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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"

21767 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: GOTO early upper limit
  7. GRB 260510C: SVOM detection of a burst
  8. GRB 260510A: GECAM-B observation
  9. GRB 260510B: LCO optical upper limits
  10. EP260509a: Einstein Probe detection of an X-ray transient
  11. GRB 260509A: Liverpool Telescope optical observations
  12. GRB 260510B: SVOM detection of a burst
  13. GRB 260509A: LCO optical observations
  14. SVOM GRB 260509A: MASTER-OAFA optical observation
  15. GRB 260509A: KAIT optical observations
  16. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  17. GRB 260509A: SVOM/VT optical candidate with VHF data
  18. GRB 260509A: LCO optical counterpart detection
  19. GRB 260509A: GOTO optical counterpart candidate
  20. GRB 260509A: SVOM detection of a burst
  21. EP260507a: REM optical/NIR observations
  22. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  23. EP260507a: COLIBRÍ optical observations
  24. EP260507a: NOT optical observations
  25. EP260507a: further Liverpool Telescope observations
  26. EP260507a: Liverpool Telescope optical upper limits
  27. EP260507a: TRT optical counterpart detection
  28. EP260507a: Kinder optical counterpart candidate
  29. EP260507a: LCO optical counterpart
  30. EP260507a: Einstein Probe detection of an X-ray transient
  31. GRB 260504B: SVOM/ECLAIRs refined analysis
  32. EP260502a is likely a flaring star
  33. GRB 260504B: SVOM/VT optical upper limits
  34. GRB 260421B: radio observation with the VLA
  35. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  36. Konus-Wind detection of GRB 260504B (short/hard)
  37. GRB 260504B: SVOM/MXT refined analysis and potential detection
  38. GRB 260504B: EP-FXT upper limit
  39. GRB 260502A: SVOM/GRM observation of a short GRB
  40. GRB 260503A: SVOM/GRM observation of a GRB
  41. Konus-Wind detection of GRB 260411C
  42. GRB 260504B: REM optical/NIR observations
  43. GRB 260504B: LCO z-band upper limit
  44. SVOM GRB 260504B: MASTER-OAFA optical observations
  45. GRB 260504B: SVOM detection of a short burst
  46. Fermi GRB 260504A: Global MASTER-Net observations report
  47. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  48. EP260502a: Einstein Probe detection of an X-ray transient
  49. GRB 260429A: SVOM/GRM observation of a short burst
  50. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  51. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  52. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  53. EP260429a: LCO optical upper limits
  54. EP260430a: LCO optical upper limits
  55. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  56. EP260430a: Einstein Probe detection of an X-ray transient
  57. EP260429a: EP-WXT detection of a fast X-ray transient
  58. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  59. EP260416a: Mondy and Terskol optical upper limits
  60. GRB 260424B: COLIBRÍ optical upper limit
  61. Konus-Wind detection of GRB 260424B
  62. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  63. GRB 260401A: cubesat Avion detection
  64. EP260321a: Upper limits from ATCA radio observations
  65. GRB 260421B: Kilonova-Catcher optical afterglow detection
  66. EP260416a: Mondy optical observations
  67. GRB 260421B: SVOM/ECLAIRs refined analysis
  68. GRB 260421B: 3.6m DOT optical observation
  69. EP260416a: ZTSh R band observations
  70. GRB 260421B: SVOM/GRM observation
  71. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  72. GOTO26djh/AT2026jpw: ATCA radio detection
  73. GRB 260421B: J-band upper limit with WINTER
  74. GRB 260421B: LCO optical counterpart detection
  75. GOTO26djh/AT2026jpw: radio detection at 15GHz
  76. GRB 260421B: SVOM/VT optical observations
  77. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  78. GRB 260310A: Late-time Chandra X-ray Detection
  79. EP260416a: 1.3m DFOT optical observation
  80. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  81. GRB 260421B: LCO optical afterglow confirmation
  82. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  83. GRB 260421B: TRT optical counterpart detection
  84. GRB 260421B: SVOM detection of a long burst
  85. EP260321a: VLA radio follow-up
  86. GRB 260412A: LCOGT Optical Upper Limits
  87. EP260416a: Optical follow-up observations with Kinder
  88. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  89. GRB 260417A: SVOM/GRM observation
  90. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  91. EP260417a: GROWTH-India Telescope optical upper limit
  92. EP260417b: GROWTH-India Telescope optical upper limit
  93. EP260416a: Ondrejov D50 optical detection
  94. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  95. EP260416a: GMG Optical Observation
  96. Konus-Wind detection of GRB 260411B
  97. EP260416a: LCO observations confirm end of flaring phase
  98. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  99. EP260417a: TRT optical counterpart detection
  100. EP260417a: Einstein Probe detection of an X-ray transient

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