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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. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  2. The EP-WXT trigger 01709260303 is likely a flaring star
  3. GRB 260417A: SVOM/GRM observation
  4. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  5. GRB 260419B: Fermi GBM Final Real-time Localization
  6. GRB 260419A: Fermi GBM Final Real-time Localization
  7. Fermi trigger No 798275385: Global MASTER-Net observations report
  8. EP260417a: GROWTH-India Telescope optical upper limit
  9. Fermi GRB 260417B: Global MASTER-Net observations report
  10. EP260417b: GROWTH-India Telescope optical upper limit
  11. EP260416a: Ondrejov D50 optical detection
  12. GRB 260418B: Fermi GBM Final Real-time Localization
  13. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  14. EP260417a: Global MASTER-Net observations report
  15. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  16. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  17. GRB 260418A: Fermi GBM Final Real-time Localization
  18. EP260416a: GMG Optical Observation
  19. Fermi GRB 260417A: Global MASTER-Net observations report
  20. Konus-Wind detection of GRB 260411B
  21. GRB 260417B: Fermi GBM Final Real-time Localization
  22. GRB 260417A: AstroSat CZTI detection
  23. IPN triangulation of GRB 260411B
  24. EP260416a: LCO observations confirm end of flaring phase
  25. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  26. EP260417a: TRT optical counterpart detection
  27. EP260417a: Einstein Probe detection of an X-ray transient
  28. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  29. EP260417b: Einstein Probe detection of a fast X-ray transient
  30. EP-WXT trigger 01709259586: KAIT optical observations
  31. EP260416a: KAIT optical upper limit
  32. GRB 260414A: Insight-HXMT/HE detection
  33. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  34. EP260416a: WFST optical observations and rebrightening
  35. GRB 260417A: Fermi GBM Final Real-time Localization
  36. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  37. EP260416a: SVOM/VT optical observation
  38. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  39. GRB 260415B: Glowbug gamma-ray detection
  40. GRB 260411B: Glowbug gamma-ray detection
  41. GRB 260415A: Insight-HXMT/HE detection
  42. EP260416a: COLIBRÍ optical counterpart candidate
  43. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  44. EP260416a: Global MASTER-Net observations report
  45. EP260416a: Einstein Probe detection of an X-ray transient
  46. GOTO26djh/AT2026jpw : MASTER OT observation
  47. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  48. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  49. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  50. GRB 260415B: NuSTAR detection of long prompt emission
  51. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  52. GRB 260415B: Fermi GBM Final Localization
  53. GRB 260415A: Fermi GBM Final Real-time Localization
  54. Fermi trigger No 797912738: Global MASTER-Net observations report
  55. GRB 260414A: Glowbug gamma-ray detection
  56. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  57. EP260321a: CMO SAI J,K observations
  58. GRB 260412A: Insight-HXMT/HE detection
  59. GRB 260414A: Fermi GBM Final Real-time Localization
  60. The EP-WXT trigger 01709260122 is likely a flaring star
  61. Fermi GRB 260413A: Global MASTER-Net observations report
  62. GRB 260410A: Glowbug gamma-ray detection of a short burst
  63. GRB 260413A: Fermi GBM Final Real-time Localization
  64. GRB 260410B: Insight-HXMT/HE detection
  65. GRB 260410A: Insight-HXMT/HE detection
  66. Konus-Wind detection of GRB 260410A (short/hard)
  67. GRB 260411B: GECAM-B observation of a long burst
  68. EP260321a: SVOM/VT optical observations and color changes around peak
  69. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  70. The EP-WXT trigger 01709260010 is likely a flaring star
  71. GRB 260412A: GECAM-B observation of a long burst
  72. Fermi GRB 260412A: Global MASTER-Net observations report
  73. GRB 260412A: Fermi GBM Observation
  74. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  75. GRB 260411B: Fermi-LAT detection
  76. GRB 260412A: SVOM detection of a long burst
  77. GRB 260412A: Fermi GBM Final Real-time Localization
  78. GRB 260411B: COLIBRÍ optical observations
  79. GRB 260410B: Fermi GBM Observation
  80. GRB 260411B: Ondrejov D50 optical afterglow detection
  81. GRB260411B: 3.6m DOT optical observation
  82. GRB 260411A: SVOM/GRM observation
  83. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  84. GRB 260411B: SVOM/GRM observation of a long burst
  85. GRB 260409A: Insight-HXMT/HE detection
  86. GRB 260411B: Fermi GBM Detection
  87. GRB 260411B: GOTO optical counterpart candidate
  88. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  89. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  90. GRB 260411B: Fermi GBM Final Real-time Localization
  91. GRB 260411A: Fermi GBM Final Real-time Localization
  92. GRB 260410A: COLIBRÍ optical upper limit
  93. EP-WXT01709259790: Optical Upper limits with kinder observations
  94. GRB 260410A: Fermi GBM Observation
  95. GRB 260410B: SVOM/GRM detection of a short faint burst
  96. The EP-WXT trigger 01709259790 is likely a flaring star
  97. GRB 260410B: Fermi GBM Final Real-time Localization
  98. EP-WXT01709259790: Xinglong optical upper limit
  99. GRB 260410A: Fermi-LAT detection
  100. GRB 260410A: Fermi GBM Final Real-time Localization

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