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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"

28045 results found.

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

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