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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"

28045 results found.

  1. EP260416a: GMG Optical Observation
  2. Fermi GRB 260417A: Global MASTER-Net observations report
  3. EP260416a: LCO observations confirm end of flaring phase
  4. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  5. EP260417a: TRT optical counterpart detection
  6. EP260417a: Einstein Probe detection of an X-ray transient
  7. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  8. EP260417b: Einstein Probe detection of a fast X-ray transient
  9. EP260416a: KAIT optical upper limit
  10. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  11. EP260416a: WFST optical observations and rebrightening
  12. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  13. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  14. GRB 260415B: Glowbug gamma-ray detection
  15. GRB 260411B: Glowbug gamma-ray detection
  16. EP260416a: COLIBRÍ optical counterpart candidate
  17. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  18. EP260416a: Global MASTER-Net observations report
  19. EP260416a: Einstein Probe detection of an X-ray transient
  20. GOTO26djh/AT2026jpw : MASTER OT observation
  21. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  22. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  23. GRB 260415B: NuSTAR detection of long prompt emission
  24. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  25. Fermi trigger No 797912738: Global MASTER-Net observations report
  26. GRB 260414A: Glowbug gamma-ray detection
  27. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  28. EP260321a: CMO SAI J,K observations
  29. Fermi GRB 260413A: Global MASTER-Net observations report
  30. GRB 260410A: Glowbug gamma-ray detection of a short burst
  31. Fermi GRB 260412A: Global MASTER-Net observations report
  32. GRB 260412A: Fermi GBM Observation
  33. GRB 260411B: Fermi-LAT detection
  34. GRB 260411B: COLIBRÍ optical observations
  35. GRB 260410B: Fermi GBM Observation
  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 260409A: Insight-HXMT/HE detection
  40. GRB 260411B: Fermi GBM Detection
  41. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  42. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  43. GRB 260410A: COLIBRÍ optical upper limit
  44. EP-WXT01709259790: Optical Upper limits with kinder observations
  45. GRB 260410A: Fermi GBM Observation
  46. GRB 260410B: SVOM/GRM detection of a short faint burst
  47. EP-WXT01709259790: Xinglong optical upper limit
  48. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  49. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  50. EP260409a: COLIBRÍ optical upper limits
  51. EP260409a: Global MASTER-Net observations report
  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. EP260402a / GRB 260402A: Mephisto optical upper limits
  58. EP-WXT01709259586: Xinglong optical upper limit
  59. EP260403a: Mephisto optical upper limits
  60. EP260402a/GRB 260402A: Xinglong optical upper limit
  61. EP260405a: GMOS-N optical upper limits
  62. EP260405a: Global MASTER-Net observations report
  63. EP260405a: Einstein Probe detection of a fast X-ray transient
  64. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  65. Fermi trigger No 797039833: Global MASTER-Net observations report
  66. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  67. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  68. The EP-WXT trigger 01709259586 is likely a flaring star
  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. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  78. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  79. GRB 260402C: NuSTAR detection of prompt emission
  80. GRB 260402C: AstroSat CZTI detection of a long burst
  81. EP260324A / AT 2026hir: COLIBRÍ optical observations
  82. GRB 260402A: WINTER J-band upper limit
  83. GRB260402A: GROWTH-India Telescope optical upper limit
  84. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  85. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  86. GRB 260401A: SVOM/GRM observation
  87. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  88. GRB 260402A: Kilonova-Catcher optical upper limit
  89. GRB 260402A: MASTER optical observations
  90. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  91. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  92. GRB 260402A: SVOM detection of a burst
  93. Fermi GRB 260401A: Global MASTER-Net observations report
  94. GRB 260401A: Fermi GBM Observation
  95. GRB 260401A: NuSTAR detection of prompt emission
  96. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  97. GRB 260401A: MAXI/GSC detection
  98. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  99. GRB 260401A: Fermi GBM Final Real-time Localization
  100. EP260329b: Mondy and Assy-Turgen optical upper limits

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