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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

32686 results found.

  1. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  2. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  3. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  4. GRB 260415B: NuSTAR detection of long prompt emission
  5. GRB 260414A: Glowbug gamma-ray detection
  6. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  7. EP260321a: CMO SAI J,K observations
  8. GRB 260412A: Insight-HXMT/HE detection
  9. Fermi GRB 260413A: Global MASTER-Net observations report
  10. GRB 260410A: Glowbug gamma-ray detection of a short burst
  11. GRB 260410B: Insight-HXMT/HE detection
  12. GRB 260410A: Insight-HXMT/HE detection
  13. Konus-Wind detection of GRB 260410A (short/hard)
  14. GRB 260411B: GECAM-B observation of a long burst
  15. EP260321a: SVOM/VT optical observations and color changes around peak
  16. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  17. GRB 260412A: GECAM-B observation of a long burst
  18. Fermi GRB 260412A: Global MASTER-Net observations report
  19. GRB 260412A: Fermi GBM Observation
  20. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  21. GRB 260411B: Fermi-LAT detection
  22. GRB 260412A: SVOM detection of a long burst
  23. GRB 260411B: COLIBRÍ optical observations
  24. GRB 260410B: Fermi GBM Observation
  25. GRB 260411B: Ondrejov D50 optical afterglow detection
  26. GRB260411B: 3.6m DOT optical observation
  27. GRB 260411A: SVOM/GRM observation
  28. GRB 260411B: SVOM/GRM observation of a long burst
  29. GRB 260409A: Insight-HXMT/HE detection
  30. GRB 260411B: Fermi GBM Detection
  31. GRB 260411B: GOTO optical counterpart candidate
  32. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  33. GRB 260410A: COLIBRÍ optical upper limit
  34. EP-WXT01709259790: Optical Upper limits with kinder observations
  35. GRB 260410A: Fermi GBM Observation
  36. GRB 260410B: SVOM/GRM detection of a short faint burst
  37. GRB 260410A: Fermi-LAT detection
  38. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  39. EP260321a: Chandra X-ray Non-detection
  40. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  41. GRB 260407A: GECAM-A detection
  42. GRB 260407A: Insight-HXMT/HE detection
  43. EP260409a: SVOM/VT optical upper limits
  44. EP260409a: COLIBRÍ optical upper limits
  45. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  46. EP260409a: Global MASTER-Net observations report
  47. EP260321a: VLA radio detection
  48. GRB 260407A: Glowbug gamma-ray detection
  49. GRB 260402A: SVOM/ECLAIRs refined analysis
  50. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  51. GRB 260310A / AT2026fgk: X-ray rebrightening
  52. EP260402a / GRB 260402A: Mephisto optical upper limits
  53. EP-WXT01709259586: Xinglong optical upper limit
  54. EP260403a: Mephisto optical upper limits
  55. EP260402a/GRB 260402A: Xinglong optical upper limit
  56. EP260321a: Upper limits from VLA radio observations
  57. GRID detection of GRB 260401A
  58. EP260321a: uGMRT observations
  59. EP260405a: GMOS-N optical upper limits
  60. EP260405a: SVOM/VT optical upper limits
  61. EP260405a: Global MASTER-Net observations report
  62. EP260405a: Einstein Probe detection of a fast X-ray transient
  63. GRB 260403A: GECAM-B observation of a long burst
  64. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  65. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  66. GRB 260330B: SVOM/VT further optical observation
  67. GRB 260330B: SVOM/ECLAIRs refined analysis
  68. EP260403a: LCO optical observations of the counterpart
  69. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  70. EP260403a: LCO optical counterpart detection
  71. EP260403a: COLIBRÍ optical counterpart candidate
  72. GRB 260330B: SVOM/VT optical candidate
  73. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  74. GRB 260403A: AstroSat CZTI detection
  75. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  76. GRB 260402B: GECAM-B observation
  77. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  78. GRB 260402C: NuSTAR detection of prompt emission
  79. EP260324A / AT 2026hir: COLIBRÍ optical observations
  80. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  81. GRB 260402A: WINTER J-band upper limit
  82. GRB260402A: GROWTH-India Telescope optical upper limit
  83. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  84. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  85. GRB 260401A: SVOM/GRM observation
  86. GRB 260401A: GECAM-B 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. Fermi GRB 260401A: Global MASTER-Net observations report
  93. GRB 260401A: Fermi GBM Observation
  94. GRB 260401A: NuSTAR detection of prompt emission
  95. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  96. GRB 260401A: MAXI/GSC detection
  97. EP260329b: Mondy and Assy-Turgen optical upper limits
  98. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  99. EP260321a :Xinglong optical observations
  100. EP260327a: Xinglong optical upper limit

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