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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"

14830 results found.

  1. GRB 260421A: AstroSat CZTI detection
  2. GOTO26djh/AT2026jpw: radio detection at 15GHz
  3. GRB 260412A: SVOM/ECLAIRs refined analysis
  4. GRB 260421B: SVOM/VT optical observations
  5. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  6. GRB 260310A: Late-time Chandra X-ray Detection
  7. GRB 260418A: Insight-HXMT/HE detection
  8. EP260416a: 1.3m DFOT optical observation
  9. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  10. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  11. GRB 260421C: Fermi GBM Final Real-time Localization
  12. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  13. GRB 260421B: BOOTES-7 early optical afterglow detection
  14. GRB 260421B: LCO optical afterglow confirmation
  15. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  16. GRB 260421B: TRT optical counterpart detection
  17. GRB 260421B: SVOM detection of a long burst
  18. GRB 260421B: Fermi GBM Final Real-time Localization
  19. GRB 260421A: Fermi GBM Final Real-time Localization
  20. EP260416a: Optical follow-up observations with Kinder
  21. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  22. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  23. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  24. GRB 260419B: Fermi GBM Final Real-time Localization
  25. GRB 260419A: Fermi GBM Final Real-time Localization
  26. EP260417a: GROWTH-India Telescope optical upper limit
  27. EP260416a: Ondrejov D50 optical detection
  28. GRB 260418B: Fermi GBM Final Real-time Localization
  29. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  30. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  31. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  32. GRB 260418A: Fermi GBM Final Real-time Localization
  33. Konus-Wind detection of GRB 260411B
  34. GRB 260417B: Fermi GBM Final Real-time Localization
  35. GRB 260417A: AstroSat CZTI detection
  36. IPN triangulation of GRB 260411B
  37. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  38. EP260417a: TRT optical counterpart detection
  39. EP260417a: Einstein Probe detection of an X-ray transient
  40. EP260417b: Einstein Probe detection of a fast X-ray transient
  41. GRB 260414A: Insight-HXMT/HE detection
  42. EP260416a: WFST optical observations and rebrightening
  43. GRB 260417A: Fermi GBM Final Real-time Localization
  44. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  45. GRB 260415B: Glowbug gamma-ray detection
  46. GRB 260411B: Glowbug gamma-ray detection
  47. GRB 260415A: Insight-HXMT/HE detection
  48. EP260416a: COLIBRÍ optical counterpart candidate
  49. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  50. EP260416a: Einstein Probe detection of an X-ray transient
  51. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  52. GRB 260415B: NuSTAR detection of long prompt emission
  53. GRB 260415B: Fermi GBM Final Localization
  54. GRB 260415A: Fermi GBM Final Real-time Localization
  55. GRB 260414A: Glowbug gamma-ray detection
  56. EP260321a: CMO SAI J,K observations
  57. GRB 260412A: Insight-HXMT/HE detection
  58. GRB 260414A: Fermi GBM Final Real-time Localization
  59. GRB 260410A: Glowbug gamma-ray detection of a short burst
  60. GRB 260413A: Fermi GBM Final Real-time Localization
  61. GRB 260410B: Insight-HXMT/HE detection
  62. GRB 260410A: Insight-HXMT/HE detection
  63. Konus-Wind detection of GRB 260410A (short/hard)
  64. EP260321a: SVOM/VT optical observations and color changes around peak
  65. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  66. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  67. GRB 260411B: Fermi-LAT detection
  68. GRB 260412A: SVOM detection of a long burst
  69. GRB 260412A: Fermi GBM Final Real-time Localization
  70. GRB 260411B: COLIBRÍ optical observations
  71. GRB 260411B: Ondrejov D50 optical afterglow detection
  72. GRB260411B: 3.6m DOT optical observation
  73. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  74. GRB 260409A: Insight-HXMT/HE detection
  75. GRB 260411B: Fermi GBM Detection
  76. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  77. GRB 260411B: Fermi GBM Final Real-time Localization
  78. GRB 260411A: Fermi GBM Final Real-time Localization
  79. EP-WXT01709259790: Optical Upper limits with kinder observations
  80. GRB 260410B: SVOM/GRM detection of a short faint burst
  81. GRB 260410B: Fermi GBM Final Real-time Localization
  82. EP-WXT01709259790: Xinglong optical upper limit
  83. GRB 260410A: Fermi-LAT detection
  84. GRB 260410A: Fermi GBM Final Real-time Localization
  85. EP260321a: Chandra X-ray Non-detection
  86. GRB 260409A: Fermi GBM Final Real-time Localization
  87. GRB 260407A: GECAM-A detection
  88. GRB 260407A: Insight-HXMT/HE detection
  89. EP260409a: SVOM/VT optical upper limits
  90. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  91. EP260409a: Einstein Probe detection of an X-ray transient
  92. EP260321a: VLA radio detection
  93. GRB 260404A: Fermi GBM Final Localization
  94. GRB 260407A: Glowbug gamma-ray detection
  95. GRB 260310A / AT2026fgk: X-ray rebrightening
  96. EP260402a / GRB 260402A: Mephisto optical upper limits
  97. EP-WXT01709259586: Xinglong optical upper limit
  98. EP260403a: Mephisto optical upper limits
  99. EP260402a/GRB 260402A: Xinglong optical upper limit
  100. EP260321a: Upper limits from VLA radio observations

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