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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"

21264 results found.

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

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