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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"

18327 results found.

  1. EP260610b: COLIBRÍ optical observations
  2. GRB 260610B: DDOTI optical observations
  3. EP260610b: MAO/AZT-22 optical observations
  4. EP260610b: NOT optical observation
  5. EP260610b: SVOM/VT optical confirmation with blue color
  6. GRB 260515A: SOAR optical observations
  7. EP260610a: SVOM/VT optical upper limits
  8. EP260610b: Einstein Probe detection of an X-ray transient
  9. EP260610a: COLIBRÍ optical upper limits
  10. EP260610a: Einstein Probe detection of a fast X-ray transient
  11. GRB 260604C: further SAO RAS optical observations
  12. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  13. GRB 260608B: Fermi GBM Final Localization
  14. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  15. GRB 260604C: SVOM/C-GFT upper limit
  16. EP260605a: EP-FXT follow-up observation
  17. GRB 260607A: TRT optical observations
  18. GRB 260604A: SVOM/GRM detection
  19. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  20. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  21. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  22. GRB 260604C: 6 GHz VLA observations
  23. GRB 260604C: SAO RAS optical observations
  24. GRB 260604B: SVOM/GRM detection
  25. EP260605a: Einstein Probe detection of a fast X-ray transient
  26. EP260603a: COLIBRÍ optical upper limit
  27. GRB 260604C: LCO optical upper limit
  28. The EP-WXT trigger 01709267001 is likely a flaring star
  29. EP260602d: EP-FXT follow-up observation
  30. EP260602c: EP-FXT follow-up observation
  31. GRB 260527A/EP260527a: 6 GHz VLA observations
  32. GRB 260604C: Kilonova-Catcher optical afterglow detection
  33. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  34. The EP-WXT trigger 01709266798 is likely a flaring star
  35. GRB 260604C: Jinshan optical observations
  36. EP260602d: J-band upper limit with WINTER
  37. EP260602b: J-band upper limit with WINTER
  38. GRB 260604C: LAST detection of optical counterpart candidate
  39. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  40. EP260602a: EP-FXT follow-up observation
  41. EP260603a: Einstein Probe detection of a fast X-ray transient
  42. EP260602d: Optical Upper limits with kinder observations
  43. EP260602b: Liverpool Telescope observations
  44. EP260602a: Liverpool Telescope optical upper limits
  45. EP260602b: Liverpool Telescope and LCO observations
  46. EP260602a: GTC and Liverpool Telescope optical observations
  47. GRB 260603A: EP-FXT follow-up observation
  48. EP260601a/GRB 260601B: EP-FXT follow-up observation
  49. GRB 260601B / EP260601a: Mondy optical upper limit
  50. EP260602b: EP-FXT follow-up observation
  51. GRB 260603A: Kilonova-Catcher optical upper limit
  52. GRB 260603A: SVOM/VT optical observations
  53. EP260602a: NOT NIR J-band observations
  54. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  55. EP260602d: Einstein Probe detection of a fast X-ray transient
  56. GRB 260601A: SVOM/GRM observation of a short burst
  57. EP260602c: Einstein Probe detection of a fast X-ray transient
  58. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  59. EP260602a: COLIBRÍ optical observations
  60. GRB260601B/EP260601a: NOT near-infrared observations
  61. SVOM GRB260603.23: Global MASTER-Net observations report
  62. EP260602b: Einstein Probe detection of a fast X-ray transient
  63. EP260602a: SVOM/VT optical candidate
  64. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  65. GRB 260601B/EP260601a: J-band upper limit with WINTER
  66. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  67. EP260530a/AT 2026nwl: KAIT optical observations
  68. EP260602a: Optical upper limits with Kinder observations
  69. EP260602a: Einstein Probe detection of a fast X-ray transient
  70. GRB 260601B/EP260601a: SVOM/VT optical observations
  71. EP260601a: Einstein Probe detection of an X-ray transient
  72. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  73. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  74. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  75. The EP-WXT trigger 01709266272 is likely a flaring star
  76. AT2026nik: EP-FXT X-ray counterpart
  77. AT 2026nuz: COLIBRÍ optical observations
  78. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  79. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  80. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  81. EP260526a: SVOM/VT optical upper limits
  82. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  83. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  84. EP260527a/GRB 260527A: EP-FXT follow-up observation
  85. EP260526a: EP-FXT follow-up observation
  86. EP260527a: SVOM/VT optical observation
  87. EP260527a: COLIBRÍ optical detection
  88. EP260527a: Einstein Probe detection of a fast X-ray transient
  89. The EP-WXT trigger 01709266172 is likely a flaring star
  90. The EP-WXT trigger 01709266147 is likely a flaring star
  91. EP260526a: LCO optical upper limits
  92. EP260526a: Einstein Probe detection of a fast X-ray transient
  93. EP260526.405: COLIBRÍ optical upper limits
  94. The EP-WXT trigger 01709266106 is not a real source
  95. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  96. EP-WXT 01709266106: NOT optical upper limits
  97. Fermi trigger No 801135305: Global MASTER-Net observations report
  98. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  99. GRB 260511A: iTelescope T-75 optical detection
  100. GRB 260520B: SVOM/GRM observation

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