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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"

23601 results found.

  1. GRB 260421A: AstroSat CZTI detection
  2. GRB 260412A: SVOM/ECLAIRs refined analysis
  3. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  4. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  5. GRB 260421B: BOOTES-7 early optical afterglow detection
  6. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  7. GRB 260421B: TRT optical counterpart detection
  8. EP260321a: VLA radio follow-up
  9. EP260416a: Optical follow-up observations with Kinder
  10. EP-WXT trigger 01709260303: KAIT optical observations
  11. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  12. EP260416a: Ondrejov D50 optical detection
  13. Konus-Wind detection of GRB 260411B
  14. GRB 260417A: AstroSat CZTI detection
  15. IPN triangulation of GRB 260411B
  16. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  17. EP260417a: TRT optical counterpart detection
  18. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  19. EP-WXT trigger 01709259586: KAIT optical observations
  20. EP260416a: KAIT optical upper limit
  21. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  22. GRB 260415B: Glowbug gamma-ray detection
  23. GRB 260411B: Glowbug gamma-ray detection
  24. EP260416a: COLIBRÍ optical counterpart candidate
  25. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  26. EP260416a: Einstein Probe detection of an X-ray transient
  27. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  28. GRB 260414A: Glowbug gamma-ray detection
  29. EP260321a: CMO SAI J,K observations
  30. GRB 260412A: Insight-HXMT/HE detection
  31. GRB 260410A: Glowbug gamma-ray detection of a short burst
  32. Konus-Wind detection of GRB 260410A (short/hard)
  33. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  34. GRB 260412A: GECAM-B observation of a long burst
  35. GRB 260411B: COLIBRÍ optical observations
  36. GRB 260411B: Ondrejov D50 optical afterglow detection
  37. GRB 260409A: Insight-HXMT/HE detection
  38. GRB 260411B: GOTO optical counterpart candidate
  39. GRB 260410A: COLIBRÍ optical upper limit
  40. EP-WXT01709259790: Optical Upper limits with kinder observations
  41. The EP-WXT trigger 01709259790 is likely a flaring star
  42. EP-WXT01709259790: Xinglong optical upper limit
  43. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  44. GRB 260407A: GECAM-A detection
  45. GRB 260407A: Insight-HXMT/HE detection
  46. EP260409a: COLIBRÍ optical upper limits
  47. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  48. EP260321a: VLA radio detection
  49. GRB 260407A: Glowbug gamma-ray detection
  50. GRB 260402A: SVOM/ECLAIRs refined analysis
  51. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  52. GRB 260310A / AT2026fgk: X-ray rebrightening
  53. EP260402a / GRB 260402A: Mephisto optical upper limits
  54. EP-WXT01709259586: Xinglong optical upper limit
  55. EP260403a: Mephisto optical upper limits
  56. EP260402a/GRB 260402A: Xinglong optical upper limit
  57. EP260321a: Upper limits from VLA radio observations
  58. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  59. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  60. GRB 260330B: SVOM/ECLAIRs refined analysis
  61. EP260403a: LCO optical observations of the counterpart
  62. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  63. EP260403a: LCO optical counterpart detection
  64. EP260403a: COLIBRÍ optical counterpart candidate
  65. GRB 260403A: AstroSat CZTI detection
  66. GRB 260402C: AstroSat CZTI detection of a long burst
  67. EP260324A / AT 2026hir: COLIBRÍ optical observations
  68. GRB 260402A: WINTER J-band upper limit
  69. GRB 260402A: Kilonova-Catcher optical upper limit
  70. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  71. GRB 260402A: SVOM detection of a burst
  72. GRB 260401A: Fermi GBM Observation
  73. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  74. GRB 260401A: MAXI/GSC detection
  75. EP260329b: Mondy and Assy-Turgen optical upper limits
  76. EP260321a :Xinglong optical observations
  77. EP260327a: Xinglong optical upper limit
  78. EP260329b: GOTO detection of optical counterpart
  79. Konus-Wind detection of GRB 260320A
  80. Konus-Wind detection of GRB 260316B
  81. GRB 260321A: SVOM/ECLAIRs refined analysis
  82. EP260329b: J-band upper limits with WINTER
  83. EP260329a: J-band upper limit with WINTER
  84. GRB 260330A: Glowbug gamma-ray detection
  85. GRB 260310A: VLA Multi-frequency Radio Observations
  86. EP260329a: COLIBRÍ optical upper limit
  87. EP260329a: NOT optical counterpart candidate
  88. GRB 260327A: Insight-HXMT/HE detection
  89. EP260329b: Optical follow-up with Kinder observations
  90. EP 260329b: COLIBRÍ optical observations
  91. EP260329a: Optical upper limit with Kinder observations
  92. EP260329b: LCO optical observations of the counterpart
  93. EP-WXT trigger 01709259209: TRT optical counterpart detection
  94. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  95. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  96. EP260327a: WINTER J-band upper limit
  97. EP260327a: COLIBRÍ optical upper limits
  98. GRB 260327A: AstroSat CZTI detection of a long burst
  99. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  100. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk

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