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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"

28057 results found.

  1. EP 260623a: COLIBRÍ optical observations
  2. GRB 260616B/EP260616a: Insight-HXMT/HE detection
  3. EP260623a: Las Cumbres discovery of the optical counterpart
  4. EP260623a: Einstein Probe detection of an X-ray transient
  5. GRB 260614B: EP-FXT follow-up observation
  6. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  7. EP260618a: Liverpool Telescope optical observations
  8. GRB 260618B: LCO optical observations
  9. EP260618a: JinShan optical observations
  10. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  11. GRB 260618B: Fermi GBM Observation
  12. IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube
  13. GRB 260619A: TRT optical counterpart confirmation
  14. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  15. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  16. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  17. GRB 260616B: AstroSat CZTI detection
  18. GRB 260616A: AstroSat CZTI detection
  19. GRB 260616A: SVOM/GRM observation
  20. EP260618a: OHP/T193 optical observations
  21. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  22. GRB 260619A: Kilonova-Catcher optical upper limit
  23. EP260618a: LCO optical counterpart confirmation
  24. EP260618a: COLIBRÍ optical counterpart candidate
  25. GRB 260616A: NuSTAR detection of prompt emission
  26. GRB 260614B: NuSTAR detection of prompt emission
  27. GRB 260619A: SVOM possible detection of a faint burst
  28. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  29. EP260618a: EP-WXT detection of an X-ray transient
  30. GRB 260610B: AbAO optical observations
  31. GRB 260506B: cubesat Avion detection
  32. GRB 260617A: Fermi GBM Detection
  33. GRB 260616A: Fermi GBM Observation
  34. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  35. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  36. GRB 260429A: cubesat Avion detection
  37. GRB260616C: MAXI/GSC detection
  38. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  39. EP260616a: EP-WXT detection of a fast X-ray transient
  40. GRB 260616B: Fermi GBM Detection
  41. GRB 260616B: BALROG localization (Fermi Trigger 803286321 / GRB 260616295)
  42. GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140)
  43. GRB 260610B: Terskol optical observations
  44. GRB 260610B: SVOM/GRM observation
  45. GRB 260614B: Fermi GBM Observation
  46. GRB 260614B: SVOM/VT optical candidate from VHF data
  47. GRB 260614B: SVOM detection of a burst
  48. GRB 260611B: SVOM/GRM detection
  49. The EP-WXT trigger 01709269488 is likely a flaring star
  50. GRB 260610B: further Liverpool Telescope optical observations
  51. GRB 260610B: Fermi GBM Observation
  52. GRB 260610B / AT2026owq: GRANDMA optical observations
  53. GRB 260610B / AT2026owq: further SAO RAS optical observations
  54. EP260605a: COLIBRÍ optical upper limits
  55. GRB 260610b: Liverpool Telescope optical observations
  56. EP260610b: Liverpool Telescope optical upper limits
  57. The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
  58. GRB 260610B / AT2026owq: SAO RAS optical observations
  59. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  60. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  61. GRB 260610B / AT2026owq: Early ATLAS observations
  62. GRB 260610B: TRT optical observation
  63. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  64. EP260610b: COLIBRÍ optical observations
  65. GRB 260610B: DDOTI optical observations
  66. EP260610b: MAO/AZT-22 optical observations
  67. EP260610b: NOT optical observation
  68. EP260610b: SVOM/VT optical confirmation with blue color
  69. GRB 260515A: SOAR optical observations
  70. EP260610a: SVOM/VT optical upper limits
  71. EP260610b: Einstein Probe detection of an X-ray transient
  72. EP260610a: COLIBRÍ optical upper limits
  73. EP260610a: Einstein Probe detection of a fast X-ray transient
  74. GRB 260608A: Fermi GRB Observation
  75. GRB 260604C: further SAO RAS optical observations
  76. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  77. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  78. GRB 260604C: SVOM/C-GFT upper limit
  79. EP260605a: EP-FXT follow-up observation
  80. GRB 260607A: TRT optical observations
  81. GRB 260604A: SVOM/GRM detection
  82. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  83. GRB 260607B: Fermi GBM Observation
  84. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  85. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  86. GRB 260604C: 6 GHz VLA observations
  87. GRB 260604C: SAO RAS optical observations
  88. GRB 260604B: SVOM/GRM detection
  89. EP260605a: Einstein Probe detection of a fast X-ray transient
  90. EP260603a: COLIBRÍ optical upper limit
  91. GRB 260604A: Glowbug gamma-ray detection
  92. GRB 260604C: LCO optical upper limit
  93. EP260602d: EP-FXT follow-up observation
  94. EP260602c: EP-FXT follow-up observation
  95. GRB 260601B / EP260601a: AstroSat CZTI detection
  96. GRB 260527A/EP260527a: 6 GHz VLA observations
  97. GRB 260604C: Kilonova-Catcher optical afterglow detection
  98. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  99. GRB 260604C: Jinshan optical observations
  100. GRB 260604C: Fermi GBM Observation

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