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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"

28091 results found.

  1. GRB 260610B: DDOTI optical observations
  2. EP260610b: MAO/AZT-22 optical observations
  3. EP260610b: NOT optical observation
  4. EP260610b: SVOM/VT optical confirmation with blue color
  5. GRB 260515A: SOAR optical observations
  6. EP260610a: SVOM/VT optical upper limits
  7. EP260610b: Einstein Probe detection of an X-ray transient
  8. EP260610a: COLIBRÍ optical upper limits
  9. EP260610a: Einstein Probe detection of a fast X-ray transient
  10. GRB 260608A: Fermi GRB Observation
  11. GRB 260604C: further SAO RAS optical observations
  12. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  13. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  14. GRB 260604C: SVOM/C-GFT upper limit
  15. EP260605a: EP-FXT follow-up observation
  16. GRB 260607A: TRT optical observations
  17. GRB 260604A: SVOM/GRM detection
  18. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  19. GRB 260607B: Fermi GBM Observation
  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 260604A: Glowbug gamma-ray detection
  28. GRB 260604C: LCO optical upper limit
  29. EP260602d: EP-FXT follow-up observation
  30. EP260602c: EP-FXT follow-up observation
  31. GRB 260601B / EP260601a: AstroSat CZTI detection
  32. GRB 260527A/EP260527a: 6 GHz VLA observations
  33. GRB 260604C: Kilonova-Catcher optical afterglow detection
  34. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  35. GRB 260604C: Jinshan optical observations
  36. GRB 260604C: Fermi GBM Observation
  37. EP260602d: J-band upper limit with WINTER
  38. EP260602b: J-band upper limit with WINTER
  39. GRB 260604C: LAST detection of optical counterpart candidate
  40. Fermi GRB 260604C: Global MASTER-Net observations report
  41. Fermi GRB 260604C: Global MASTER-Net observations report
  42. SVOM GRB260604.85: Global MASTER-Net observations report
  43. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  44. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  45. EP260602a: EP-FXT follow-up observation
  46. EP260603a: Global MASTER-Net observations report
  47. EP260603a: Einstein Probe detection of a fast X-ray transient
  48. EP260602d: Optical Upper limits with kinder observations
  49. EP260602b: Liverpool Telescope observations
  50. EP260602a: Liverpool Telescope optical upper limits
  51. EP260602b: Liverpool Telescope and LCO observations
  52. EP260602a: GTC and Liverpool Telescope optical observations
  53. EP260601a/GRB 260601B: EP-FXT follow-up observation
  54. GRB 260601B / EP260601a: Mondy optical upper limit
  55. EP260602b: EP-FXT follow-up observation
  56. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  57. GRB 260603A: Kilonova-Catcher optical upper limit
  58. GRB 260603A: SVOM/VT optical observations
  59. EP260602a: NOT NIR J-band observations
  60. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  61. EP260602d: Einstein Probe detection of a fast X-ray transient
  62. Fermi trigger No 802141998: Global MASTER-Net observations report
  63. GRB 260601A: SVOM/GRM observation of a short burst
  64. EP260602c: Einstein Probe detection of a fast X-ray transient
  65. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  66. EP260602a: COLIBRÍ optical observations
  67. GRB260601B/EP260601a: NOT near-infrared observations
  68. SVOM GRB260603.23: Global MASTER-Net observations report
  69. GRB 260603A: SVOM detection of a burst
  70. EP260602b: Einstein Probe detection of a fast X-ray transient
  71. Fermi GRB 260602B: Global MASTER-Net observations report
  72. Fermi GRB 260602B: Global MASTER-Net observations report
  73. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  74. EP260602a: SVOM/VT optical candidate
  75. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  76. GRB 260601B/EP260601a: J-band upper limit with WINTER
  77. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  78. EP260530a/AT 2026nwl: KAIT optical observations
  79. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  80. EP260602a: Optical upper limits with Kinder observations
  81. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  82. EP260602a: Einstein Probe detection of a fast X-ray transient
  83. GRB 260601B/EP260601a: SVOM/VT optical observations
  84. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  85. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  86. EP260601a: Einstein Probe detection of an X-ray transient
  87. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  88. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  89. GRB 260601A: Glowbug gamma-ray detection of a short burst
  90. GRB 260531B: Glowbug gamma-ray detection
  91. GRB 260601A: Fermi GBM Observation
  92. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  93. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  94. Fermi GRB 260601A: Global MASTER-Net observations report
  95. GRB 260601A: Fermi GBM Final Real-time Localization
  96. The EP-WXT trigger 01709266272 is likely a flaring star
  97. AT2026nik: EP-FXT X-ray counterpart
  98. Fermi trigger No 801900520: Global MASTER-Net observations report
  99. GRB 260531A: MAXI/GSC detection
  100. AT 2026nuz: COLIBRÍ optical observations

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