Probe detection of a fast X-ray transient
  58. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  59. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  60. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  61. GRB 260330B: SVOM/VT further optical observation
  62. GRB 260330B: SVOM/ECLAIRs refined analysis
  63. EP260403a: LCO optical observations of the counterpart
  64. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  65. EP260403a: LCO optical counterpart detection
  66. EP260403a: COLIBRÍ optical counterpart candidate
  67. GRB 260330B: SVOM/VT optical candidate
  68. EP260403a: Einstein Probe detection of an X-ray transient
  69. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  70. GRB 260403A: AstroSat CZTI detection
  71. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  72. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  73. GRB 260402C: AstroSat CZTI detection of a long burst
  74. EP260324A / AT 2026hir: COLIBRÍ optical observations
  75. GRB 260402A: WINTER J-band upper limit
  76. GRB260402A: GROWTH-India Telescope optical upper limit
  77. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  78. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  79. GRB 260401A: SVOM/GRM observation
  80. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  81. GRB 260402A: Kilonova-Catcher optical upper limit
  82. GRB 260402A: MASTER optical observations
  83. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  84. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  85. GRB 260402A: SVOM detection of a burst
  86. EP260329b: Mondy and Assy-Turgen optical upper limits
  87. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  88. EP260321a :Xinglong optical observations
  89. EP260327a: Xinglong optical upper limit
  90. GRB 260330B: SVOM/VT optical upper limits
  91. GRB 260321A: SVOM/ECLAIRs refined analysis
  92. EP260329b: J-band upper limits with WINTER
  93. EP260329a: J-band upper limit with WINTER
  94. GRB 260310A: VLA Multi-frequency Radio Observations
  95. GRB 260330B: LCO optical upper limits
  96. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  97. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  98. EP260329a: COLIBRÍ optical upper limit
  99. EP260329a: EP-FXT follow up observation
  100. EP260329a: NOT optical counterpart candidate

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