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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"

19548 results found.

  1. EP260416a: ZTSh R band observations
  2. GRB 260421B: SVOM/GRM observation
  3. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  4. GOTO26djh/AT2026jpw: ATCA radio detection
  5. GRB 260421B: J-band upper limit with WINTER
  6. GRB 260421B: LCO optical counterpart detection
  7. GRB 260421A: AstroSat CZTI detection
  8. GRB 260421B: SVOM/VT optical observations
  9. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  10. GRB 260310A: Late-time Chandra X-ray Detection
  11. EP260416a: 1.3m DFOT optical observation
  12. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  13. GRB 260421B: LCO optical afterglow confirmation
  14. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  15. GRB 260421B: TRT optical counterpart detection
  16. GRB 260421B: SVOM detection of a long burst
  17. EP260321a: VLA radio follow-up
  18. GRB 260412A: LCOGT Optical Upper Limits
  19. EP260416a: Optical follow-up observations with Kinder
  20. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  21. GRB 260417A: SVOM/GRM observation
  22. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  23. EP260417a: GROWTH-India Telescope optical upper limit
  24. EP260417b: GROWTH-India Telescope optical upper limit
  25. EP260416a: Ondrejov D50 optical detection
  26. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  27. EP260416a: GMG Optical Observation
  28. EP260416a: LCO observations confirm end of flaring phase
  29. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  30. EP260417a: TRT optical counterpart detection
  31. EP260417a: Einstein Probe detection of an X-ray transient
  32. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  33. EP260417b: Einstein Probe detection of a fast X-ray transient
  34. EP260416a: KAIT optical upper limit
  35. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  36. EP260416a: WFST optical observations and rebrightening
  37. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  38. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  39. EP260416a: COLIBRÍ optical counterpart candidate
  40. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  41. EP260416a: Einstein Probe detection of an X-ray transient
  42. GOTO26djh/AT2026jpw : MASTER OT observation
  43. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  44. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  45. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  46. EP260321a: CMO SAI J,K observations
  47. GRB 260411B: Fermi-LAT detection
  48. GRB 260412A: SVOM detection of a long burst
  49. GRB 260411B: COLIBRÍ optical observations
  50. GRB260411B: 3.6m DOT optical observation
  51. GRB 260411A: SVOM/GRM observation
  52. GRB 260411B: SVOM/GRM observation of a long burst
  53. GRB 260411B: GOTO optical counterpart candidate
  54. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  55. GRB 260410A: COLIBRÍ optical upper limit
  56. EP-WXT01709259790: Optical Upper limits with kinder observations
  57. EP-WXT01709259790: Xinglong optical upper limit
  58. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  59. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  60. EP260409a: COLIBRÍ optical upper limits
  61. EP260409a: Einstein Probe detection of an X-ray transient
  62. EP260321a: VLA radio detection
  63. GRB 260402A: SVOM/ECLAIRs refined analysis
  64. EP260402a / GRB 260402A: Mephisto optical upper limits
  65. EP-WXT01709259586: Xinglong optical upper limit
  66. EP260403a: Mephisto optical upper limits
  67. EP260402a/GRB 260402A: Xinglong optical upper limit
  68. EP260405a: GMOS-N optical upper limits
  69. EP260405a: Einstein Probe detection of a fast X-ray transient
  70. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  71. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  72. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  73. The EP-WXT trigger 01709259586 is likely a flaring star
  74. GRB 260330B: SVOM/VT further optical observation
  75. EP260403a: LCO optical observations of the counterpart
  76. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  77. EP260403a: LCO optical counterpart detection
  78. EP260403a: COLIBRÍ optical counterpart candidate
  79. GRB 260330B: SVOM/VT optical candidate
  80. EP260403a: Einstein Probe detection of an X-ray transient
  81. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  82. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  83. EP260324A / AT 2026hir: COLIBRÍ optical observations
  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. GRB 260330B: SVOM/VT optical upper limits
  100. GRB 260321A: SVOM/ECLAIRs refined analysis

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