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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"

22060 results found.

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

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