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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').
Advanced Search

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"
  1. GRB 260417B: Fermi GBM Final Real-time Localization
  2. GRB 260417A: AstroSat CZTI detection
  3. IPN triangulation of GRB 260411B
  4. EP260416a: LCO observations confirm end of flaring phase
  5. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  6. EP260417a: TRT optical counterpart detection
  7. EP260417a: Einstein Probe detection of an X-ray transient
  8. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  9. EP260417b: Einstein Probe detection of a fast X-ray transient
  10. EP-WXT trigger 01709259586: KAIT optical observations
  11. EP260416a: KAIT optical upper limit
  12. GRB 260414A: Insight-HXMT/HE detection
  13. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  14. EP260416a: WFST optical observations and rebrightening
  15. GRB 260417A: Fermi GBM Final Real-time Localization
  16. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  17. EP260416a: SVOM/VT optical observation
  18. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  19. GRB 260415B: Glowbug gamma-ray detection
  20. GRB 260411B: Glowbug gamma-ray detection
  21. GRB 260415A: Insight-HXMT/HE detection
  22. EP260416a: COLIBRÍ optical counterpart candidate
  23. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  24. EP260416a: Global MASTER-Net observations report
  25. EP260416a: Einstein Probe detection of an X-ray transient
  26. GOTO26djh/AT2026jpw : MASTER OT observation
  27. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  28. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  29. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  30. GRB 260415B: NuSTAR detection of long prompt emission
  31. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  32. GRB 260415B: Fermi GBM Final Localization
  33. GRB 260415A: Fermi GBM Final Real-time Localization
  34. Fermi trigger No 797912738: Global MASTER-Net observations report
  35. GRB 260414A: Glowbug gamma-ray detection
  36. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  37. EP260321a: CMO SAI J,K observations
  38. GRB 260412A: Insight-HXMT/HE detection
  39. GRB 260414A: Fermi GBM Final Real-time Localization
  40. The EP-WXT trigger 01709260122 is likely a flaring star
  41. Fermi GRB 260413A: Global MASTER-Net observations report
  42. GRB 260410A: Glowbug gamma-ray detection of a short burst
  43. GRB 260413A: Fermi GBM Final Real-time Localization
  44. GRB 260410B: Insight-HXMT/HE detection
  45. GRB 260410A: Insight-HXMT/HE detection
  46. Konus-Wind detection of GRB 260410A (short/hard)
  47. GRB 260411B: GECAM-B observation of a long burst
  48. EP260321a: SVOM/VT optical observations and color changes around peak
  49. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  50. The EP-WXT trigger 01709260010 is likely a flaring star
  51. GRB 260412A: GECAM-B observation of a long burst
  52. Fermi GRB 260412A: Global MASTER-Net observations report
  53. GRB 260412A: Fermi GBM Observation
  54. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  55. GRB 260411B: Fermi-LAT detection
  56. GRB 260412A: SVOM detection of a long burst
  57. GRB 260412A: Fermi GBM Final Real-time Localization
  58. GRB 260411B: COLIBRÍ optical observations
  59. GRB 260410B: Fermi GBM Observation
  60. GRB 260411B: Ondrejov D50 optical afterglow detection
  61. GRB260411B: 3.6m DOT optical observation
  62. GRB 260411A: SVOM/GRM observation
  63. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  64. GRB 260411B: SVOM/GRM observation of a long burst
  65. GRB 260409A: Insight-HXMT/HE detection
  66. GRB 260411B: Fermi GBM Detection
  67. GRB 260411B: GOTO optical counterpart candidate
  68. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  69. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  70. GRB 260411B: Fermi GBM Final Real-time Localization
  71. GRB 260411A: Fermi GBM Final Real-time Localization
  72. GRB 260410A: COLIBRÍ optical upper limit
  73. EP-WXT01709259790: Optical Upper limits with kinder observations
  74. GRB 260410A: Fermi GBM Observation
  75. GRB 260410B: SVOM/GRM detection of a short faint burst
  76. The EP-WXT trigger 01709259790 is likely a flaring star
  77. GRB 260410B: Fermi GBM Final Real-time Localization
  78. EP-WXT01709259790: Xinglong optical upper limit
  79. GRB 260410A: Fermi-LAT detection
  80. GRB 260410A: Fermi GBM Final Real-time Localization
  81. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  82. EP260321a: Chandra X-ray Non-detection
  83. GRB 260409A: Fermi GBM Final Real-time Localization
  84. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  85. The EP-WXT trigger 01709259773 is likely a flaring star
  86. GRB 260407A: GECAM-A detection
  87. GRB 260407A: Insight-HXMT/HE detection
  88. EP260409a: SVOM/VT optical upper limits
  89. EP260409a: COLIBRÍ optical upper limits
  90. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  91. EP260409a: Global MASTER-Net observations report
  92. EP260409a: Einstein Probe detection of an X-ray transient
  93. EP260321a: VLA radio detection
  94. GRB 260404A: Fermi GBM Final Localization
  95. GRB 260407A: Glowbug gamma-ray detection
  96. GRB 260402A: SVOM/ECLAIRs refined analysis
  97. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  98. GRB 260310A / AT2026fgk: X-ray rebrightening
  99. EP260402a / GRB 260402A: Mephisto optical upper limits
  100. EP-WXT01709259586: Xinglong optical upper limit

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