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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"

21769 results found.

  1. GRB 260511A: SVOM/VT optical observation with VHF data
  2. GRB 260511A: KAIT optical afterglow observations
  3. GRB 260511A: LCO optical afterglow detection
  4. GRB 260511A: SVOM/COLIBRÍ (FM-GFT) optical counterpart
  5. GRB 260511A: TRT optical counterpart detection
  6. GRB 260511A: SVOM detection of a bright burst
  7. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  8. GRB 260510B: GOTO early upper limit
  9. GRB 260510C: SVOM detection of a burst
  10. GRB 260510A: GECAM-B observation
  11. GRB 260510B: LCO optical upper limits
  12. EP260509a: Einstein Probe detection of an X-ray transient
  13. GRB 260509A: Liverpool Telescope optical observations
  14. GRB 260510B: SVOM detection of a burst
  15. GRB 260509A: LCO optical observations
  16. SVOM GRB 260509A: MASTER-OAFA optical observation
  17. GRB 260509A: KAIT optical observations
  18. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  19. GRB 260509A: SVOM/VT optical candidate with VHF data
  20. GRB 260509A: LCO optical counterpart detection
  21. GRB 260509A: GOTO optical counterpart candidate
  22. GRB 260509A: SVOM detection of a burst
  23. EP260507a: REM optical/NIR observations
  24. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  25. EP260507a: COLIBRÍ optical observations
  26. EP260507a: NOT optical observations
  27. EP260507a: further Liverpool Telescope observations
  28. EP260507a: Liverpool Telescope optical upper limits
  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 260504B: SVOM/ECLAIRs refined analysis
  34. EP260502a is likely a flaring star
  35. GRB 260504B: SVOM/VT optical upper limits
  36. GRB 260421B: radio observation with the VLA
  37. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  38. Konus-Wind detection of GRB 260504B (short/hard)
  39. GRB 260504B: SVOM/MXT refined analysis and potential detection
  40. GRB 260504B: EP-FXT upper limit
  41. GRB 260502A: SVOM/GRM observation of a short GRB
  42. GRB 260503A: SVOM/GRM observation of a GRB
  43. Konus-Wind detection of GRB 260411C
  44. GRB 260504B: REM optical/NIR observations
  45. GRB 260504B: LCO z-band upper limit
  46. SVOM GRB 260504B: MASTER-OAFA optical observations
  47. GRB 260504B: SVOM detection of a short burst
  48. Fermi GRB 260504A: Global MASTER-Net observations report
  49. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  50. EP260502a: Einstein Probe detection of an X-ray transient
  51. GRB 260429A: SVOM/GRM observation of a short burst
  52. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  53. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  54. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  55. EP260429a: LCO optical upper limits
  56. EP260430a: LCO optical upper limits
  57. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  58. EP260430a: Einstein Probe detection of an X-ray transient
  59. EP260429a: EP-WXT detection of a fast X-ray transient
  60. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  61. EP260416a: Mondy and Terskol optical upper limits
  62. GRB 260424B: COLIBRÍ optical upper limit
  63. Konus-Wind detection of GRB 260424B
  64. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  65. GRB 260401A: cubesat Avion detection
  66. EP260321a: Upper limits from ATCA radio observations
  67. GRB 260421B: Kilonova-Catcher optical afterglow detection
  68. EP260416a: Mondy optical observations
  69. GRB 260421B: SVOM/ECLAIRs refined analysis
  70. GRB 260421B: 3.6m DOT optical observation
  71. EP260416a: ZTSh R band observations
  72. GRB 260421B: SVOM/GRM observation
  73. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  74. GOTO26djh/AT2026jpw: ATCA radio detection
  75. GRB 260421B: J-band upper limit with WINTER
  76. GRB 260421B: LCO optical counterpart detection
  77. GOTO26djh/AT2026jpw: radio detection at 15GHz
  78. GRB 260421B: SVOM/VT optical observations
  79. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  80. GRB 260310A: Late-time Chandra X-ray Detection
  81. EP260416a: 1.3m DFOT optical observation
  82. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  83. GRB 260421B: LCO optical afterglow confirmation
  84. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  85. GRB 260421B: TRT optical counterpart detection
  86. GRB 260421B: SVOM detection of a long burst
  87. EP260321a: VLA radio follow-up
  88. GRB 260412A: LCOGT Optical Upper Limits
  89. EP260416a: Optical follow-up observations with Kinder
  90. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  91. GRB 260417A: SVOM/GRM observation
  92. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  93. EP260417a: GROWTH-India Telescope optical upper limit
  94. EP260417b: GROWTH-India Telescope optical upper limit
  95. EP260416a: Ondrejov D50 optical detection
  96. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  97. EP260416a: GMG Optical Observation
  98. Konus-Wind detection of GRB 260411B
  99. EP260416a: LCO observations confirm end of flaring phase
  100. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope

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