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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"

21264 results found.

  1. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  2. EP260416a: WFST optical observations and rebrightening
  3. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  4. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  5. EP260416a: COLIBRÍ optical counterpart candidate
  6. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  7. EP260416a: Einstein Probe detection of an X-ray transient
  8. GOTO26djh/AT2026jpw : MASTER OT observation
  9. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  10. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  11. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  12. EP260321a: CMO SAI J,K observations
  13. Konus-Wind detection of GRB 260410A (short/hard)
  14. GRB 260411B: Fermi-LAT detection
  15. GRB 260412A: SVOM detection of a long burst
  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: GOTO optical counterpart candidate
  21. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  22. GRB 260410A: COLIBRÍ optical upper limit
  23. EP-WXT01709259790: Optical Upper limits with kinder observations
  24. EP-WXT01709259790: Xinglong optical upper limit
  25. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  26. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  27. EP260409a: COLIBRÍ optical upper limits
  28. EP260409a: Einstein Probe detection of an X-ray transient
  29. EP260321a: VLA radio detection
  30. GRB 260402A: SVOM/ECLAIRs refined analysis
  31. EP260402a / GRB 260402A: Mephisto optical upper limits
  32. EP-WXT01709259586: Xinglong optical upper limit
  33. EP260403a: Mephisto optical upper limits
  34. EP260402a/GRB 260402A: Xinglong optical upper limit
  35. EP260321a: uGMRT observations
  36. EP260405a: GMOS-N optical upper limits
  37. EP260405a: Einstein Probe detection of a fast X-ray transient
  38. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  39. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  40. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  41. GRB 260330B: SVOM/VT further optical observation
  42. EP260403a: LCO optical observations of the counterpart
  43. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  44. EP260403a: LCO optical counterpart detection
  45. EP260403a: COLIBRÍ optical counterpart candidate
  46. GRB 260330B: SVOM/VT optical candidate
  47. EP260403a: Einstein Probe detection of an X-ray transient
  48. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  49. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  50. EP260324A / AT 2026hir: COLIBRÍ optical observations
  51. GRB 260402A: WINTER J-band upper limit
  52. GRB260402A: GROWTH-India Telescope optical upper limit
  53. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  54. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  55. GRB 260401A: SVOM/GRM observation
  56. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  57. GRB 260402A: Kilonova-Catcher optical upper limit
  58. GRB 260402A: MASTER optical observations
  59. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  60. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  61. GRB 260402A: SVOM detection of a burst
  62. EP260329b: Mondy and Assy-Turgen optical upper limits
  63. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  64. EP260321a :Xinglong optical observations
  65. EP260327a: Xinglong optical upper limit
  66. GRB 260330B: SVOM/VT optical upper limits
  67. Konus-Wind detection of GRB 260320A
  68. Konus-Wind detection of GRB 260316B
  69. GRB 260321A: SVOM/ECLAIRs refined analysis
  70. EP260329b: J-band upper limits with WINTER
  71. EP260329a: J-band upper limit with WINTER
  72. GRB 260330B: LCO optical upper limits
  73. GRB 260330B: SVOM detection of a burst
  74. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  75. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  76. EP260329a: COLIBRÍ optical upper limit
  77. EP260329a: EP-FXT follow up observation
  78. EP260329a: NOT optical counterpart candidate
  79. EP260329b: Optical follow-up with Kinder observations
  80. EP 260329b: COLIBRÍ optical observations
  81. EP260329a: Optical upper limit with Kinder observations
  82. EP260329b: LCO optical observations of the counterpart
  83. EP260329b: Einstein Probe detection of an X-ray transient
  84. EP260329a: Einstein Probe detection of an X-ray transient
  85. EP-WXT trigger 01709259209: TRT optical counterpart detection
  86. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  87. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  88. EP260327a: SVOM/VT optical upper limits
  89. EP260327a: WINTER J-band upper limit
  90. EP260327a: COLIBRÍ optical upper limits
  91. GRB 260327A: AstroSat CZTI detection of a long burst
  92. EP260327a: Gemini-North optical upper limits
  93. EP260324a: GROWTH-India Telescope optical observation
  94. EP260327a: Einstein Probe detection of an X-ray transient
  95. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  96. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  97. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  98. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  99. EP260321a: JinShan near-infrared observations
  100. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time

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