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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.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

32505 results found.

  1. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  2. EP260417a: TRT optical counterpart detection
  3. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  4. EP-WXT trigger 01709259586: KAIT optical observations
  5. EP260416a: KAIT optical upper limit
  6. GRB 260414A: Insight-HXMT/HE detection
  7. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  8. EP260416a: WFST optical observations and rebrightening
  9. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  10. EP260416a: SVOM/VT optical observation
  11. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  12. GRB 260415B: Glowbug gamma-ray detection
  13. GRB 260411B: Glowbug gamma-ray detection
  14. GRB 260415A: Insight-HXMT/HE detection
  15. EP260416a: COLIBRÍ optical counterpart candidate
  16. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  17. EP260416a: Global MASTER-Net observations report
  18. GOTO26djh/AT2026jpw : MASTER OT observation
  19. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  20. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  21. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  22. GRB 260415B: NuSTAR detection of long prompt emission
  23. GRB 260414A: Glowbug gamma-ray detection
  24. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  25. EP260321a: CMO SAI J,K observations
  26. GRB 260412A: Insight-HXMT/HE detection
  27. Fermi GRB 260413A: Global MASTER-Net observations report
  28. GRB 260410A: Glowbug gamma-ray detection of a short burst
  29. GRB 260410B: Insight-HXMT/HE detection
  30. GRB 260410A: Insight-HXMT/HE detection
  31. Konus-Wind detection of GRB 260410A (short/hard)
  32. GRB 260411B: GECAM-B observation of a long burst
  33. EP260321a: SVOM/VT optical observations and color changes around peak
  34. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  35. GRB 260412A: GECAM-B observation of a long burst
  36. Fermi GRB 260412A: Global MASTER-Net observations report
  37. GRB 260412A: Fermi GBM Observation
  38. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  39. GRB 260411B: Fermi-LAT detection
  40. GRB 260412A: SVOM detection of a long burst
  41. GRB 260411B: COLIBRÍ optical observations
  42. GRB 260410B: Fermi GBM Observation
  43. GRB 260411B: Ondrejov D50 optical afterglow detection
  44. GRB260411B: 3.6m DOT optical observation
  45. GRB 260411A: SVOM/GRM observation
  46. GRB 260411B: SVOM/GRM observation of a long burst
  47. GRB 260409A: Insight-HXMT/HE detection
  48. GRB 260411B: Fermi GBM Detection
  49. GRB 260411B: GOTO optical counterpart candidate
  50. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  51. GRB 260410A: COLIBRÍ optical upper limit
  52. EP-WXT01709259790: Optical Upper limits with kinder observations
  53. GRB 260410A: Fermi GBM Observation
  54. GRB 260410B: SVOM/GRM detection of a short faint burst
  55. GRB 260410A: Fermi-LAT detection
  56. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  57. EP260321a: Chandra X-ray Non-detection
  58. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  59. GRB 260407A: GECAM-A detection
  60. GRB 260407A: Insight-HXMT/HE detection
  61. EP260409a: SVOM/VT optical upper limits
  62. EP260409a: COLIBRÍ optical upper limits
  63. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  64. EP260409a: Global MASTER-Net observations report
  65. EP260321a: VLA radio detection
  66. GRB 260407A: Glowbug gamma-ray detection
  67. GRB 260402A: SVOM/ECLAIRs refined analysis
  68. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  69. GRB 260310A / AT2026fgk: X-ray rebrightening
  70. EP260402a / GRB 260402A: Mephisto optical upper limits
  71. EP-WXT01709259586: Xinglong optical upper limit
  72. EP260403a: Mephisto optical upper limits
  73. EP260402a/GRB 260402A: Xinglong optical upper limit
  74. EP260321a: Upper limits from VLA radio observations
  75. GRID detection of GRB 260401A
  76. EP260321a: uGMRT observations
  77. EP260405a: GMOS-N optical upper limits
  78. EP260405a: SVOM/VT optical upper limits
  79. EP260405a: Global MASTER-Net observations report
  80. EP260405a: Einstein Probe detection of a fast X-ray transient
  81. GRB 260403A: GECAM-B observation of a long burst
  82. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  83. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  84. GRB 260330B: SVOM/VT further optical observation
  85. GRB 260330B: SVOM/ECLAIRs refined analysis
  86. EP260403a: LCO optical observations of the counterpart
  87. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  88. EP260403a: LCO optical counterpart detection
  89. EP260403a: COLIBRÍ optical counterpart candidate
  90. GRB 260330B: SVOM/VT optical candidate
  91. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  92. GRB 260403A: AstroSat CZTI detection
  93. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  94. GRB 260402B: GECAM-B observation
  95. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  96. GRB 260402C: NuSTAR detection of prompt emission
  97. EP260324A / AT 2026hir: COLIBRÍ optical observations
  98. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  99. GRB 260402A: WINTER J-band upper limit
  100. GRB260402A: GROWTH-India Telescope optical upper limit

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