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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. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  2. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event
  3. GRB 250424A: SVOM/GRM observation of a long burst
  4. GRB 250424A: PRIME near-infrared detection
  5. GRB 250424A: WINTER J-band detection
  6. GRB 250424A: EIRSAT-1 GMOD Detection
  7. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  8. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  9. GRB 250424A: SVOM/VT optical observation
  10. GRB 250419A: Mondy Optical Observations
  11. GRB 250424A: Swift/UVOT Detection
  12. Konus-Wind detection of GRB 250424A
  13. Fermi-LAT gamma-ray observations of IceCube-250421A
  14. GRB 250424A: Skynet Optical Observations
  15. GRB 250424A: Kilonova-Catcher optical afterglow detection
  16. GRB 250419a: Continued Liverpool Telescope observations
  17. GRB 250419A: Liverpool Telescope optical upper limit
  18. GRB 250407A: GRBAlpha detection
  19. GRB 250404A / EP250404a: GRBAlpha detection
  20. GRB 250330B: GRBAlpha detection
  21. GRB 250419A: SVOM/ECLAIRs refined analysis
  22. GRB 250424A: Swift-XRT refined Analysis
  23. GRB 250424A: Enhanced Swift-XRT position
  24. GRB 250424A: AstroSat CZTI detection of a bright long burst
  25. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  26. GRB 250424A: BlackGEM optical afterglow detection
  27. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  28. GRB 250424A: likely host galaxy
  29. GRB 250424A: DDOTI Afterglow Detection
  30. GRB 250424A: REM optical/NIR afterglow detection
  31. GRB 250424A: Swift detection of a burst with an optical counterpart
  32. Swift GRB 250424A: Global MASTER-Net observations report
  33. Swift GRB 250424A: Global MASTER-Net OT detection
  34. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  35. EP250421a: Nickel optical upper limit
  36. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  37. EP250421a: Upper limits from Fermi-GBM Observations
  38. SVOM/sb25042207: XRT observations
  39. SVOM/sb25042207: BOOTES-2 early optical upper limit
  40. SVOM/sb25042207: GOTO optical upper limits
  41. GRB 250421A: AstroSat CZTI detection
  42. SVOM/sb25042207: SVOM detection of an X-ray transient
  43. GRB250419A: VLA radio detection
  44. IceCube-250421A: DDOTI Detection of the LAST Candidate
  45. GRB 250419A: Mephisto Multi-band Optical Detection
  46. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  47. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  48. EP250421a: NOT optical observations
  49. GRB 250419A: Optical Observations via Virtual Telescope Project
  50. EP250421a: REM optical upper limit
  51. EP250421a: Swift/XRT counterpart detection
  52. EP250421A: COLIBRÍ Optical Upper Limit
  53. GRB 250419A: Mondy Continued Optical Observations
  54. Fermi GRB 250421A: Global MASTER-Net observations report
  55. EP250421a: Global MASTER-Net observations report
  56. GRB 250421B: AstroSat CZTI detection of a bright long burst
  57. EP250421a: Einstein Probe detection of an X-ray transient
  58. EP250421a: Mephisto optical counterpart confirmation
  59. IceCube Alert 250421.71: Global MASTER-Net observations report
  60. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  61. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  62. EP250421a: JinShan likely optical counterpart
  63. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  64. GRB 250421A: Fermi GBM Final Real-time Localization
  65. GRB 250419A: Liverpool Telescope observations
  66. GRB 250419A: LCO optical observation
  67. GRB 250419A: JinShan optical observations
  68. GRB 250419A: SVOM/VT optical continuous observations
  69. GRB 250419A: SVOM/C-GFT optical observations
  70. GRB 250419A: Swift/UVOT Follow up
  71. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  72. GRB 250419A: LCO optical afterglow multi-band observations
  73. GRB 250419A: Mondy and AbAO Optical Observations
  74. GRB 250419A: Liverpool Telescope observations
  75. GRB 250419A: AKO Optical Afterglow Detection
  76. GRB 250419A: MASTER optical afterglow observation
  77. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  78. GRB 250407A: rest-frame energetics from Konus-Wind observation
  79. GRB 250419A: Swift-XRT localisation
  80. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  81. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  82. GRB 250419A: Swift-XRT refined Analysis
  83. GRB 250419A: GOTO optical counterpart detection
  84. GRB 250419A: KAIT optical afterglow observations
  85. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  86. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  87. GRB 250419A: SVOM detection of a soft burst
  88. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  89. EP250416a: Swift/XRT counterpart fading
  90. EP250416a: refined EP-WXT and EP-FXT analysis
  91. Konus-Wind detection of GRB 250403A
  92. EP20250416a: Swift/XRT counterpart detection
  93. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  94. IceCube-250416A: DDOTI Optical Observations
  95. EP250416a: Gemini South-GMOS optical counterpart
  96. EP250225a: SVOM/VT optical brightening
  97. SVOM/sb25041603 is not a GRB
  98. EP250416a: GSP optical upper limit
  99. EP250416a: Global MASTER-Net observations report
  100. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB

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