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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"

32506 results found.

  1. EP250427A/GRB250427A: Keck/LRIS redshift
  2. EP250427a: REM optical/NIR afterglow detection
  3. GRB 250424A: LCO optical observation
  4. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  5. EP250427A: COLIBRÍ Optical Detection
  6. EP250427a: TRT optical counterpart detection
  7. EP250427a: Global MASTER-Net observations report
  8. EP250427a: Einstein Probe detection of a fast X-ray transient
  9. GRB 250424A: Swift-BAT refined analysis
  10. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  11. GRB 250424A: SVOM/GRM observation of a long burst
  12. GRB 250424A: PRIME near-infrared detection
  13. GRB 250424A: WINTER J-band detection
  14. GRB 250424A: EIRSAT-1 GMOD Detection
  15. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  16. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  17. GRB 250424A: SVOM/VT optical observation
  18. GRB 250419A: Mondy Optical Observations
  19. GRB 250424A: Swift/UVOT Detection
  20. Konus-Wind detection of GRB 250424A
  21. Fermi-LAT gamma-ray observations of IceCube-250421A
  22. GRB 250424A: Skynet Optical Observations
  23. GRB 250424A: Kilonova-Catcher optical afterglow detection
  24. GRB 250419a: Continued Liverpool Telescope observations
  25. GRB 250419A: Liverpool Telescope optical upper limit
  26. GRB 250407A: GRBAlpha detection
  27. GRB 250404A / EP250404a: GRBAlpha detection
  28. GRB 250330B: GRBAlpha detection
  29. GRB 250419A: SVOM/ECLAIRs refined analysis
  30. GRB 250424A: AstroSat CZTI detection of a bright long burst
  31. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  32. GRB 250424A: BlackGEM optical afterglow detection
  33. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  34. GRB 250424A: likely host galaxy
  35. GRB 250424A: DDOTI Afterglow Detection
  36. GRB 250424A: REM optical/NIR afterglow detection
  37. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  38. EP250421a: Nickel optical upper limit
  39. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  40. EP250421a: Upper limits from Fermi-GBM Observations
  41. SVOM/sb25042207: XRT observations
  42. SVOM/sb25042207: BOOTES-2 early optical upper limit
  43. SVOM/sb25042207: GOTO optical upper limits
  44. GRB 250421A: AstroSat CZTI detection
  45. GRB250419A: VLA radio detection
  46. IceCube-250421A: DDOTI Detection of the LAST Candidate
  47. GRB 250419A: Mephisto Multi-band Optical Detection
  48. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  49. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  50. EP250421a: NOT optical observations
  51. GRB 250419A: Optical Observations via Virtual Telescope Project
  52. EP250421a: REM optical upper limit
  53. EP250421a: Swift/XRT counterpart detection
  54. EP250421A: COLIBRÍ Optical Upper Limit
  55. GRB 250419A: Mondy Continued Optical Observations
  56. Fermi GRB 250421A: Global MASTER-Net observations report
  57. EP250421a: Global MASTER-Net observations report
  58. EP250421a: Mephisto optical counterpart confirmation
  59. GRB 250419A: Liverpool Telescope observations
  60. GRB 250419A: LCO optical observation
  61. GRB 250419A: JinShan optical observations
  62. GRB 250419A: SVOM/VT optical continuous observations
  63. GRB 250419A: SVOM/C-GFT optical observations
  64. GRB 250419A: Swift/UVOT Follow up
  65. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  66. GRB 250419A: LCO optical afterglow multi-band observations
  67. GRB 250419A: Mondy and AbAO Optical Observations
  68. GRB 250419A: Liverpool Telescope observations
  69. GRB 250419A: AKO Optical Afterglow Detection
  70. GRB 250419A: MASTER optical afterglow observation
  71. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  72. GRB 250407A: rest-frame energetics from Konus-Wind observation
  73. GRB 250419A: Swift-XRT localisation
  74. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  75. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  76. GRB 250419A: Swift-XRT refined Analysis
  77. GRB 250419A: GOTO optical counterpart detection
  78. GRB 250419A: KAIT optical afterglow observations
  79. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  80. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  81. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  82. EP250416a: Swift/XRT counterpart fading
  83. EP250416a: refined EP-WXT and EP-FXT analysis
  84. Konus-Wind detection of GRB 250403A
  85. EP20250416a: Swift/XRT counterpart detection
  86. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  87. IceCube-250416A: DDOTI Optical Observations
  88. EP250416a: Gemini South-GMOS optical counterpart
  89. EP250225a: SVOM/VT optical brightening
  90. SVOM/sb25041603 is not a GRB
  91. EP250416a: GSP optical upper limit
  92. EP250416a: Global MASTER-Net observations report
  93. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  94. GRB 250413A: AstroSat CZTI detection
  95. EP250304a: ATCA radio observations
  96. EP250404a: Nanshan 0.43m Telescope optical observatios
  97. GRB 250411A: DDOTI Optical Observations
  98. Fermi GRB 250411A: Global MASTER-Net observations report
  99. GRB 250407A: Continued KAIT/Nickel optical observations
  100. GRB 250314A: e-MERLIN observations

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