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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"

22912 results found.

  1. GRB 260511A: LCO optical afterglow detection
  2. GRB 260511A: SVOM/COLIBRÍ (FM-GFT) optical counterpart
  3. GRB 260511A: TRT optical counterpart detection
  4. GRB 260511A: SVOM detection of a bright burst
  5. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  6. GRB 260510B: SVOM/VT optical upper limits
  7. GRB 260510C: SVOM/VT optical upper limits
  8. Fermi GBM Sub-Threshold Detection of GRB 260510B
  9. GRB 260510C: SVOM detection of a burst
  10. GRB 260510B: LCO optical upper limits
  11. EP260509a: Einstein Probe detection of an X-ray transient
  12. GRB 260509A: Liverpool Telescope optical observations
  13. GRB 260510B: SVOM detection of a burst
  14. GRB 260509A: LCO optical observations
  15. SVOM GRB 260509A: MASTER-OAFA optical observation
  16. GRB 260509A: KAIT optical observations
  17. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  18. GRB 260509A: SVOM/VT optical candidate with VHF data
  19. GRB 260509A: LCO optical counterpart detection
  20. GRB 260509A: SVOM detection of a burst
  21. GRB 260506B: AstroSat CZTI detection
  22. EP260507a: REM optical/NIR observations
  23. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  24. EP260507a: COLIBRÍ optical observations
  25. EP260507a: NOT optical observations
  26. EP260507a: further Liverpool Telescope observations
  27. EP260507a: Liverpool Telescope optical upper limits
  28. EP260507a: GOTO optical counterpart detection
  29. EP260507a: TRT optical counterpart detection
  30. EP260507a: Kinder optical counterpart candidate
  31. EP260507a: LCO optical counterpart
  32. EP260507a: Einstein Probe detection of an X-ray transient
  33. GRB 260503A: GECAM-B observation of a burst
  34. GRB 260430B: Glowbug gamma-ray detection
  35. GRB 260421B: radio observation with the VLA
  36. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  37. GRB 260502A: SVOM/GRM observation of a short GRB
  38. GRB 260503A: SVOM/GRM observation of a GRB
  39. GRB 260504B: REM optical/NIR observations
  40. IPN triangulation of GRB 260429A
  41. IPN triangulation of GRB 260428A
  42. GRB 260504B: LCO z-band upper limit
  43. SVOM GRB 260504B: MASTER-OAFA optical observations
  44. GRB 260504B: SVOM detection of a short burst
  45. GRB 260503A: Fermi GBM Final Real-time Localization
  46. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  47. IPN triangulation of a bright burst from SGR 1E1841-045
  48. GRB 260429B / EP260429a: AstroSat CZTI detection
  49. EP260502a: BOOTES-7: early optical upper limit
  50. EP260502a: Las Cumbres upper limit
  51. EP260502a: Einstein Probe detection of an X-ray transient
  52. GRB 260429A: SVOM/GRM observation of a short burst
  53. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  54. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  55. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  56. EP260429a: LCO optical upper limits
  57. EP260430a: LCO optical upper limits
  58. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  59. EP260430a: Einstein Probe detection of an X-ray transient
  60. EP260429a: EP-WXT detection of a fast X-ray transient
  61. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  62. GRB 260428A: AstroSat CZTI detection
  63. EP260416a: Mondy and Terskol optical upper limits
  64. GRB 260424B: Glowbug gamma-ray detection of a short burst
  65. GRB 260424B: COLIBRÍ optical upper limit
  66. Konus-Wind detection of GRB 260424B
  67. IPN triangulation of GRB 260424B (short)
  68. GRB 260401A: cubesat Avion detection
  69. GRB 260424A: AstroSat CZTI detection of a long burst
  70. EP260321a: Upper limits from ATCA radio observations
  71. GRB 260421B: Kilonova-Catcher optical afterglow detection
  72. EP260416a: Mondy optical observations
  73. GRB 260421B: 3.6m DOT optical observation
  74. EP260416a: ZTSh R band observations
  75. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  76. GRB 260421B: SVOM/GRM observation
  77. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  78. GOTO26djh/AT2026jpw: ATCA radio detection
  79. GRB 260421B: J-band upper limit with WINTER
  80. GRB 260421B: LCO optical counterpart detection
  81. GOTO26djh/AT2026jpw: radio detection at 15GHz
  82. GRB 260421B: SVOM/VT optical observations
  83. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  84. GRB 260310A: Late-time Chandra X-ray Detection
  85. EP260416a: 1.3m DFOT optical observation
  86. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  87. GRB 260421B: LCO optical afterglow confirmation
  88. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  89. GRB 260421B: TRT optical counterpart detection
  90. GRB 260421B: SVOM detection of a long burst
  91. EP260321a: VLA radio follow-up
  92. GRB 260412A: LCOGT Optical Upper Limits
  93. EP260416a: Optical follow-up observations with Kinder
  94. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  95. GRB 260417A: SVOM/GRM observation
  96. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  97. EP260417a: GROWTH-India Telescope optical upper limit
  98. EP260417b: GROWTH-India Telescope optical upper limit
  99. EP260416a: Ondrejov D50 optical detection
  100. EP260416a: VLT/FORS2 spectroscopic redshift confirmation

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