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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"

28082 results found.

  1. GRB 260604C: further SAO RAS optical observations
  2. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  3. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  4. GRB 260604C: SVOM/C-GFT upper limit
  5. EP260605a: EP-FXT follow-up observation
  6. GRB 260607A: TRT optical observations
  7. GRB 260604A: SVOM/GRM detection
  8. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  9. GRB 260607B: Fermi GBM Observation
  10. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  11. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  12. GRB 260604C: 6 GHz VLA observations
  13. GRB 260604C: SAO RAS optical observations
  14. GRB 260604B: SVOM/GRM detection
  15. EP260605a: Einstein Probe detection of a fast X-ray transient
  16. EP260603a: COLIBRÍ optical upper limit
  17. GRB 260604A: Glowbug gamma-ray detection
  18. GRB 260604C: LCO optical upper limit
  19. EP260602d: EP-FXT follow-up observation
  20. EP260602c: EP-FXT follow-up observation
  21. GRB 260601B / EP260601a: AstroSat CZTI detection
  22. GRB 260527A/EP260527a: 6 GHz VLA observations
  23. GRB 260604C: Kilonova-Catcher optical afterglow detection
  24. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  25. GRB 260604C: Jinshan optical observations
  26. GRB 260604C: Fermi GBM Observation
  27. EP260602d: J-band upper limit with WINTER
  28. EP260602b: J-band upper limit with WINTER
  29. GRB 260604C: LAST detection of optical counterpart candidate
  30. Fermi GRB 260604C: Global MASTER-Net observations report
  31. Fermi GRB 260604C: Global MASTER-Net observations report
  32. SVOM GRB260604.85: Global MASTER-Net observations report
  33. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  34. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  35. EP260602a: EP-FXT follow-up observation
  36. EP260603a: Global MASTER-Net observations report
  37. EP260603a: Einstein Probe detection of a fast X-ray transient
  38. EP260602d: Optical Upper limits with kinder observations
  39. EP260602b: Liverpool Telescope observations
  40. EP260602a: Liverpool Telescope optical upper limits
  41. EP260602b: Liverpool Telescope and LCO observations
  42. EP260602a: GTC and Liverpool Telescope optical observations
  43. EP260601a/GRB 260601B: EP-FXT follow-up observation
  44. GRB 260601B / EP260601a: Mondy optical upper limit
  45. EP260602b: EP-FXT follow-up observation
  46. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  47. GRB 260603A: Kilonova-Catcher optical upper limit
  48. GRB 260603A: SVOM/VT optical observations
  49. EP260602a: NOT NIR J-band observations
  50. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  51. EP260602d: Einstein Probe detection of a fast X-ray transient
  52. Fermi trigger No 802141998: Global MASTER-Net observations report
  53. GRB 260601A: SVOM/GRM observation of a short burst
  54. EP260602c: Einstein Probe detection of a fast X-ray transient
  55. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  56. EP260602a: COLIBRÍ optical observations
  57. GRB260601B/EP260601a: NOT near-infrared observations
  58. SVOM GRB260603.23: Global MASTER-Net observations report
  59. GRB 260603A: SVOM detection of a burst
  60. EP260602b: Einstein Probe detection of a fast X-ray transient
  61. Fermi GRB 260602B: Global MASTER-Net observations report
  62. Fermi GRB 260602B: Global MASTER-Net observations report
  63. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  64. EP260602a: SVOM/VT optical candidate
  65. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  66. GRB 260601B/EP260601a: J-band upper limit with WINTER
  67. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  68. EP260530a/AT 2026nwl: KAIT optical observations
  69. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  70. EP260602a: Optical upper limits with Kinder observations
  71. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  72. EP260602a: Einstein Probe detection of a fast X-ray transient
  73. GRB 260601B/EP260601a: SVOM/VT optical observations
  74. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  75. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  76. EP260601a: Einstein Probe detection of an X-ray transient
  77. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  78. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  79. GRB 260601A: Glowbug gamma-ray detection of a short burst
  80. GRB 260531B: Glowbug gamma-ray detection
  81. GRB 260601A: Fermi GBM Observation
  82. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  83. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  84. Fermi GRB 260601A: Global MASTER-Net observations report
  85. GRB 260601A: Fermi GBM Final Real-time Localization
  86. The EP-WXT trigger 01709266272 is likely a flaring star
  87. AT2026nik: EP-FXT X-ray counterpart
  88. Fermi trigger No 801900520: Global MASTER-Net observations report
  89. GRB 260531A: MAXI/GSC detection
  90. AT 2026nuz: COLIBRÍ optical observations
  91. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  92. GRB 260429B / EP260429a: COLIBRÍ optical counterpart 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. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  97. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  98. EP260527a/GRB 260527A: EP-FXT follow-up observation
  99. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  100. EP260527a: SVOM/VT optical observation

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