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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"

32513 results found.

  1. EP250427a: Lesedi optical counterpart detection
  2. EP250427A: COLIBRÍ Continuing Optical Observations
  3. GRB250427A/EP250427a GIT optical afterglow detection:
  4. EP250427a: LT optical counterpart detection
  5. GRB 250427A: Swift-XRT refined Analysis
  6. EP250427a / GRB 250427A: LCO optical counterpart detection
  7. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  8. EP250427A/GRB250427A: Keck/LRIS redshift
  9. EP250427a: REM optical/NIR afterglow detection
  10. GRB 250424A: LCO optical observation
  11. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  12. EP250427A: COLIBRÍ Optical Detection
  13. EP250427a: TRT optical counterpart detection
  14. EP250427a: Global MASTER-Net observations report
  15. EP250427a: Einstein Probe detection of a fast X-ray transient
  16. GRB 250424A: Swift-BAT refined analysis
  17. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  18. GRB 250424A: SVOM/GRM observation of a long burst
  19. GRB 250424A: PRIME near-infrared detection
  20. GRB 250424A: WINTER J-band detection
  21. GRB 250424A: EIRSAT-1 GMOD Detection
  22. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  23. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  24. GRB 250424A: SVOM/VT optical observation
  25. GRB 250419A: Mondy Optical Observations
  26. GRB 250424A: Swift/UVOT Detection
  27. Konus-Wind detection of GRB 250424A
  28. Fermi-LAT gamma-ray observations of IceCube-250421A
  29. GRB 250424A: Skynet Optical Observations
  30. GRB 250424A: Kilonova-Catcher optical afterglow detection
  31. GRB 250419a: Continued Liverpool Telescope observations
  32. GRB 250419A: Liverpool Telescope optical upper limit
  33. GRB 250407A: GRBAlpha detection
  34. GRB 250404A / EP250404a: GRBAlpha detection
  35. GRB 250330B: GRBAlpha detection
  36. GRB 250419A: SVOM/ECLAIRs refined analysis
  37. GRB 250424A: AstroSat CZTI detection of a bright long burst
  38. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  39. GRB 250424A: BlackGEM optical afterglow detection
  40. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  41. GRB 250424A: likely host galaxy
  42. GRB 250424A: DDOTI Afterglow Detection
  43. GRB 250424A: REM optical/NIR afterglow detection
  44. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  45. EP250421a: Nickel optical upper limit
  46. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  47. EP250421a: Upper limits from Fermi-GBM Observations
  48. SVOM/sb25042207: XRT observations
  49. SVOM/sb25042207: BOOTES-2 early optical upper limit
  50. SVOM/sb25042207: GOTO optical upper limits
  51. GRB 250421A: AstroSat CZTI detection
  52. GRB250419A: VLA radio detection
  53. IceCube-250421A: DDOTI Detection of the LAST Candidate
  54. GRB 250419A: Mephisto Multi-band Optical Detection
  55. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  56. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  57. EP250421a: NOT optical observations
  58. GRB 250419A: Optical Observations via Virtual Telescope Project
  59. EP250421a: REM optical upper limit
  60. EP250421a: Swift/XRT counterpart detection
  61. EP250421A: COLIBRÍ Optical Upper Limit
  62. GRB 250419A: Mondy Continued Optical Observations
  63. Fermi GRB 250421A: Global MASTER-Net observations report
  64. EP250421a: Global MASTER-Net observations report
  65. EP250421a: Mephisto optical counterpart confirmation
  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. 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. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart

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