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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"

20901 results found.

  1. GRB 260610b: Liverpool Telescope optical observations
  2. IceCube-260610A: No candidates from the Zwicky Transient Facility
  3. IceCube-260610A: EP-FXT follow-up observation
  4. The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
  5. GRB 260610B / AT2026owq: SVOM/VT optical observations
  6. GRB 260610B / AT2026owq: OASDG optical observations
  7. GRB 260610B: IAC-80 Optical observations
  8. GRB 260610B / AT2026owq: SAO RAS optical observations
  9. EP260610b: GTC likely spectroscopic redshift z = 1.10
  10. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  11. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  12. GRB 260610B / AT2026owq: Early ATLAS observations
  13. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  14. EP260610b: COLIBRÍ optical observations
  15. GRB 260610B: DDOTI optical observations
  16. EP260610b: MAO/AZT-22 optical observations
  17. GRB 260610B: GOTO optical counterpart candidate
  18. EP260610b: SVOM/VT optical confirmation with blue color
  19. GRB 260515A: SOAR optical observations
  20. EP260610b: Gemini North optical counterpart candidate
  21. GRB 260604C: SVOM/ECLAIRs refined analysis
  22. GRB 260608A: SVOM/ECLAIRs refined analysis
  23. GRB 260604C: further SAO RAS optical observations
  24. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  25. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  26. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  27. GRB 260604C: SVOM/C-GFT upper limit
  28. GRB 260607A: TRT optical observations
  29. GRB 260604C: GRANDMA further observations
  30. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  31. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  32. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  33. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  34. GRB 260604C: 6 GHz VLA observations
  35. GRB 260604C: SAO RAS optical observations
  36. GRB 260604C: GRANDMA observations
  37. GRB260603A: SVOM/ECLAIRs refined analysis
  38. GRB 260604C: Liverpool Telescope optical detection
  39. EP260602d: EP-FXT follow-up observation
  40. GRB 260527A/EP260527a: 6 GHz VLA observations
  41. GRB 260604C: GOTO detections of the optical afterglow
  42. GRB 260604C: Kilonova-Catcher optical afterglow detection
  43. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  44. GRB 260604C: Jinshan optical observations
  45. EP260602d: J-band upper limit with WINTER
  46. EP260602b: J-band upper limit with WINTER
  47. GRB 260604C: LAST detection of optical counterpart candidate
  48. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  49. Fermi GRB 260604C: Global MASTER-Net observations report
  50. Fermi GRB 260604C: Global MASTER-Net observations report
  51. SVOM GRB260604.85: Global MASTER-Net observations report
  52. GRB 260604C: SVOM detection of a long burst
  53. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  54. GRB 260603A: NOT optical observations
  55. EP260603a: Global MASTER-Net observations report
  56. EP260603a: Einstein Probe detection of a fast X-ray transient
  57. EP260602d: Optical Upper limits with kinder observations
  58. EP260602b: Liverpool Telescope observations
  59. EP260602a: Liverpool Telescope optical upper limits
  60. EP260602b: Liverpool Telescope and LCO observations
  61. EP260602a: GTC and Liverpool Telescope optical observations
  62. GRB 260603A: Kilonova-Catcher optical upper limit
  63. GRB 260603A: SVOM/VT optical observations
  64. EP260602a: NOT NIR J-band observations
  65. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  66. Fermi trigger No 802141998: Global MASTER-Net observations report
  67. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  68. EP260602a: COLIBRÍ optical observations
  69. GRB260601B/EP260601a: NOT near-infrared observations
  70. SVOM GRB260603.23: Global MASTER-Net observations report
  71. Fermi GRB 260602B: Global MASTER-Net observations report
  72. Fermi GRB 260602B: Global MASTER-Net observations report
  73. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  74. EP260602a: SVOM/VT optical candidate
  75. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  76. GRB 260601B/EP260601a: J-band upper limit with WINTER
  77. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  78. EP260530a/AT 2026nwl: KAIT optical observations
  79. EP260602a: Optical upper limits with Kinder observations
  80. GRB 260601B/EP260601a: SVOM/VT optical observations
  81. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  82. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  83. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  84. GRB 260516D: VLA radio detection
  85. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  86. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  87. Fermi GRB 260601A: Global MASTER-Net observations report
  88. AT2026nik: EP-FXT X-ray counterpart
  89. Fermi trigger No 801900520: Global MASTER-Net observations report
  90. AT 2026nuz: COLIBRÍ optical observations
  91. EP260527a/GRB 260527A: further FTW optical and NIR observations
  92. GRB 260527A / EP260527a: VLA radio detection
  93. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  94. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  95. GRB 260529A: GOTO tentative optical afterglow candidate
  96. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  97. Fermi GRB 260529A: Global MASTER-Net observations report
  98. EP260526a: SVOM/VT optical upper limits
  99. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  100. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart

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