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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"

27503 results found.

  1. EP260605a: COLIBRÍ optical upper limits
  2. GRB 260610b: Liverpool Telescope optical observations
  3. EP260610b: Liverpool Telescope optical upper limits
  4. The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
  5. GRB 260610B / AT2026owq: SAO RAS optical observations
  6. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  7. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  8. GRB 260610B / AT2026owq: Early ATLAS observations
  9. GRB 260610B: TRT optical observation
  10. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  11. EP260610b: COLIBRÍ optical observations
  12. GRB 260610B: DDOTI optical observations
  13. EP260610b: MAO/AZT-22 optical observations
  14. EP260610b: NOT optical observation
  15. EP260610b: SVOM/VT optical confirmation with blue color
  16. GRB 260515A: SOAR optical observations
  17. EP260610a: SVOM/VT optical upper limits
  18. EP260610b: Einstein Probe detection of an X-ray transient
  19. EP260610a: COLIBRÍ optical upper limits
  20. EP260610a: Einstein Probe detection of a fast X-ray transient
  21. GRB 260608A: Fermi GRB Observation
  22. GRB 260604C: further SAO RAS optical observations
  23. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  24. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  25. GRB 260604C: SVOM/C-GFT upper limit
  26. EP260605a: EP-FXT follow-up observation
  27. GRB 260607A: TRT optical observations
  28. GRB 260604A: SVOM/GRM detection
  29. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  30. GRB 260607B: Fermi GBM Observation
  31. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  32. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  33. GRB 260604C: 6 GHz VLA observations
  34. GRB 260604C: SAO RAS optical observations
  35. GRB 260604B: SVOM/GRM detection
  36. EP260605a: Einstein Probe detection of a fast X-ray transient
  37. EP260603a: COLIBRÍ optical upper limit
  38. GRB 260604A: Glowbug gamma-ray detection
  39. GRB 260604C: LCO optical upper limit
  40. EP260602d: EP-FXT follow-up observation
  41. EP260602c: EP-FXT follow-up observation
  42. GRB 260601B / EP260601a: AstroSat CZTI detection
  43. GRB 260527A/EP260527a: 6 GHz VLA observations
  44. GRB 260604C: Kilonova-Catcher optical afterglow detection
  45. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  46. GRB 260604C: Jinshan optical observations
  47. GRB 260604C: Fermi GBM Observation
  48. EP260602d: J-band upper limit with WINTER
  49. EP260602b: J-band upper limit with WINTER
  50. GRB 260604C: LAST detection of optical counterpart candidate
  51. Fermi GRB 260604C: Global MASTER-Net observations report
  52. Fermi GRB 260604C: Global MASTER-Net observations report
  53. SVOM GRB260604.85: Global MASTER-Net observations report
  54. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  55. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  56. EP260602a: EP-FXT follow-up observation
  57. EP260603a: Global MASTER-Net observations report
  58. EP260603a: Einstein Probe detection of a fast X-ray transient
  59. EP260602d: Optical Upper limits with kinder observations
  60. EP260602b: Liverpool Telescope observations
  61. EP260602a: Liverpool Telescope optical upper limits
  62. EP260602b: Liverpool Telescope and LCO observations
  63. EP260602a: GTC and Liverpool Telescope optical observations
  64. EP260601a/GRB 260601B: EP-FXT follow-up observation
  65. GRB 260601B / EP260601a: Mondy optical upper limit
  66. EP260602b: EP-FXT follow-up observation
  67. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  68. GRB 260603A: Kilonova-Catcher optical upper limit
  69. GRB 260603A: SVOM/VT optical observations
  70. EP260602a: NOT NIR J-band observations
  71. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  72. EP260602d: Einstein Probe detection of a fast X-ray transient
  73. Fermi trigger No 802141998: Global MASTER-Net observations report
  74. GRB 260601A: SVOM/GRM observation of a short burst
  75. EP260602c: Einstein Probe detection of a fast X-ray transient
  76. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  77. EP260602a: COLIBRÍ optical observations
  78. GRB260601B/EP260601a: NOT near-infrared observations
  79. SVOM GRB260603.23: Global MASTER-Net observations report
  80. GRB 260603A: SVOM detection of a burst
  81. EP260602b: Einstein Probe detection of a fast X-ray transient
  82. Fermi GRB 260602B: Global MASTER-Net observations report
  83. Fermi GRB 260602B: Global MASTER-Net observations report
  84. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  85. EP260602a: SVOM/VT optical candidate
  86. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  87. GRB 260601B/EP260601a: J-band upper limit with WINTER
  88. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  89. EP260530a/AT 2026nwl: KAIT optical observations
  90. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  91. EP260602a: Optical upper limits with Kinder observations
  92. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  93. EP260602a: Einstein Probe detection of a fast X-ray transient
  94. GRB 260601B/EP260601a: SVOM/VT optical observations
  95. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  96. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  97. EP260601a: Einstein Probe detection of an X-ray transient
  98. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  99. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  100. GRB 260601A: Glowbug gamma-ray detection of a short burst

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