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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. The EP-WXT trigger 01709260314 is likely a flaring star
  2. EP260416a: Optical follow-up observations with Kinder
  3. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  4. EP-WXT trigger 01709260303: KAIT optical observations
  5. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  6. The EP-WXT trigger 01709260303 is likely a flaring star
  7. GRB 260417A: SVOM/GRM observation
  8. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  9. GRB 260419B: Fermi GBM Final Real-time Localization
  10. GRB 260419A: Fermi GBM Final Real-time Localization
  11. Fermi trigger No 798275385: Global MASTER-Net observations report
  12. EP260417a: GROWTH-India Telescope optical upper limit
  13. Fermi GRB 260417B: Global MASTER-Net observations report
  14. EP260417b: GROWTH-India Telescope optical upper limit
  15. EP260416a: Ondrejov D50 optical detection
  16. GRB 260418B: Fermi GBM Final Real-time Localization
  17. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  18. EP260417a: Global MASTER-Net observations report
  19. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  20. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  21. GRB 260418A: Fermi GBM Final Real-time Localization
  22. EP260416a: GMG Optical Observation
  23. Fermi GRB 260417A: Global MASTER-Net observations report
  24. Konus-Wind detection of GRB 260411B
  25. GRB 260417B: Fermi GBM Final Real-time Localization
  26. GRB 260417A: AstroSat CZTI detection
  27. IPN triangulation of GRB 260411B
  28. EP260416a: LCO observations confirm end of flaring phase
  29. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  30. EP260417a: TRT optical counterpart detection
  31. EP260417a: Einstein Probe detection of an X-ray transient
  32. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  33. EP260417b: Einstein Probe detection of a fast X-ray transient
  34. EP-WXT trigger 01709259586: KAIT optical observations
  35. EP260416a: KAIT optical upper limit
  36. GRB 260414A: Insight-HXMT/HE detection
  37. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  38. EP260416a: WFST optical observations and rebrightening
  39. GRB 260417A: Fermi GBM Final Real-time Localization
  40. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  41. EP260416a: SVOM/VT optical observation
  42. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  43. GRB 260415B: Glowbug gamma-ray detection
  44. GRB 260411B: Glowbug gamma-ray detection
  45. GRB 260415A: Insight-HXMT/HE detection
  46. EP260416a: COLIBRÍ optical counterpart candidate
  47. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  48. EP260416a: Global MASTER-Net observations report
  49. EP260416a: Einstein Probe detection of an X-ray transient
  50. GOTO26djh/AT2026jpw : MASTER OT observation
  51. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  52. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  53. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  54. GRB 260415B: NuSTAR detection of long prompt emission
  55. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  56. GRB 260415B: Fermi GBM Final Localization
  57. GRB 260415A: Fermi GBM Final Real-time Localization
  58. Fermi trigger No 797912738: Global MASTER-Net observations report
  59. GRB 260414A: Glowbug gamma-ray detection
  60. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  61. EP260321a: CMO SAI J,K observations
  62. GRB 260412A: Insight-HXMT/HE detection
  63. GRB 260414A: Fermi GBM Final Real-time Localization
  64. The EP-WXT trigger 01709260122 is likely a flaring star
  65. Fermi GRB 260413A: Global MASTER-Net observations report
  66. GRB 260410A: Glowbug gamma-ray detection of a short burst
  67. GRB 260413A: Fermi GBM Final Real-time Localization
  68. GRB 260410B: Insight-HXMT/HE detection
  69. GRB 260410A: Insight-HXMT/HE detection
  70. Konus-Wind detection of GRB 260410A (short/hard)
  71. GRB 260411B: GECAM-B observation of a long burst
  72. EP260321a: SVOM/VT optical observations and color changes around peak
  73. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  74. The EP-WXT trigger 01709260010 is likely a flaring star
  75. GRB 260412A: GECAM-B observation of a long burst
  76. Fermi GRB 260412A: Global MASTER-Net observations report
  77. GRB 260412A: Fermi GBM Observation
  78. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  79. GRB 260411B: Fermi-LAT detection
  80. GRB 260412A: SVOM detection of a long burst
  81. GRB 260412A: Fermi GBM Final Real-time Localization
  82. GRB 260411B: COLIBRÍ optical observations
  83. GRB 260410B: Fermi GBM Observation
  84. GRB 260411B: Ondrejov D50 optical afterglow detection
  85. GRB260411B: 3.6m DOT optical observation
  86. GRB 260411A: SVOM/GRM observation
  87. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  88. GRB 260411B: SVOM/GRM observation of a long burst
  89. GRB 260409A: Insight-HXMT/HE detection
  90. GRB 260411B: Fermi GBM Detection
  91. GRB 260411B: GOTO optical counterpart candidate
  92. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  93. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  94. GRB 260411B: Fermi GBM Final Real-time Localization
  95. GRB 260411A: Fermi GBM Final Real-time Localization
  96. GRB 260410A: COLIBRÍ optical upper limit
  97. EP-WXT01709259790: Optical Upper limits with kinder observations
  98. GRB 260410A: Fermi GBM Observation
  99. GRB 260410B: SVOM/GRM detection of a short faint burst
  100. The EP-WXT trigger 01709259790 is likely a flaring star

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