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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 260418B: Fermi GBM Final Real-time Localization
  2. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  3. EP260417a: Global MASTER-Net observations report
  4. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  5. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  6. GRB 260418A: Fermi GBM Final Real-time Localization
  7. EP260416a: GMG Optical Observation
  8. Fermi GRB 260417A: Global MASTER-Net observations report
  9. Konus-Wind detection of GRB 260411B
  10. GRB 260417B: Fermi GBM Final Real-time Localization
  11. GRB 260417A: AstroSat CZTI detection
  12. IPN triangulation of GRB 260411B
  13. EP260416a: LCO observations confirm end of flaring phase
  14. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  15. EP260417a: TRT optical counterpart detection
  16. EP260417a: Einstein Probe detection of an X-ray transient
  17. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  18. EP260417b: Einstein Probe detection of a fast X-ray transient
  19. EP-WXT trigger 01709259586: KAIT optical observations
  20. EP260416a: KAIT optical upper limit
  21. GRB 260414A: Insight-HXMT/HE detection
  22. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  23. EP260416a: WFST optical observations and rebrightening
  24. GRB 260417A: Fermi GBM Final Real-time Localization
  25. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  26. EP260416a: SVOM/VT optical observation
  27. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  28. GRB 260415B: Glowbug gamma-ray detection
  29. GRB 260411B: Glowbug gamma-ray detection
  30. GRB 260415A: Insight-HXMT/HE 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: EP-FXT X-ray counterpart detection
  37. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  38. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  39. GRB 260415B: NuSTAR detection of long prompt emission
  40. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  41. GRB 260415B: Fermi GBM Final Localization
  42. GRB 260415A: Fermi GBM Final Real-time Localization
  43. Fermi trigger No 797912738: Global MASTER-Net observations report
  44. GRB 260414A: Glowbug gamma-ray detection
  45. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  46. EP260321a: CMO SAI J,K observations
  47. GRB 260412A: Insight-HXMT/HE detection
  48. GRB 260414A: Fermi GBM Final Real-time Localization
  49. The EP-WXT trigger 01709260122 is likely a flaring star
  50. Fermi GRB 260413A: Global MASTER-Net observations report
  51. GRB 260410A: Glowbug gamma-ray detection of a short burst
  52. GRB 260413A: Fermi GBM Final Real-time Localization
  53. GRB 260410B: Insight-HXMT/HE detection
  54. GRB 260410A: Insight-HXMT/HE detection
  55. Konus-Wind detection of GRB 260410A (short/hard)
  56. GRB 260411B: GECAM-B observation of a long burst
  57. EP260321a: SVOM/VT optical observations and color changes around peak
  58. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  59. The EP-WXT trigger 01709260010 is likely a flaring star
  60. GRB 260412A: GECAM-B observation of a long burst
  61. Fermi GRB 260412A: Global MASTER-Net observations report
  62. GRB 260412A: Fermi GBM Observation
  63. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  64. GRB 260411B: Fermi-LAT detection
  65. GRB 260412A: SVOM detection of a long burst
  66. GRB 260412A: Fermi GBM Final Real-time Localization
  67. GRB 260411B: COLIBRÍ optical observations
  68. GRB 260410B: Fermi GBM Observation
  69. GRB 260411B: Ondrejov D50 optical afterglow detection
  70. GRB260411B: 3.6m DOT optical observation
  71. GRB 260411A: SVOM/GRM observation
  72. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  73. GRB 260411B: SVOM/GRM observation of a long burst
  74. GRB 260409A: Insight-HXMT/HE detection
  75. GRB 260411B: Fermi GBM Detection
  76. GRB 260411B: GOTO optical counterpart candidate
  77. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  78. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  79. GRB 260411B: Fermi GBM Final Real-time Localization
  80. GRB 260411A: Fermi GBM Final Real-time Localization
  81. GRB 260410A: COLIBRÍ optical upper limit
  82. EP-WXT01709259790: Optical Upper limits with kinder observations
  83. GRB 260410A: Fermi GBM Observation
  84. GRB 260410B: SVOM/GRM detection of a short faint burst
  85. The EP-WXT trigger 01709259790 is likely a flaring star
  86. GRB 260410B: Fermi GBM Final Real-time Localization
  87. EP-WXT01709259790: Xinglong optical upper limit
  88. GRB 260410A: Fermi-LAT detection
  89. GRB 260410A: Fermi GBM Final Real-time Localization
  90. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  91. EP260321a: Chandra X-ray Non-detection
  92. GRB 260409A: Fermi GBM Final Real-time Localization
  93. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  94. The EP-WXT trigger 01709259773 is likely a flaring star
  95. GRB 260407A: GECAM-A detection
  96. GRB 260407A: Insight-HXMT/HE detection
  97. EP260409a: SVOM/VT optical upper limits
  98. EP260409a: COLIBRÍ optical upper limits
  99. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  100. EP260409a: Global MASTER-Net observations report

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