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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"

26920 results found.

  1. The EP-WXT trigger 01709274014: KAIT confirmation of a stellar flare
  2. The EP-WXT trigger 01709274014 is likely a flaring star
  3. IceCube260704A: OHP/T193 optical observations
  4. GRB 260705A: LCO optical upper limits
  5. GRB 260704A: NOT optical upper limits
  6. GRB 260705C: Fermi GBM Final Localization
  7. GRB 260705B: Fermi GBM Final Real-time Localization
  8. Fermi GBM Sub-Threshold Detection of GRB 260705A
  9. GRB 260705A: SVOM detection of a burst
  10. GRB 260704A: EP-FXT follow-up observation
  11. GRB 260629A: SVOM/GRM observation of a short burst
  12. GRB 260629A: GECAM-A observation of a short burst
  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 / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  22. Fermi trigger No 804552016: Global MASTER-Net observations report
  23. GRB 260701A: Fermi GBM Final Real-time Localization
  24. Fermi GBM trigger 804552016/260630945 is not a GRB
  25. EP260628a: EP-FXT follow-up observation
  26. GRB 260629A: Fermi GBM Final Real-time Localization
  27. Fermi GRB 260628A: Global MASTER-Net observations report
  28. EP260628a: EP-WXT detection of a fast X-ray transient
  29. GRB 260628A: Fermi GBM Final Real-time Localization
  30. The EP-WXT trigger 01709272671 is likely a flaring star
  31. EP260626a: further Liverpool Telescope optical upper limits
  32. EP260626a: EP-FXT follow-up observation
  33. EP260626a: COLIBRÍ optical upper limit
  34. EP260626a: EP-WXT detection of a fast X-ray transient
  35. EP260623a: TNG NIR afterglow detection
  36. GRB 260618A: Fermi GBM Observation
  37. EP260623a: FTW optical and NIR observations
  38. GRB 260619A: SVOM/ECLAIRs refined analysis
  39. EP260623a: Liverpool Telescope optical observations
  40. Fermi GBM trigger 804010507/260624677 is not a GRB
  41. GRB 260624A: Fermi GBM Final Real-time Localization
  42. EP260623a:refined analysis of the EP-WXT and EP-FXT observation
  43. EP260623a: WINTER J-band observations
  44. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  45. GRB 260623A: Fermi GBM Final Real-time Localization
  46. EP260623a: SVOM/VT optical observations
  47. EP260623a: TRT optical observations
  48. EP260623a: REM optical/NIR afterglow detection
  49. EP 260623a: COLIBRÍ optical observations
  50. EP260623a: OSIRIS+/GTC redshift z = 0.703
  51. EP260623a: Las Cumbres discovery of the optical counterpart
  52. EP260623a: Einstein Probe detection of an X-ray transient
  53. GRB 260614B: EP-FXT follow-up observation
  54. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  55. EP260618a: Liverpool Telescope optical observations
  56. GRB 260619A: NOT optical observations
  57. GRB 260618B: LCO optical observations
  58. The EP-WXT trigger 01709271197 is likely a flaring star
  59. EP260618a: JinShan optical observations
  60. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  61. GRB 260618B: Fermi GBM Observation
  62. GRB 260619A: TRT optical counterpart confirmation
  63. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  64. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  65. GRB 260619A: SVOM/VT optical counterpart confirmation
  66. GRB 260618B: SVOM/VT optical candidate
  67. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  68. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  69. Konus-Wind detection of GRB 260617A
  70. GRB 260616A: SVOM/GRM observation
  71. EP260618a: OHP/T193 optical observations
  72. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  73. GRB 260619A: Kilonova-Catcher optical upper limit
  74. EP260618a: EP-FXT follow-up observation
  75. EP260618a: LCO optical counterpart confirmation
  76. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  77. EP260618a: COLIBRÍ optical counterpart candidate
  78. GRB 260619A: SVOM possible detection of a faint burst
  79. GRB 260618B: Fermi-LAT detection
  80. IPN triangulation of GRB 260617A (short)
  81. GRB 260618B: Fermi GBM Final Real-time Localization
  82. EP260618a: EP-WXT detection of an X-ray transient
  83. GRB 260610B: AbAO optical observations
  84. EP260616a/GRB 260616B: EP-FXT follow-up observation
  85. GRB 260616C: GECAM-B observation of a burst
  86. GRB 260618A: Fermi GBM Final Real-time Localization
  87. GRB 260617A: Fermi GBM Detection
  88. GRB 260616A: Fermi GBM Observation
  89. GRB 260617A: Fermi GBM Final Real-time Localization
  90. GRB 260616B: CALET Gamma-Ray Burst Monitor detection
  91. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  92. GRB 260616A: GECAM-B observation
  93. GRB 260616A: Fermi-LAT detection
  94. GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
  95. GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
  96. EP260616a: EP-WXT detection of a fast X-ray transient
  97. The EP-WXT trigger 01709270148 is likely a flaring star
  98. GRB 260616B: Fermi GBM Detection
  99. GRB 260604C: GRANDMA late observations with CFHT/MegaCam
  100. GRB 260616B: BALROG localization (Fermi Trigger 803286321 / GRB 260616295)

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