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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. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  2. GRB 260419B: Fermi GBM Final Real-time Localization
  3. GRB 260419A: Fermi GBM Final Real-time Localization
  4. Fermi trigger No 798275385: Global MASTER-Net observations report
  5. EP260417a: GROWTH-India Telescope optical upper limit
  6. Fermi GRB 260417B: Global MASTER-Net observations report
  7. EP260417b: GROWTH-India Telescope optical upper limit
  8. EP260416a: Ondrejov D50 optical detection
  9. GRB 260418B: Fermi GBM Final Real-time Localization
  10. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  11. EP260417a: Global MASTER-Net observations report
  12. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  13. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  14. GRB 260418A: Fermi GBM Final Real-time Localization
  15. EP260416a: GMG Optical Observation
  16. Fermi GRB 260417A: Global MASTER-Net observations report
  17. Konus-Wind detection of GRB 260411B
  18. GRB 260417B: Fermi GBM Final Real-time Localization
  19. GRB 260417A: AstroSat CZTI detection
  20. IPN triangulation of GRB 260411B
  21. EP260416a: LCO observations confirm end of flaring phase
  22. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  23. EP260417a: TRT optical counterpart detection
  24. EP260417a: Einstein Probe detection of an X-ray transient
  25. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  26. EP260417b: Einstein Probe detection of a fast X-ray transient
  27. EP-WXT trigger 01709259586: KAIT optical observations
  28. EP260416a: KAIT optical upper limit
  29. GRB 260414A: Insight-HXMT/HE detection
  30. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  31. EP260416a: WFST optical observations and rebrightening
  32. GRB 260417A: Fermi GBM Final Real-time Localization
  33. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  34. EP260416a: SVOM/VT optical observation
  35. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  36. GRB 260415B: Glowbug gamma-ray detection
  37. GRB 260411B: Glowbug gamma-ray detection
  38. GRB 260415A: Insight-HXMT/HE detection
  39. EP260416a: COLIBRÍ optical counterpart candidate
  40. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  41. EP260416a: Global MASTER-Net observations report
  42. EP260416a: Einstein Probe detection of an X-ray transient
  43. GOTO26djh/AT2026jpw : MASTER OT observation
  44. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  45. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  46. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  47. GRB 260415B: NuSTAR detection of long prompt emission
  48. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  49. GRB 260415B: Fermi GBM Final Localization
  50. GRB 260415A: Fermi GBM Final Real-time Localization
  51. Fermi trigger No 797912738: Global MASTER-Net observations report
  52. GRB 260414A: Glowbug gamma-ray detection
  53. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  54. EP260321a: CMO SAI J,K observations
  55. GRB 260412A: Insight-HXMT/HE detection
  56. GRB 260414A: Fermi GBM Final Real-time Localization
  57. The EP-WXT trigger 01709260122 is likely a flaring star
  58. Fermi GRB 260413A: Global MASTER-Net observations report
  59. GRB 260410A: Glowbug gamma-ray detection of a short burst
  60. GRB 260413A: Fermi GBM Final Real-time Localization
  61. GRB 260410B: Insight-HXMT/HE detection
  62. GRB 260410A: Insight-HXMT/HE detection
  63. Konus-Wind detection of GRB 260410A (short/hard)
  64. GRB 260411B: GECAM-B observation of a long burst
  65. EP260321a: SVOM/VT optical observations and color changes around peak
  66. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  67. The EP-WXT trigger 01709260010 is likely a flaring star
  68. GRB 260412A: GECAM-B observation of a long burst
  69. Fermi GRB 260412A: Global MASTER-Net observations report
  70. GRB 260412A: Fermi GBM Observation
  71. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  72. GRB 260411B: Fermi-LAT detection
  73. GRB 260412A: SVOM detection of a long burst
  74. GRB 260412A: Fermi GBM Final Real-time Localization
  75. GRB 260411B: COLIBRÍ optical observations
  76. GRB 260410B: Fermi GBM Observation
  77. GRB 260411B: Ondrejov D50 optical afterglow detection
  78. GRB260411B: 3.6m DOT optical observation
  79. GRB 260411A: SVOM/GRM observation
  80. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  81. GRB 260411B: SVOM/GRM observation of a long burst
  82. GRB 260409A: Insight-HXMT/HE detection
  83. GRB 260411B: Fermi GBM Detection
  84. GRB 260411B: GOTO optical counterpart candidate
  85. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  86. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  87. GRB 260411B: Fermi GBM Final Real-time Localization
  88. GRB 260411A: Fermi GBM Final Real-time Localization
  89. GRB 260410A: COLIBRÍ optical upper limit
  90. EP-WXT01709259790: Optical Upper limits with kinder observations
  91. GRB 260410A: Fermi GBM Observation
  92. GRB 260410B: SVOM/GRM detection of a short faint burst
  93. The EP-WXT trigger 01709259790 is likely a flaring star
  94. GRB 260410B: Fermi GBM Final Real-time Localization
  95. EP-WXT01709259790: Xinglong optical upper limit
  96. GRB 260410A: Fermi-LAT detection
  97. GRB 260410A: Fermi GBM Final Real-time Localization
  98. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  99. EP260321a: Chandra X-ray Non-detection
  100. GRB 260409A: Fermi GBM Final Real-time Localization

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