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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"

41641 results found.

  1. GRB 260703A: Fermi GBM Final Localization
  2. GRB 260610B: VLA detection
  3. GRB 260623A: Glowbug gamma-ray detection
  4. GRB 260614B: ATCA Radio Upper Limits
  5. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  6. Fermi trigger No 804552016: Global MASTER-Net observations report
  7. GRB 260701A: Fermi GBM Final Real-time Localization
  8. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  9. EP260628a: EP-FXT follow-up observation
  10. GRB 260629A: Fermi GBM Final Real-time Localization
  11. Fermi GRB 260628A: Global MASTER-Net observations report
  12. EP260628a: EP-WXT detection of a fast X-ray transient
  13. GRB 260628A: Fermi GBM Final Real-time Localization
  14. The EP-WXT trigger 01709272671 is likely a flaring star
  15. EP260626a: further Liverpool Telescope optical upper limits
  16. EP260626a: EP-FXT follow-up observation
  17. EP260626a: COLIBRÍ optical upper limit
  18. EP260626a: Liverpool Telescope upper limits
  19. EP260626a: EP-WXT detection of a fast X-ray transient
  20. Konus-Wind detection of GRB 260623B / EP260623a
  21. EP260623a: TNG NIR afterglow detection
  22. GRB 260618A: Fermi GBM Observation
  23. EP260623a: FTW optical and NIR observations
  24. GRB 260619A: SVOM/ECLAIRs refined analysis
  25. EP260623a: Liverpool Telescope optical observations
  26. Konus-Wind detection of GRB 260618B
  27. GRB 260624A: Fermi GBM Final Real-time Localization
  28. EP260623a:refined analysis of the EP-WXT and EP-FXT observation
  29. EP260623a: WINTER J-band observations
  30. GRB 260617A: Glowbug gamma-ray detection of a short burst
  31. IceCube-260622A: Upper limits from a search for additional neutrino events in IceCube
  32. EP260623a: Optical follow-up observations with Kinder
  33. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  34. GRB 260623A: Fermi GBM Final Real-time Localization
  35. EP260623a: SVOM/VT optical observations
  36. EP260623a: TRT optical observations
  37. EP260623a: REM optical/NIR afterglow detection
  38. EP 260623a: COLIBRÍ optical observations
  39. GRB 260616B/EP260616a: Insight-HXMT/HE detection
  40. EP260623a: OSIRIS+/GTC redshift z = 0.703
  41. EP260623a: Las Cumbres discovery of the optical counterpart
  42. EP260623a: Einstein Probe detection of an X-ray transient
  43. GRB 260614B: EP-FXT follow-up observation
  44. IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
  45. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  46. EP260618a: Liverpool Telescope optical observations
  47. GRB 260619A: NOT optical observations
  48. GRB 260618B: LCO optical observations
  49. The EP-WXT trigger 01709271197 is likely a flaring star
  50. EP260618a: JinShan optical observations
  51. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  52. GRB 260618B: Fermi GBM Observation
  53. IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube
  54. GRB 260619A: TRT optical counterpart confirmation
  55. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  56. GRB 260604B: 239Alferov CubeSat detection
  57. GRB 260604A: 239Alferov CubeSat detection
  58. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  59. GRB 260619A: SVOM/VT optical counterpart confirmation
  60. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  61. GRB 260618B: SVOM/VT optical candidate
  62. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  63. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  64. Konus-Wind detection of GRB 260617A
  65. GRB 260616B: AstroSat CZTI detection
  66. GRB 260616A: AstroSat CZTI detection
  67. GRB 260616A: SVOM/GRM observation
  68. EP260618a: OHP/T193 optical observations
  69. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  70. GRB 260619A: Kilonova-Catcher optical upper limit
  71. EP260618a: EP-FXT follow-up observation
  72. EP260618a: LCO optical counterpart confirmation
  73. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  74. EP260618a: COLIBRÍ optical counterpart candidate
  75. GRB 260616A: NuSTAR detection of prompt emission
  76. GRB 260614B: NuSTAR detection of prompt emission
  77. GRB 260619A: SVOM possible detection of a faint burst
  78. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  79. GRB 260618B: Fermi-LAT detection
  80. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  81. GRB 260616A: Insight-HXMT detection
  82. GRB 260618B: Fermi GBM Final Real-time Localization
  83. EP260618a: EP-WXT detection of an X-ray transient
  84. GRB 260610B: AbAO optical observations
  85. EP260616a/GRB 260616B: EP-FXT follow-up observation
  86. GRB 260506B: cubesat Avion detection
  87. GRB 260616C: GECAM-B observation of a burst
  88. GRB 260618A: Fermi GBM Final Real-time Localization
  89. GRB 260617A: Fermi GBM Detection
  90. GRB 260616A: Fermi GBM Observation
  91. GRB 260617A: Fermi GBM Final Real-time Localization
  92. Konus-Wind detection of GRB 260616B/EP260616a
  93. Konus-Wind detection of GRB 260616A
  94. GRB 260616B: CALET Gamma-Ray Burst Monitor detection
  95. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  96. GRB 260616A: GECAM-B observation
  97. GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
  98. GRB 260429A: cubesat Avion detection
  99. GRB260616C: MAXI/GSC detection
  100. GRB 260616A: Fermi-LAT detection

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