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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"

27873 results found.

  1. Fermi GRB 260628A: Global MASTER-Net observations report
  2. EP260628a: EP-WXT detection of a fast X-ray transient
  3. EP260626a: further Liverpool Telescope optical upper limits
  4. EP260626a: COLIBRÍ optical upper limit
  5. EP260626a: Liverpool Telescope upper limits
  6. EP260626a: EP-WXT detection of a fast X-ray transient
  7. EP260623a: TNG NIR afterglow detection
  8. GRB 260618A: Fermi GBM Observation
  9. GRB 260619A: SVOM/ECLAIRs refined analysis
  10. EP260623a: Liverpool Telescope optical observations
  11. EP260623a:refined analysis of the EP-WXT and EP-FXT observation
  12. EP260623a: WINTER J-band observations
  13. GRB 260617A: Glowbug gamma-ray detection of a short burst
  14. IceCube-260622A: Upper limits from a search for additional neutrino events in IceCube
  15. EP260623a: Optical follow-up observations with Kinder
  16. EP260623a: SVOM/VT optical observations
  17. EP260623a: TRT optical observations
  18. EP260623a: REM optical/NIR afterglow detection
  19. EP 260623a: COLIBRÍ optical observations
  20. GRB 260616B/EP260616a: Insight-HXMT/HE detection
  21. EP260623a: Las Cumbres discovery of the optical counterpart
  22. EP260623a: Einstein Probe detection of an X-ray transient
  23. GRB 260614B: EP-FXT follow-up observation
  24. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  25. EP260618a: Liverpool Telescope optical observations
  26. GRB 260618B: LCO optical observations
  27. EP260618a: JinShan optical observations
  28. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  29. GRB 260618B: Fermi GBM Observation
  30. IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube
  31. GRB 260619A: TRT optical counterpart confirmation
  32. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  33. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  34. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  35. GRB 260616B: AstroSat CZTI detection
  36. GRB 260616A: AstroSat CZTI detection
  37. GRB 260616A: SVOM/GRM observation
  38. EP260618a: OHP/T193 optical observations
  39. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  40. GRB 260619A: Kilonova-Catcher optical upper limit
  41. EP260618a: LCO optical counterpart confirmation
  42. EP260618a: COLIBRÍ optical counterpart candidate
  43. GRB 260616A: NuSTAR detection of prompt emission
  44. GRB 260614B: NuSTAR detection of prompt emission
  45. GRB 260619A: SVOM possible detection of a faint burst
  46. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  47. EP260618a: EP-WXT detection of an X-ray transient
  48. GRB 260610B: AbAO optical observations
  49. GRB 260506B: cubesat Avion detection
  50. GRB 260617A: Fermi GBM Detection
  51. GRB 260616A: Fermi GBM Observation
  52. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  53. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  54. GRB 260429A: cubesat Avion detection
  55. GRB260616C: MAXI/GSC detection
  56. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  57. EP260616a: EP-WXT detection of a fast X-ray transient
  58. GRB 260616B: Fermi GBM Detection
  59. GRB 260616B: BALROG localization (Fermi Trigger 803286321 / GRB 260616295)
  60. GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140)
  61. GRB 260610B: Terskol optical observations
  62. GRB 260610B: SVOM/GRM observation
  63. GRB 260614B: Fermi GBM Observation
  64. GRB 260614B: SVOM/VT optical candidate from VHF data
  65. GRB 260614B: SVOM detection of a burst
  66. GRB 260611B: SVOM/GRM detection
  67. The EP-WXT trigger 01709269488 is likely a flaring star
  68. GRB 260610B: further Liverpool Telescope optical observations
  69. GRB 260610B: Fermi GBM Observation
  70. GRB 260610B / AT2026owq: GRANDMA optical observations
  71. GRB 260610B / AT2026owq: further SAO RAS optical observations
  72. EP260605a: COLIBRÍ optical upper limits
  73. GRB 260610b: Liverpool Telescope optical observations
  74. EP260610b: Liverpool Telescope optical upper limits
  75. The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
  76. GRB 260610B / AT2026owq: SAO RAS optical observations
  77. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  78. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  79. GRB 260610B / AT2026owq: Early ATLAS observations
  80. GRB 260610B: TRT optical observation
  81. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  82. EP260610b: COLIBRÍ optical observations
  83. GRB 260610B: DDOTI optical observations
  84. EP260610b: MAO/AZT-22 optical observations
  85. EP260610b: NOT optical observation
  86. EP260610b: SVOM/VT optical confirmation with blue color
  87. GRB 260515A: SOAR optical observations
  88. EP260610a: SVOM/VT optical upper limits
  89. EP260610b: Einstein Probe detection of an X-ray transient
  90. EP260610a: COLIBRÍ optical upper limits
  91. EP260610a: Einstein Probe detection of a fast X-ray transient
  92. GRB 260608A: Fermi GRB Observation
  93. GRB 260604C: further SAO RAS optical observations
  94. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  95. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  96. GRB 260604C: SVOM/C-GFT upper limit
  97. EP260605a: EP-FXT follow-up observation
  98. GRB 260607A: TRT optical observations
  99. GRB 260604A: SVOM/GRM detection
  100. GRB 260604C: Mondy optical observations: evidence of a possible brightening

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