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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"

43616 results found.

  1. GRB 260629A: AstroSat CZTI detection
  2. EP260703a: EP-FXT follow-up observation
  3. GRB 260704A: SVOM detection of a possible GRB
  4. GRB 260703B: Fermi GBM Final Localization
  5. EP260703a: EP-WXT detection of a fast X-ray transient
  6. EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
  7. Fermi trigger No 804738310: Global MASTER-Net observations report
  8. Fermi GRB 260703A: Global MASTER-Net observations report
  9. GRB 260703A: Fermi GBM Final Localization
  10. GRB 260610B: VLA detection
  11. GRB 260623A: Glowbug gamma-ray detection
  12. GRB 260614B: ATCA Radio Upper Limits
  13. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  14. Fermi trigger No 804552016: Global MASTER-Net observations report
  15. GRB 260701A: Fermi GBM Final Real-time Localization
  16. Fermi GBM trigger 804552016/260630945 is not a GRB
  17. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  18. EP260628a: EP-FXT follow-up observation
  19. GRB 260629A: Fermi GBM Final Real-time Localization
  20. Fermi GRB 260628A: Global MASTER-Net observations report
  21. EP260628a: EP-WXT detection of a fast X-ray transient
  22. GRB 260628A: Fermi GBM Final Real-time Localization
  23. The EP-WXT trigger 01709272671 is likely a flaring star
  24. EP260626a: further Liverpool Telescope optical upper limits
  25. EP260626a: EP-FXT follow-up observation
  26. EP260626a: COLIBRÍ optical upper limit
  27. EP260626a: Liverpool Telescope upper limits
  28. EP260626a: EP-WXT detection of a fast X-ray transient
  29. Konus-Wind detection of GRB 260623B / EP260623a
  30. EP260623a: TNG NIR afterglow detection
  31. GRB 260618A: Fermi GBM Observation
  32. MASS-Cube (GRID 2.0) detection of GRB 260616B
  33. EP260623a: FTW optical and NIR observations
  34. GRB 260619A: SVOM/ECLAIRs refined analysis
  35. EP260623a: Liverpool Telescope optical observations
  36. Fermi GBM trigger 804010507/260624677 is not a GRB
  37. Konus-Wind detection of GRB 260618B
  38. GRB 260624A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  39. GRB 260624A: Fermi GBM Final Real-time Localization
  40. EP260623a:refined analysis of the EP-WXT and EP-FXT observation
  41. EP260623a: WINTER J-band observations
  42. GRB 260617A: Glowbug gamma-ray detection of a short burst
  43. IceCube-260622A: Upper limits from a search for additional neutrino events in IceCube
  44. IPN triangulation of GRB 260605A
  45. EP260623a: Optical follow-up observations with Kinder
  46. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  47. GRB 260623A: Fermi GBM Final Real-time Localization
  48. EP260623a: SVOM/VT optical observations
  49. EP260623a: TRT optical observations
  50. EP260623a: REM optical/NIR afterglow detection
  51. EP 260623a: COLIBRÍ optical observations
  52. GRB 260616B/EP260616a: Insight-HXMT/HE detection
  53. EP260623a: OSIRIS+/GTC redshift z = 0.703
  54. EP260623a: Las Cumbres discovery of the optical counterpart
  55. EP260623a: Einstein Probe detection of an X-ray transient
  56. GRB 260614B: EP-FXT follow-up observation
  57. IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
  58. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  59. EP260618a: Liverpool Telescope optical observations
  60. GRB 260619A: NOT optical observations
  61. GRB 260618B: LCO optical observations
  62. The EP-WXT trigger 01709271197 is likely a flaring star
  63. EP260618a: JinShan optical observations
  64. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  65. GRB 260618B: Fermi GBM Observation
  66. IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube
  67. GRB 260619A: TRT optical counterpart confirmation
  68. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  69. GRB 260604B: 239Alferov CubeSat detection
  70. GRB 260604A: 239Alferov CubeSat detection
  71. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  72. GRB 260619A: SVOM/VT optical counterpart confirmation
  73. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  74. GRB 260618B: SVOM/VT optical candidate
  75. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  76. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  77. Konus-Wind detection of GRB 260617A
  78. GRB 260616B: AstroSat CZTI detection
  79. GRB 260616A: AstroSat CZTI detection
  80. GRB 260616A: SVOM/GRM observation
  81. EP260618a: OHP/T193 optical observations
  82. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  83. GRB 260619A: Kilonova-Catcher optical upper limit
  84. EP260618a: EP-FXT follow-up observation
  85. EP260618a: LCO optical counterpart confirmation
  86. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  87. EP260618a: COLIBRÍ optical counterpart candidate
  88. GRB 260616A: NuSTAR detection of prompt emission
  89. GRB 260614B: NuSTAR detection of prompt emission
  90. GRB 260619A: SVOM possible detection of a faint burst
  91. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  92. GRB 260618B: Fermi-LAT detection
  93. IPN triangulation of GRB 260617A (short)
  94. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  95. GRB 260616A: Insight-HXMT detection
  96. GRB 260618B: Fermi GBM Final Real-time Localization
  97. EP260618a: EP-WXT detection of an X-ray transient
  98. GRB 260610B: AbAO optical observations
  99. EP260616a/GRB 260616B: EP-FXT follow-up observation
  100. GRB 260506B: cubesat Avion detection

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