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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"

20359 results found.

  1. EP260416a: WFST optical observations and rebrightening
  2. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  3. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  4. EP260416a: COLIBRÍ optical counterpart candidate
  5. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  6. EP260416a: Einstein Probe detection of an X-ray transient
  7. GOTO26djh/AT2026jpw : MASTER OT observation
  8. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  9. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  10. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  11. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  12. EP260321a: CMO SAI J,K observations
  13. GRB 260412A: Insight-HXMT/HE detection
  14. GRB 260412A: GECAM-B observation of a long burst
  15. GRB 260411B: Fermi-LAT detection
  16. GRB 260411B: COLIBRÍ optical observations
  17. GRB260411B: 3.6m DOT optical observation
  18. GRB 260411A: SVOM/GRM observation
  19. GRB 260411B: SVOM/GRM observation of a long burst
  20. GRB 260411B: Fermi GBM Detection
  21. GRB 260411B: GOTO optical counterpart candidate
  22. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  23. GRB 260410A: COLIBRÍ optical upper limit
  24. EP-WXT01709259790: Optical Upper limits with kinder observations
  25. EP-WXT01709259790: Xinglong optical upper limit
  26. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  27. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  28. EP260409a: COLIBRÍ optical upper limits
  29. EP260409a: Einstein Probe detection of an X-ray transient
  30. EP260321a: VLA radio detection
  31. GRB 260402A: SVOM/ECLAIRs refined analysis
  32. EP260402a / GRB 260402A: Mephisto optical upper limits
  33. EP-WXT01709259586: Xinglong optical upper limit
  34. EP260403a: Mephisto optical upper limits
  35. EP260402a/GRB 260402A: Xinglong optical upper limit
  36. GRID detection of GRB 260401A
  37. EP260405a: GMOS-N optical upper limits
  38. EP260405a: Einstein Probe detection of a fast X-ray transient
  39. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  40. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  41. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  42. GRB 260330B: SVOM/VT further optical observation
  43. GRB 260330B: SVOM/ECLAIRs refined analysis
  44. EP260403a: LCO optical observations of the counterpart
  45. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  46. EP260403a: LCO optical counterpart detection
  47. EP260403a: COLIBRÍ optical counterpart candidate
  48. GRB 260330B: SVOM/VT optical candidate
  49. EP260403a: Einstein Probe detection of an X-ray transient
  50. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  51. GRB 260403A: AstroSat CZTI detection
  52. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  53. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  54. GRB 260402C: AstroSat CZTI detection of a long burst
  55. EP260324A / AT 2026hir: COLIBRÍ optical observations
  56. GRB 260402A: WINTER J-band upper limit
  57. GRB260402A: GROWTH-India Telescope optical upper limit
  58. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  59. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  60. GRB 260401A: SVOM/GRM observation
  61. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  62. GRB 260402A: Kilonova-Catcher optical upper limit
  63. GRB 260402A: MASTER optical observations
  64. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  65. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  66. GRB 260402A: SVOM detection of a burst
  67. EP260329b: Mondy and Assy-Turgen optical upper limits
  68. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  69. EP260321a :Xinglong optical observations
  70. EP260327a: Xinglong optical upper limit
  71. GRB 260330B: SVOM/VT optical upper limits
  72. GRB 260321A: SVOM/ECLAIRs refined analysis
  73. EP260329b: J-band upper limits with WINTER
  74. EP260329a: J-band upper limit with WINTER
  75. GRB 260310A: VLA Multi-frequency Radio Observations
  76. GRB 260330B: LCO optical upper limits
  77. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  78. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  79. EP260329a: COLIBRÍ optical upper limit
  80. EP260329a: EP-FXT follow up observation
  81. EP260329a: NOT optical counterpart candidate
  82. EP260329b: Optical follow-up with Kinder observations
  83. EP 260329b: COLIBRÍ optical observations
  84. EP260329a: Optical upper limit with Kinder observations
  85. EP260329b: LCO optical observations of the counterpart
  86. EP260329b: Einstein Probe detection of an X-ray transient
  87. EP260329a: Einstein Probe detection of an X-ray transient
  88. EP-WXT trigger 01709259209: TRT optical counterpart detection
  89. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  90. GRID detection of GRB 260326A
  91. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  92. EP260327a: SVOM/VT optical upper limits
  93. EP260327a: WINTER J-band upper limit
  94. EP260327a: COLIBRÍ optical upper limits
  95. GRB 260327A: AstroSat CZTI detection of a long burst
  96. EP260327a: Gemini-North optical upper limits
  97. EP260324a: GROWTH-India Telescope optical observation
  98. EP260327a: Einstein Probe detection of an X-ray transient
  99. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  100. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope

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