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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"
  1. GRB 250424A: Swift-BAT refined analysis
  2. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  3. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  4. GRB 250424A: SVOM/GRM observation of a long burst
  5. GRB 250424A: PRIME near-infrared detection
  6. GRB 250424A: WINTER J-band detection
  7. GRB 250424A: EIRSAT-1 GMOD Detection
  8. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  9. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  10. GRB 250424A: SVOM/VT optical observation
  11. GRB 250419A: Mondy Optical Observations
  12. GRB 250424A: Swift/UVOT Detection
  13. Konus-Wind detection of GRB 250424A
  14. Fermi-LAT gamma-ray observations of IceCube-250421A
  15. GRB 250424A: Skynet Optical Observations
  16. GRB 250424A: Kilonova-Catcher optical afterglow detection
  17. GRB 250419a: Continued Liverpool Telescope observations
  18. GRB 250419A: Liverpool Telescope optical upper limit
  19. GRB 250407A: GRBAlpha detection
  20. GRB 250404A / EP250404a: GRBAlpha detection
  21. GRB 250330B: GRBAlpha detection
  22. GRB 250419A: SVOM/ECLAIRs refined analysis
  23. GRB 250424A: Swift-XRT refined Analysis
  24. GRB 250424A: Enhanced Swift-XRT position
  25. GRB 250424A: AstroSat CZTI detection of a bright long burst
  26. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  27. GRB 250424A: BlackGEM optical afterglow detection
  28. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  29. GRB 250424A: likely host galaxy
  30. GRB 250424A: DDOTI Afterglow Detection
  31. GRB 250424A: REM optical/NIR afterglow detection
  32. GRB 250424A: Swift detection of a burst with an optical counterpart
  33. Swift GRB 250424A: Global MASTER-Net observations report
  34. Swift GRB 250424A: Global MASTER-Net OT detection
  35. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  36. EP250421a: Nickel optical upper limit
  37. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  38. EP250421a: Upper limits from Fermi-GBM Observations
  39. SVOM/sb25042207: XRT observations
  40. SVOM/sb25042207: BOOTES-2 early optical upper limit
  41. SVOM/sb25042207: GOTO optical upper limits
  42. GRB 250421A: AstroSat CZTI detection
  43. SVOM/sb25042207: SVOM detection of an X-ray transient
  44. GRB250419A: VLA radio detection
  45. IceCube-250421A: DDOTI Detection of the LAST Candidate
  46. GRB 250419A: Mephisto Multi-band Optical Detection
  47. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  48. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  49. EP250421a: NOT optical observations
  50. GRB 250419A: Optical Observations via Virtual Telescope Project
  51. EP250421a: REM optical upper limit
  52. EP250421a: Swift/XRT counterpart detection
  53. EP250421A: COLIBRÍ Optical Upper Limit
  54. GRB 250419A: Mondy Continued Optical Observations
  55. Fermi GRB 250421A: Global MASTER-Net observations report
  56. EP250421a: Global MASTER-Net observations report
  57. GRB 250421B: AstroSat CZTI detection of a bright long burst
  58. EP250421a: Einstein Probe detection of an X-ray transient
  59. EP250421a: Mephisto optical counterpart confirmation
  60. IceCube Alert 250421.71: Global MASTER-Net observations report
  61. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  62. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  63. EP250421a: JinShan likely optical counterpart
  64. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  65. GRB 250421A: Fermi GBM Final Real-time Localization
  66. GRB 250419A: Liverpool Telescope observations
  67. GRB 250419A: LCO optical observation
  68. GRB 250419A: JinShan optical observations
  69. GRB 250419A: SVOM/VT optical continuous observations
  70. GRB 250419A: SVOM/C-GFT optical observations
  71. GRB 250419A: Swift/UVOT Follow up
  72. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  73. GRB 250419A: LCO optical afterglow multi-band observations
  74. GRB 250419A: Mondy and AbAO Optical Observations
  75. GRB 250419A: Liverpool Telescope observations
  76. GRB 250419A: AKO Optical Afterglow Detection
  77. GRB 250419A: MASTER optical afterglow observation
  78. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  79. GRB 250407A: rest-frame energetics from Konus-Wind observation
  80. GRB 250419A: Swift-XRT localisation
  81. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  82. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  83. GRB 250419A: Swift-XRT refined Analysis
  84. GRB 250419A: GOTO optical counterpart detection
  85. GRB 250419A: KAIT optical afterglow observations
  86. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  87. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  88. GRB 250419A: SVOM detection of a soft burst
  89. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  90. EP250416a: Swift/XRT counterpart fading
  91. EP250416a: refined EP-WXT and EP-FXT analysis
  92. Konus-Wind detection of GRB 250403A
  93. EP20250416a: Swift/XRT counterpart detection
  94. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  95. IceCube-250416A: DDOTI Optical Observations
  96. EP250416a: Gemini South-GMOS optical counterpart
  97. EP250225a: SVOM/VT optical brightening
  98. SVOM/sb25041603 is not a GRB
  99. EP250416a: GSP optical upper limit
  100. EP250416a: Global MASTER-Net observations report

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