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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"

19548 results found.

  1. GRB 260607A: TRT optical observations
  2. GRB 260604A: SVOM/GRM detection
  3. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  4. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  5. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  6. GRB 260604C: 6 GHz VLA observations
  7. GRB 260604C: SAO RAS optical observations
  8. GRB 260604B: SVOM/GRM detection
  9. EP260605a: Einstein Probe detection of a fast X-ray transient
  10. EP260603a: COLIBRÍ optical upper limit
  11. GRB 260604C: LCO optical upper limit
  12. EP260602d: EP-FXT follow-up observation
  13. EP260602c: EP-FXT follow-up observation
  14. GRB 260601B / EP260601a: AstroSat CZTI detection
  15. GRB 260527A/EP260527a: 6 GHz VLA observations
  16. GRB 260604C: Kilonova-Catcher optical afterglow detection
  17. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  18. GRB 260604C: Jinshan optical observations
  19. EP260602d: J-band upper limit with WINTER
  20. EP260602b: J-band upper limit with WINTER
  21. GRB 260604C: LAST detection of optical counterpart candidate
  22. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  23. EP260602a: EP-FXT follow-up observation
  24. EP260603a: Einstein Probe detection of a fast X-ray transient
  25. EP260602d: Optical Upper limits with kinder observations
  26. EP260602b: Liverpool Telescope observations
  27. EP260602a: Liverpool Telescope optical upper limits
  28. EP260602b: Liverpool Telescope and LCO observations
  29. EP260602a: GTC and Liverpool Telescope optical observations
  30. Konus-Wind detection of GRB 260601B/EP260601a
  31. GRB 260601B / EP260601a: Mondy optical upper limit
  32. EP260602b: EP-FXT follow-up observation
  33. GRB 260603A: Kilonova-Catcher optical upper limit
  34. GRB 260603A: SVOM/VT optical observations
  35. EP260602a: NOT NIR J-band observations
  36. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  37. EP260602d: Einstein Probe detection of a fast X-ray transient
  38. GRB 260601A: SVOM/GRM observation of a short burst
  39. EP260602c: Einstein Probe detection of a fast X-ray transient
  40. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  41. EP260602a: COLIBRÍ optical observations
  42. GRB260601B/EP260601a: NOT near-infrared observations
  43. EP260602b: Einstein Probe detection of a fast X-ray transient
  44. EP260602a: SVOM/VT optical candidate
  45. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  46. GRB 260601B/EP260601a: J-band upper limit with WINTER
  47. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  48. EP260530a/AT 2026nwl: KAIT optical observations
  49. EP260602a: Optical upper limits with Kinder observations
  50. EP260602a: Einstein Probe detection of a fast X-ray transient
  51. GRB 260601B/EP260601a: SVOM/VT optical observations
  52. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  53. EP260601a: Einstein Probe detection of an X-ray transient
  54. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  55. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  56. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  57. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  58. AT2026nik: EP-FXT X-ray counterpart
  59. AT 2026nuz: COLIBRÍ optical observations
  60. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  61. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  62. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  63. EP260526a: SVOM/VT optical upper limits
  64. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  65. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  66. EP260527a/GRB 260527A: EP-FXT follow-up observation
  67. EP260527a: SVOM/VT optical observation
  68. EP260527a: COLIBRÍ optical detection
  69. EP260527a: Einstein Probe detection of a fast X-ray transient
  70. EP260526a: LCO optical upper limits
  71. EP260526a: Einstein Probe detection of a fast X-ray transient
  72. GRB 260525A: AstroSat CZTI detection
  73. EP260526.405: COLIBRÍ optical upper limits
  74. The EP-WXT trigger 01709266106 is not a real source
  75. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  76. EP-WXT 01709266106: NOT optical upper limits
  77. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  78. GRB 260511A: iTelescope T-75 optical detection
  79. GRB 260520B: SVOM/GRM observation
  80. Konus-Wind detection of GRB 260519C
  81. GRB 260509A: SVOM/ECLAIRs refined analysis
  82. GRB 260421B: radio detection with the VLA
  83. GRB 260509A: CrAO ZTSh optical upper limit
  84. GRB 260516D: GOTO optical counterpart detection
  85. GRB 260516D: LCO optical observations
  86. GRB 260515A: further Liverpool Telescope observations
  87. GRB 260516D: SVOM/COLIBRÍ (FM-GFT) optical observations
  88. GRB 260516D: GROWTH-India Telescope optical detection
  89. GRB 260516D: SVOM/VT optical bright candidate
  90. GRB 260515A: CrAO ZTSh BVRI optical observations
  91. Konus-Wind detection of GRB 260515A
  92. GRB 260515A: LCO optical counterpart detection
  93. GRB 260515A: SVOM/COLIBRÍ (FM-GFT) optical observations
  94. EP260514a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  95. EP260514a: NOT optical counterpart confirmation
  96. EP260514a: TRT optical counterpart candidate
  97. EP260514a: SVOM/VT optical candidate
  98. GRB 260515A: OHP/T193 optical observations
  99. EP260514a: COLIBRÍ optical upper limits
  100. GRB 260515A: LCO optical observations

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