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

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