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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 260608A: Fermi GRB Observation
  2. GRB 260604C: further SAO RAS optical observations
  3. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  4. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  5. GRB 260604C: SVOM/C-GFT upper limit
  6. EP260605a: EP-FXT follow-up observation
  7. GRB 260607A: TRT optical observations
  8. GRB 260604A: SVOM/GRM detection
  9. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  10. GRB 260607B: Fermi GBM Observation
  11. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  12. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  13. GRB 260604C: 6 GHz VLA observations
  14. GRB 260604C: SAO RAS optical observations
  15. GRB 260604B: SVOM/GRM detection
  16. EP260605a: Einstein Probe detection of a fast X-ray transient
  17. EP260603a: COLIBRÍ optical upper limit
  18. GRB 260604A: Glowbug gamma-ray detection
  19. GRB 260604C: LCO optical upper limit
  20. EP260602d: EP-FXT follow-up observation
  21. EP260602c: EP-FXT follow-up observation
  22. GRB 260601B / EP260601a: AstroSat CZTI detection
  23. GRB 260527A/EP260527a: 6 GHz VLA observations
  24. GRB 260604C: Kilonova-Catcher optical afterglow detection
  25. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  26. GRB 260604C: Jinshan optical observations
  27. GRB 260604C: Fermi GBM Observation
  28. EP260602d: J-band upper limit with WINTER
  29. EP260602b: J-band upper limit with WINTER
  30. GRB 260604C: LAST detection of optical counterpart candidate
  31. Fermi GRB 260604C: Global MASTER-Net observations report
  32. Fermi GRB 260604C: Global MASTER-Net observations report
  33. SVOM GRB260604.85: Global MASTER-Net observations report
  34. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  35. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  36. EP260602a: EP-FXT follow-up observation
  37. EP260603a: Global MASTER-Net observations report
  38. EP260603a: Einstein Probe detection of a fast X-ray transient
  39. EP260602d: Optical Upper limits with kinder observations
  40. EP260602b: Liverpool Telescope observations
  41. EP260602a: Liverpool Telescope optical upper limits
  42. EP260602b: Liverpool Telescope and LCO observations
  43. EP260602a: GTC and Liverpool Telescope optical observations
  44. EP260601a/GRB 260601B: EP-FXT follow-up observation
  45. GRB 260601B / EP260601a: Mondy optical upper limit
  46. EP260602b: EP-FXT follow-up observation
  47. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  48. GRB 260603A: Kilonova-Catcher optical upper limit
  49. GRB 260603A: SVOM/VT optical observations
  50. EP260602a: NOT NIR J-band observations
  51. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  52. EP260602d: Einstein Probe detection of a fast X-ray transient
  53. Fermi trigger No 802141998: Global MASTER-Net observations report
  54. GRB 260601A: SVOM/GRM observation of a short burst
  55. EP260602c: Einstein Probe detection of a fast X-ray transient
  56. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  57. EP260602a: COLIBRÍ optical observations
  58. GRB260601B/EP260601a: NOT near-infrared observations
  59. SVOM GRB260603.23: Global MASTER-Net observations report
  60. GRB 260603A: SVOM detection of a burst
  61. EP260602b: Einstein Probe detection of a fast X-ray transient
  62. Fermi GRB 260602B: Global MASTER-Net observations report
  63. Fermi GRB 260602B: Global MASTER-Net observations report
  64. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  65. EP260602a: SVOM/VT optical candidate
  66. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  67. GRB 260601B/EP260601a: J-band upper limit with WINTER
  68. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  69. EP260530a/AT 2026nwl: KAIT optical observations
  70. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  71. EP260602a: Optical upper limits with Kinder observations
  72. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  73. EP260602a: Einstein Probe detection of a fast X-ray transient
  74. GRB 260601B/EP260601a: SVOM/VT optical observations
  75. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  76. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  77. EP260601a: Einstein Probe detection of an X-ray transient
  78. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  79. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  80. GRB 260601A: Glowbug gamma-ray detection of a short burst
  81. GRB 260531B: Glowbug gamma-ray detection
  82. GRB 260601A: Fermi GBM Observation
  83. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  84. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  85. Fermi GRB 260601A: Global MASTER-Net observations report
  86. GRB 260601A: Fermi GBM Final Real-time Localization
  87. The EP-WXT trigger 01709266272 is likely a flaring star
  88. AT2026nik: EP-FXT X-ray counterpart
  89. Fermi trigger No 801900520: Global MASTER-Net observations report
  90. GRB 260531A: MAXI/GSC detection
  91. AT 2026nuz: COLIBRÍ optical observations
  92. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  93. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  94. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  95. Fermi GRB 260529A: Global MASTER-Net observations report
  96. EP260526a: SVOM/VT optical upper limits
  97. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  98. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  99. EP260527a/GRB 260527A: EP-FXT follow-up observation
  100. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a

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