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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"

45463 results found.

  1. IceCube260704A: OHP/T193 optical observations
  2. GRB 260705A: LCO optical upper limits
  3. GRB 260704A: NOT optical upper limits
  4. GRB 260705C: Fermi GBM Final Localization
  5. GRB 260705B: Fermi GBM Final Real-time Localization
  6. Fermi GBM Sub-Threshold Detection of GRB 260705A
  7. GRB 260705A: SVOM detection of a burst
  8. GRB 260704A: EP-FXT follow-up observation
  9. GRB 260629A: SVOM/GRM observation of a short burst
  10. GRB 260629A: GECAM-A observation of a short burst
  11. IceCube-260704A - IceCube observation of a high-energy neutrino candidate track-like event
  12. GRB 260629A: AstroSat CZTI detection
  13. EP260703a: EP-FXT follow-up observation
  14. GRB 260704A: SVOM detection of a possible GRB
  15. GRB 260703B: Fermi GBM Final Localization
  16. EP260703a: EP-WXT detection of a fast X-ray transient
  17. EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
  18. Fermi trigger No 804738310: Global MASTER-Net observations report
  19. Fermi GRB 260703A: Global MASTER-Net observations report
  20. GRB 260703A: Fermi GBM Final Localization
  21. GRB 260610B: VLA detection
  22. GRB 260623A: Glowbug gamma-ray detection
  23. GRB 260614B: ATCA Radio Upper Limits
  24. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  25. Fermi trigger No 804552016: Global MASTER-Net observations report
  26. GRB 260701A: Fermi GBM Final Real-time Localization
  27. Fermi GBM trigger 804552016/260630945 is not a GRB
  28. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  29. EP260628a: EP-FXT follow-up observation
  30. GRB 260629A: Fermi GBM Final Real-time Localization
  31. Fermi GRB 260628A: Global MASTER-Net observations report
  32. EP260628a: EP-WXT detection of a fast X-ray transient
  33. GRB 260628A: Fermi GBM Final Real-time Localization
  34. The EP-WXT trigger 01709272671 is likely a flaring star
  35. EP260626a: further Liverpool Telescope optical upper limits
  36. EP260626a: EP-FXT follow-up observation
  37. EP260626a: COLIBRÍ optical upper limit
  38. EP260626a: Liverpool Telescope upper limits
  39. EP260626a: EP-WXT detection of a fast X-ray transient
  40. Konus-Wind detection of GRB 260623B / EP260623a
  41. EP260623a: TNG NIR afterglow detection
  42. GRB 260618A: Fermi GBM Observation
  43. MASS-Cube (GRID 2.0) detection of GRB 260616B
  44. EP260623a: FTW optical and NIR observations
  45. GRB 260619A: SVOM/ECLAIRs refined analysis
  46. EP260623a: Liverpool Telescope optical observations
  47. Fermi GBM trigger 804010507/260624677 is not a GRB
  48. Konus-Wind detection of GRB 260618B
  49. GRB 260624A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  50. GRB 260624A: Fermi GBM Final Real-time Localization
  51. EP260623a:refined analysis of the EP-WXT and EP-FXT observation
  52. EP260623a: WINTER J-band observations
  53. GRB 260617A: Glowbug gamma-ray detection of a short burst
  54. IceCube-260622A: Upper limits from a search for additional neutrino events in IceCube
  55. IPN triangulation of GRB 260605A
  56. EP260623a: Optical follow-up observations with Kinder
  57. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  58. GRB 260623A: Fermi GBM Final Real-time Localization
  59. EP260623a: SVOM/VT optical observations
  60. EP260623a: TRT optical observations
  61. EP260623a: REM optical/NIR afterglow detection
  62. EP 260623a: COLIBRÍ optical observations
  63. GRB 260616B/EP260616a: Insight-HXMT/HE detection
  64. EP260623a: OSIRIS+/GTC redshift z = 0.703
  65. EP260623a: Las Cumbres discovery of the optical counterpart
  66. EP260623a: Einstein Probe detection of an X-ray transient
  67. GRB 260614B: EP-FXT follow-up observation
  68. IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
  69. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  70. EP260618a: Liverpool Telescope optical observations
  71. GRB 260619A: NOT optical observations
  72. GRB 260618B: LCO optical observations
  73. The EP-WXT trigger 01709271197 is likely a flaring star
  74. EP260618a: JinShan optical observations
  75. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  76. GRB 260618B: Fermi GBM Observation
  77. IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube
  78. GRB 260619A: TRT optical counterpart confirmation
  79. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  80. GRB 260604B: 239Alferov CubeSat detection
  81. GRB 260604A: 239Alferov CubeSat detection
  82. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  83. GRB 260619A: SVOM/VT optical counterpart confirmation
  84. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  85. GRB 260618B: SVOM/VT optical candidate
  86. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  87. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  88. Konus-Wind detection of GRB 260617A
  89. GRB 260616B: AstroSat CZTI detection
  90. GRB 260616A: AstroSat CZTI detection
  91. GRB 260616A: SVOM/GRM observation
  92. EP260618a: OHP/T193 optical observations
  93. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  94. GRB 260619A: Kilonova-Catcher optical upper limit
  95. EP260618a: EP-FXT follow-up observation
  96. EP260618a: LCO optical counterpart confirmation
  97. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  98. EP260618a: COLIBRÍ optical counterpart candidate
  99. GRB 260616A: NuSTAR detection of prompt emission
  100. GRB 260614B: NuSTAR detection of prompt emission

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