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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"

28038 results found.

  1. EP260618a: OHP/T193 optical observations
  2. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  3. GRB 260619A: Kilonova-Catcher optical upper limit
  4. EP260618a: LCO optical counterpart confirmation
  5. EP260618a: COLIBRÍ optical counterpart candidate
  6. GRB 260616A: NuSTAR detection of prompt emission
  7. GRB 260614B: NuSTAR detection of prompt emission
  8. GRB 260619A: SVOM possible detection of a faint burst
  9. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  10. EP260618a: EP-WXT detection of an X-ray transient
  11. GRB 260610B: AbAO optical observations
  12. GRB 260506B: cubesat Avion detection
  13. GRB 260617A: Fermi GBM Detection
  14. GRB 260616A: Fermi GBM Observation
  15. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  16. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  17. GRB 260429A: cubesat Avion detection
  18. GRB260616C: MAXI/GSC detection
  19. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  20. EP260616a: EP-WXT detection of a fast X-ray transient
  21. GRB 260616B: Fermi GBM Detection
  22. GRB 260616B: BALROG localization (Fermi Trigger 803286321 / GRB 260616295)
  23. GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140)
  24. GRB 260610B: Terskol optical observations
  25. GRB 260610B: SVOM/GRM observation
  26. GRB 260614B: Fermi GBM Observation
  27. GRB 260614B: SVOM/VT optical candidate from VHF data
  28. GRB 260614B: SVOM detection of a burst
  29. GRB 260611B: SVOM/GRM detection
  30. The EP-WXT trigger 01709269488 is likely a flaring star
  31. GRB 260610B: further Liverpool Telescope optical observations
  32. GRB 260610B: Fermi GBM Observation
  33. GRB 260610B / AT2026owq: GRANDMA optical observations
  34. GRB 260610B / AT2026owq: further SAO RAS optical observations
  35. EP260605a: COLIBRÍ optical upper limits
  36. GRB 260610b: Liverpool Telescope optical observations
  37. EP260610b: Liverpool Telescope optical upper limits
  38. The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
  39. GRB 260610B / AT2026owq: SAO RAS optical observations
  40. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  41. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  42. GRB 260610B / AT2026owq: Early ATLAS observations
  43. GRB 260610B: TRT optical observation
  44. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  45. EP260610b: COLIBRÍ optical observations
  46. GRB 260610B: DDOTI optical observations
  47. EP260610b: MAO/AZT-22 optical observations
  48. EP260610b: NOT optical observation
  49. EP260610b: SVOM/VT optical confirmation with blue color
  50. GRB 260515A: SOAR optical observations
  51. EP260610a: SVOM/VT optical upper limits
  52. EP260610b: Einstein Probe detection of an X-ray transient
  53. EP260610a: COLIBRÍ optical upper limits
  54. EP260610a: Einstein Probe detection of a fast X-ray transient
  55. GRB 260608A: Fermi GRB Observation
  56. GRB 260604C: further SAO RAS optical observations
  57. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  58. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  59. GRB 260604C: SVOM/C-GFT upper limit
  60. EP260605a: EP-FXT follow-up observation
  61. GRB 260607A: TRT optical observations
  62. GRB 260604A: SVOM/GRM detection
  63. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  64. GRB 260607B: Fermi GBM Observation
  65. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  66. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  67. GRB 260604C: 6 GHz VLA observations
  68. GRB 260604C: SAO RAS optical observations
  69. GRB 260604B: SVOM/GRM detection
  70. EP260605a: Einstein Probe detection of a fast X-ray transient
  71. EP260603a: COLIBRÍ optical upper limit
  72. GRB 260604A: Glowbug gamma-ray detection
  73. GRB 260604C: LCO optical upper limit
  74. EP260602d: EP-FXT follow-up observation
  75. EP260602c: EP-FXT follow-up observation
  76. GRB 260601B / EP260601a: AstroSat CZTI detection
  77. GRB 260527A/EP260527a: 6 GHz VLA observations
  78. GRB 260604C: Kilonova-Catcher optical afterglow detection
  79. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  80. GRB 260604C: Jinshan optical observations
  81. GRB 260604C: Fermi GBM Observation
  82. EP260602d: J-band upper limit with WINTER
  83. EP260602b: J-band upper limit with WINTER
  84. GRB 260604C: LAST detection of optical counterpart candidate
  85. Fermi GRB 260604C: Global MASTER-Net observations report
  86. Fermi GRB 260604C: Global MASTER-Net observations report
  87. SVOM GRB260604.85: Global MASTER-Net observations report
  88. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  89. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  90. EP260602a: EP-FXT follow-up observation
  91. EP260603a: Global MASTER-Net observations report
  92. EP260603a: Einstein Probe detection of a fast X-ray transient
  93. EP260602d: Optical Upper limits with kinder observations
  94. EP260602b: Liverpool Telescope observations
  95. EP260602a: Liverpool Telescope optical upper limits
  96. EP260602b: Liverpool Telescope and LCO observations
  97. EP260602a: GTC and Liverpool Telescope optical observations
  98. EP260601a/GRB 260601B: EP-FXT follow-up observation
  99. GRB 260601B / EP260601a: Mondy optical upper limit
  100. EP260602b: EP-FXT follow-up observation

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