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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"

14844 results found.

  1. GRB 260401A: cubesat Avion detection
  2. GRB 260424A: AstroSat CZTI detection of a long burst
  3. GRB 260421B: Kilonova-Catcher optical afterglow detection
  4. GRB 260421B: Insight-HXMT/HE detection
  5. EP260416a: Mondy optical observations
  6. GRB 260421B: 3.6m DOT optical observation
  7. EP260416a: ZTSh R band observations
  8. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  9. GRB 260419A: AstroSat CZTI detection
  10. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  11. GRB 260421B: EP-FXT follow-up observation
  12. GOTO26djh/AT2026jpw: ATCA radio detection
  13. GRB 260421B: J-band upper limit with WINTER
  14. GRB 260421B: LCO optical counterpart detection
  15. GRB 260421A: AstroSat CZTI detection
  16. GOTO26djh/AT2026jpw: radio detection at 15GHz
  17. GRB 260412A: SVOM/ECLAIRs refined analysis
  18. GRB 260421B: SVOM/VT optical observations
  19. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  20. GRB 260310A: Late-time Chandra X-ray Detection
  21. GRB 260418A: Insight-HXMT/HE detection
  22. EP260416a: 1.3m DFOT optical observation
  23. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  24. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  25. GRB 260421C: Fermi GBM Final Real-time Localization
  26. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  27. GRB 260421B: BOOTES-7 early optical afterglow detection
  28. GRB 260421B: LCO optical afterglow confirmation
  29. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  30. GRB 260421B: TRT optical counterpart detection
  31. GRB 260421B: SVOM detection of a long burst
  32. GRB 260421B: Fermi GBM Final Real-time Localization
  33. GRB 260421A: Fermi GBM Final Real-time Localization
  34. EP260416a: Optical follow-up observations with Kinder
  35. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  36. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  37. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  38. GRB 260419B: Fermi GBM Final Real-time Localization
  39. GRB 260419A: Fermi GBM Final Real-time Localization
  40. EP260417a: GROWTH-India Telescope optical upper limit
  41. EP260416a: Ondrejov D50 optical detection
  42. GRB 260418B: Fermi GBM Final Real-time Localization
  43. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  44. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  45. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  46. GRB 260418A: Fermi GBM Final Real-time Localization
  47. Konus-Wind detection of GRB 260411B
  48. GRB 260417B: Fermi GBM Final Real-time Localization
  49. GRB 260417A: AstroSat CZTI detection
  50. IPN triangulation of GRB 260411B
  51. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  52. EP260417a: TRT optical counterpart detection
  53. EP260417a: Einstein Probe detection of an X-ray transient
  54. EP260417b: Einstein Probe detection of a fast X-ray transient
  55. GRB 260414A: Insight-HXMT/HE detection
  56. EP260416a: WFST optical observations and rebrightening
  57. GRB 260417A: Fermi GBM Final Real-time Localization
  58. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  59. GRB 260415B: Glowbug gamma-ray detection
  60. GRB 260411B: Glowbug gamma-ray detection
  61. GRB 260415A: Insight-HXMT/HE detection
  62. EP260416a: COLIBRÍ optical counterpart candidate
  63. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  64. EP260416a: Einstein Probe detection of an X-ray transient
  65. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  66. GRB 260415B: NuSTAR detection of long prompt emission
  67. GRB 260415B: Fermi GBM Final Localization
  68. GRB 260415A: Fermi GBM Final Real-time Localization
  69. GRB 260414A: Glowbug gamma-ray detection
  70. EP260321a: CMO SAI J,K observations
  71. GRB 260412A: Insight-HXMT/HE detection
  72. GRB 260414A: Fermi GBM Final Real-time Localization
  73. GRB 260410A: Glowbug gamma-ray detection of a short burst
  74. GRB 260413A: Fermi GBM Final Real-time Localization
  75. GRB 260410B: Insight-HXMT/HE detection
  76. GRB 260410A: Insight-HXMT/HE detection
  77. Konus-Wind detection of GRB 260410A (short/hard)
  78. EP260321a: SVOM/VT optical observations and color changes around peak
  79. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  80. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  81. GRB 260411B: Fermi-LAT detection
  82. GRB 260412A: SVOM detection of a long burst
  83. GRB 260412A: Fermi GBM Final Real-time Localization
  84. GRB 260411B: COLIBRÍ optical observations
  85. GRB 260411B: Ondrejov D50 optical afterglow detection
  86. GRB260411B: 3.6m DOT optical observation
  87. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  88. GRB 260409A: Insight-HXMT/HE detection
  89. GRB 260411B: Fermi GBM Detection
  90. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  91. GRB 260411B: Fermi GBM Final Real-time Localization
  92. GRB 260411A: Fermi GBM Final Real-time Localization
  93. EP-WXT01709259790: Optical Upper limits with kinder observations
  94. GRB 260410B: SVOM/GRM detection of a short faint burst
  95. GRB 260410B: Fermi GBM Final Real-time Localization
  96. EP-WXT01709259790: Xinglong optical upper limit
  97. GRB 260410A: Fermi-LAT detection
  98. GRB 260410A: Fermi GBM Final Real-time Localization
  99. EP260321a: Chandra X-ray Non-detection
  100. GRB 260409A: Fermi GBM Final Real-time Localization

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