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

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