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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"

32509 results found.

  1. GRB 250427A: Swift-XRT refined Analysis
  2. EP250427a / GRB 250427A: LCO optical counterpart detection
  3. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  4. EP250427A/GRB250427A: Keck/LRIS redshift
  5. EP250427a: REM optical/NIR afterglow detection
  6. GRB 250424A: LCO optical observation
  7. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  8. EP250427A: COLIBRÍ Optical Detection
  9. EP250427a: TRT optical counterpart detection
  10. EP250427a: Global MASTER-Net observations report
  11. EP250427a: Einstein Probe detection of a fast X-ray transient
  12. GRB 250424A: Swift-BAT refined analysis
  13. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  14. GRB 250424A: SVOM/GRM observation of a long burst
  15. GRB 250424A: PRIME near-infrared detection
  16. GRB 250424A: WINTER J-band detection
  17. GRB 250424A: EIRSAT-1 GMOD Detection
  18. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  19. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  20. GRB 250424A: SVOM/VT optical observation
  21. GRB 250419A: Mondy Optical Observations
  22. GRB 250424A: Swift/UVOT Detection
  23. Konus-Wind detection of GRB 250424A
  24. Fermi-LAT gamma-ray observations of IceCube-250421A
  25. GRB 250424A: Skynet Optical Observations
  26. GRB 250424A: Kilonova-Catcher optical afterglow detection
  27. GRB 250419a: Continued Liverpool Telescope observations
  28. GRB 250419A: Liverpool Telescope optical upper limit
  29. GRB 250407A: GRBAlpha detection
  30. GRB 250404A / EP250404a: GRBAlpha detection
  31. GRB 250330B: GRBAlpha detection
  32. GRB 250419A: SVOM/ECLAIRs refined analysis
  33. GRB 250424A: AstroSat CZTI detection of a bright long burst
  34. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  35. GRB 250424A: BlackGEM optical afterglow detection
  36. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  37. GRB 250424A: likely host galaxy
  38. GRB 250424A: DDOTI Afterglow Detection
  39. GRB 250424A: REM optical/NIR afterglow detection
  40. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  41. EP250421a: Nickel optical upper limit
  42. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  43. EP250421a: Upper limits from Fermi-GBM Observations
  44. SVOM/sb25042207: XRT observations
  45. SVOM/sb25042207: BOOTES-2 early optical upper limit
  46. SVOM/sb25042207: GOTO optical upper limits
  47. GRB 250421A: AstroSat CZTI detection
  48. GRB250419A: VLA radio detection
  49. IceCube-250421A: DDOTI Detection of the LAST Candidate
  50. GRB 250419A: Mephisto Multi-band Optical Detection
  51. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  52. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  53. EP250421a: NOT optical observations
  54. GRB 250419A: Optical Observations via Virtual Telescope Project
  55. EP250421a: REM optical upper limit
  56. EP250421a: Swift/XRT counterpart detection
  57. EP250421A: COLIBRÍ Optical Upper Limit
  58. GRB 250419A: Mondy Continued Optical Observations
  59. Fermi GRB 250421A: Global MASTER-Net observations report
  60. EP250421a: Global MASTER-Net observations report
  61. EP250421a: Mephisto optical counterpart confirmation
  62. GRB 250419A: Liverpool Telescope observations
  63. GRB 250419A: LCO optical observation
  64. GRB 250419A: JinShan optical observations
  65. GRB 250419A: SVOM/VT optical continuous observations
  66. GRB 250419A: SVOM/C-GFT optical observations
  67. GRB 250419A: Swift/UVOT Follow up
  68. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  69. GRB 250419A: LCO optical afterglow multi-band observations
  70. GRB 250419A: Mondy and AbAO Optical Observations
  71. GRB 250419A: Liverpool Telescope observations
  72. GRB 250419A: AKO Optical Afterglow Detection
  73. GRB 250419A: MASTER optical afterglow observation
  74. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  75. GRB 250407A: rest-frame energetics from Konus-Wind observation
  76. GRB 250419A: Swift-XRT localisation
  77. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  78. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  79. GRB 250419A: Swift-XRT refined Analysis
  80. GRB 250419A: GOTO optical counterpart detection
  81. GRB 250419A: KAIT optical afterglow observations
  82. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  83. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  84. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  85. EP250416a: Swift/XRT counterpart fading
  86. EP250416a: refined EP-WXT and EP-FXT analysis
  87. Konus-Wind detection of GRB 250403A
  88. EP20250416a: Swift/XRT counterpart detection
  89. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  90. IceCube-250416A: DDOTI Optical Observations
  91. EP250416a: Gemini South-GMOS optical counterpart
  92. EP250225a: SVOM/VT optical brightening
  93. SVOM/sb25041603 is not a GRB
  94. EP250416a: GSP optical upper limit
  95. EP250416a: Global MASTER-Net observations report
  96. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  97. GRB 250413A: AstroSat CZTI detection
  98. EP250304a: ATCA radio observations
  99. EP250404a: Nanshan 0.43m Telescope optical observatios
  100. GRB 250411A: DDOTI Optical Observations

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