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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"

28066 results found.

  1. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  2. Fermi GRB 260421A: Global MASTER-Net observations report
  3. EP260321a: VLA radio follow-up
  4. GRB 260412A: LCOGT Optical Upper Limits
  5. EP260416a: Optical follow-up observations with Kinder
  6. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  7. GRB 260417A: SVOM/GRM observation
  8. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  9. Fermi trigger No 798275385: Global MASTER-Net observations report
  10. EP260417a: GROWTH-India Telescope optical upper limit
  11. Fermi GRB 260417B: Global MASTER-Net observations report
  12. EP260417b: GROWTH-India Telescope optical upper limit
  13. EP260416a: Ondrejov D50 optical detection
  14. EP260417a: Global MASTER-Net observations report
  15. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  16. EP260416a: GMG Optical Observation
  17. Fermi GRB 260417A: Global MASTER-Net observations report
  18. EP260416a: LCO observations confirm end of flaring phase
  19. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  20. EP260417a: TRT optical counterpart detection
  21. EP260417a: Einstein Probe detection of an X-ray transient
  22. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  23. EP260417b: Einstein Probe detection of a fast X-ray transient
  24. EP260416a: KAIT optical upper limit
  25. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  26. EP260416a: WFST optical observations and rebrightening
  27. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  28. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  29. GRB 260415B: Glowbug gamma-ray detection
  30. GRB 260411B: Glowbug gamma-ray detection
  31. EP260416a: COLIBRÍ optical counterpart candidate
  32. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  33. EP260416a: Global MASTER-Net observations report
  34. EP260416a: Einstein Probe detection of an X-ray transient
  35. GOTO26djh/AT2026jpw : MASTER OT observation
  36. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  37. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  38. GRB 260415B: NuSTAR detection of long prompt emission
  39. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  40. Fermi trigger No 797912738: Global MASTER-Net observations report
  41. GRB 260414A: Glowbug gamma-ray detection
  42. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  43. EP260321a: CMO SAI J,K observations
  44. Fermi GRB 260413A: Global MASTER-Net observations report
  45. GRB 260410A: Glowbug gamma-ray detection of a short burst
  46. Fermi GRB 260412A: Global MASTER-Net observations report
  47. GRB 260412A: Fermi GBM Observation
  48. GRB 260411B: Fermi-LAT detection
  49. GRB 260411B: COLIBRÍ optical observations
  50. GRB 260410B: Fermi GBM Observation
  51. GRB260411B: 3.6m DOT optical observation
  52. GRB 260411A: SVOM/GRM observation
  53. GRB 260411B: SVOM/GRM observation of a long burst
  54. GRB 260409A: Insight-HXMT/HE detection
  55. GRB 260411B: Fermi GBM Detection
  56. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  57. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  58. GRB 260410A: COLIBRÍ optical upper limit
  59. EP-WXT01709259790: Optical Upper limits with kinder observations
  60. GRB 260410A: Fermi GBM Observation
  61. GRB 260410B: SVOM/GRM detection of a short faint burst
  62. EP-WXT01709259790: Xinglong optical upper limit
  63. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  64. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  65. EP260409a: COLIBRÍ optical upper limits
  66. EP260409a: Global MASTER-Net observations report
  67. EP260409a: Einstein Probe detection of an X-ray transient
  68. EP260321a: VLA radio detection
  69. GRB 260407A: Glowbug gamma-ray detection
  70. GRB 260402A: SVOM/ECLAIRs refined analysis
  71. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  72. EP260402a / GRB 260402A: Mephisto optical upper limits
  73. EP-WXT01709259586: Xinglong optical upper limit
  74. EP260403a: Mephisto optical upper limits
  75. EP260402a/GRB 260402A: Xinglong optical upper limit
  76. EP260405a: GMOS-N optical upper limits
  77. EP260405a: Global MASTER-Net observations report
  78. EP260405a: Einstein Probe detection of a fast X-ray transient
  79. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  80. Fermi trigger No 797039833: Global MASTER-Net observations report
  81. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  82. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  83. The EP-WXT trigger 01709259586 is likely a flaring star
  84. GRB 260330B: SVOM/VT further optical observation
  85. EP260403a: LCO optical observations of the counterpart
  86. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  87. EP260403a: LCO optical counterpart detection
  88. EP260403a: COLIBRÍ optical counterpart candidate
  89. GRB 260330B: SVOM/VT optical candidate
  90. EP260403a: Einstein Probe detection of an X-ray transient
  91. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  92. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  93. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  94. GRB 260402C: NuSTAR detection of prompt emission
  95. GRB 260402C: AstroSat CZTI detection of a long burst
  96. EP260324A / AT 2026hir: COLIBRÍ optical observations
  97. GRB 260402A: WINTER J-band upper limit
  98. GRB260402A: GROWTH-India Telescope optical upper limit
  99. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  100. EP260402a/GRB 260402A: SVOM/C-GFT upper limit

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