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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"

32486 results found.

  1. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  2. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  3. GRB 260415B: NuSTAR detection of long prompt emission
  4. GRB 260414A: Glowbug gamma-ray detection
  5. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  6. EP260321a: CMO SAI J,K observations
  7. GRB 260412A: Insight-HXMT/HE detection
  8. Fermi GRB 260413A: Global MASTER-Net observations report
  9. GRB 260410A: Glowbug gamma-ray detection of a short burst
  10. GRB 260410B: Insight-HXMT/HE detection
  11. GRB 260410A: Insight-HXMT/HE detection
  12. Konus-Wind detection of GRB 260410A (short/hard)
  13. GRB 260411B: GECAM-B observation of a long burst
  14. EP260321a: SVOM/VT optical observations and color changes around peak
  15. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  16. GRB 260412A: GECAM-B observation of a long burst
  17. Fermi GRB 260412A: Global MASTER-Net observations report
  18. GRB 260412A: Fermi GBM Observation
  19. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  20. GRB 260411B: Fermi-LAT detection
  21. GRB 260412A: SVOM detection of a long burst
  22. GRB 260411B: COLIBRÍ optical observations
  23. GRB 260410B: Fermi GBM Observation
  24. GRB 260411B: Ondrejov D50 optical afterglow detection
  25. GRB260411B: 3.6m DOT optical observation
  26. GRB 260411A: SVOM/GRM observation
  27. GRB 260411B: SVOM/GRM observation of a long burst
  28. GRB 260409A: Insight-HXMT/HE detection
  29. GRB 260411B: Fermi GBM Detection
  30. GRB 260411B: GOTO optical counterpart candidate
  31. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  32. GRB 260410A: COLIBRÍ optical upper limit
  33. EP-WXT01709259790: Optical Upper limits with kinder observations
  34. GRB 260410A: Fermi GBM Observation
  35. GRB 260410B: SVOM/GRM detection of a short faint burst
  36. GRB 260410A: Fermi-LAT detection
  37. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  38. EP260321a: Chandra X-ray Non-detection
  39. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  40. GRB 260407A: GECAM-A detection
  41. GRB 260407A: Insight-HXMT/HE detection
  42. EP260409a: SVOM/VT optical upper limits
  43. EP260409a: COLIBRÍ optical upper limits
  44. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  45. EP260409a: Global MASTER-Net observations report
  46. EP260321a: VLA radio detection
  47. GRB 260407A: Glowbug gamma-ray detection
  48. GRB 260402A: SVOM/ECLAIRs refined analysis
  49. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  50. GRB 260310A / AT2026fgk: X-ray rebrightening
  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. EP260321a: Upper limits from VLA radio observations
  56. GRID detection of GRB 260401A
  57. EP260321a: uGMRT observations
  58. EP260405a: GMOS-N optical upper limits
  59. EP260405a: SVOM/VT optical upper limits
  60. EP260405a: Global MASTER-Net observations report
  61. EP260405a: Einstein Probe detection of a fast X-ray transient
  62. GRB 260403A: GECAM-B observation of a long burst
  63. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  64. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  65. GRB 260330B: SVOM/VT further optical observation
  66. GRB 260330B: SVOM/ECLAIRs refined analysis
  67. EP260403a: LCO optical observations of the counterpart
  68. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  69. EP260403a: LCO optical counterpart detection
  70. EP260403a: COLIBRÍ optical counterpart candidate
  71. GRB 260330B: SVOM/VT optical candidate
  72. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  73. GRB 260403A: AstroSat CZTI detection
  74. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  75. GRB 260402B: GECAM-B observation
  76. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  77. GRB 260402C: NuSTAR detection of prompt emission
  78. EP260324A / AT 2026hir: COLIBRÍ optical observations
  79. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  80. GRB 260402A: WINTER J-band upper limit
  81. GRB260402A: GROWTH-India Telescope optical upper limit
  82. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  83. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  84. GRB 260401A: SVOM/GRM observation
  85. GRB 260401A: GECAM-B observation
  86. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  87. GRB 260402A: Kilonova-Catcher optical upper limit
  88. GRB 260402A: MASTER optical observations
  89. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  90. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  91. Fermi GRB 260401A: Global MASTER-Net observations report
  92. GRB 260401A: Fermi GBM Observation
  93. GRB 260401A: NuSTAR detection of prompt emission
  94. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  95. GRB 260401A: MAXI/GSC detection
  96. EP260329b: Mondy and Assy-Turgen optical upper limits
  97. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  98. EP260321a :Xinglong optical observations
  99. EP260327a: Xinglong optical upper limit
  100. EP260329b: GOTO detection of optical counterpart

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