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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"

16109 results found.

  1. EP260610b: SVOM/VT optical confirmation with blue color
  2. GRB 260515A: SOAR optical observations
  3. EP260610b: Gemini North optical counterpart candidate
  4. EP260610a: SVOM/VT optical upper limits
  5. EP260610a: COLIBRÍ optical upper limits
  6. GRB 260604C: further SAO RAS optical observations
  7. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  8. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  9. GRB 260604C: SVOM/C-GFT upper limit
  10. GRB 260608A: SVOM detection of a burst
  11. GRB 260607A: TRT optical observations
  12. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  13. GRB 260604A: SVOM/GRM detection
  14. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  15. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  16. GRB 260604C: 6 GHz VLA observations
  17. GRB 260604C: SAO RAS optical observations
  18. GRB 260604C: GRANDMA observations
  19. GRB 260604B: SVOM/GRM detection
  20. EP260603a: COLIBRÍ optical upper limit
  21. GRB 260604C: LCO optical upper limit
  22. GRB 260604C: Liverpool Telescope optical detection
  23. EP260602d: EP-FXT follow-up observation
  24. GRB 260604C: GOTO detections of the optical afterglow
  25. GRB 260604C: Correction to GCN 44828
  26. GRB 260604C: Kilonova-Catcher optical afterglow detection
  27. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  28. GRB 260604C: Jinshan optical observations
  29. EP260602b: J-band upper limit with WINTER
  30. GRB 260604C: LAST detection of optical counterpart candidate
  31. GRB 260604C: MASTER OT J145749.59+284903.0 optical counterpart discovery
  32. GRB 260604C: SVOM detection of a long burst
  33. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  34. GRB 260603A: NOT optical observations
  35. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  36. EP260602a: EP-FXT follow-up observation
  37. EP260602d: Optical Upper limits with kinder observations
  38. EP260602b: Liverpool Telescope observations
  39. EP260602a: Liverpool Telescope optical upper limits
  40. EP260602b: Liverpool Telescope and LCO observations
  41. EP260602a: GTC and Liverpool Telescope optical observations
  42. GRB 260603A: EP-FXT follow-up observation
  43. GRB 260601B / EP260601a: Mondy optical upper limit
  44. EP260602b: EP-FXT follow-up observation
  45. GRB 260603A: Kilonova-Catcher optical upper limit
  46. GRB 260603A: SVOM/VT optical observations
  47. EP260602a: NOT NIR J-band observations
  48. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  49. EP260602a: SVOM/VT optical magnitudes correction
  50. GRB 260601A: SVOM/GRM observation of a short burst
  51. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  52. EP260602a: COLIBRÍ optical observations
  53. GRB260601B/EP260601a: NOT near-infrared observations
  54. EP260602b: Einstein Probe detection of a fast X-ray transient
  55. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  56. EP260602a: SVOM/VT optical candidate
  57. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  58. GRB 260601B/EP260601a: J-band upper limit with WINTER
  59. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  60. EP260530a/AT 2026nwl: KAIT optical observations
  61. EP260602a: Optical upper limits with Kinder observations
  62. GRB 260601B/EP260601a: SVOM/VT optical observations
  63. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  64. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  65. GRB 260516D: VLA radio detection
  66. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  67. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  68. AT2026nik: EP-FXT X-ray counterpart
  69. AT 2026nuz: COLIBRÍ optical observations
  70. EP260527a/GRB 260527A: further FTW optical and NIR observations
  71. GRB 260527A / EP260527a: VLA radio detection
  72. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  73. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  74. GRB 260529A: GOTO tentative optical afterglow candidate
  75. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  76. EP260526a: SVOM/VT optical upper limits
  77. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  78. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  79. EP260527a / GRB 260527A: NOT optical observations
  80. GRB 260527A/EP260527a: FTW optical and NIR observations
  81. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  82. EP260527a/GRB 260527A: EP-FXT follow-up observation
  83. EP260527a: SVOM/VT optical observation
  84. EP260527a: COLIBRÍ optical detection
  85. EP260526a: LCO optical upper limits
  86. EP260526.405: COLIBRÍ optical upper limits
  87. EP-WXT 01709266106: NOT optical upper limits
  88. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  89. GRB 260522A: GOTO optical upper limit
  90. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  91. GRB 260511A: iTelescope T-75 optical detection
  92. GRB 260520B: SVOM/GRM observation
  93. GRB 260421B: radio detection with the VLA
  94. GRB 260509A: CrAO ZTSh optical upper limit (Duplicate Submission)
  95. GRB 260509A: CrAO ZTSh optical upper limit
  96. GRB 260516D: EP-FXT follow-up observation
  97. GRB 260516D: GOTO optical counterpart detection
  98. GRB 260516D: LCO optical observations
  99. GRB 260515A: further Liverpool Telescope observations
  100. GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations

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