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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"

32531 results found.

  1. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  2. GRB 250430A: AKO Optical Afterglow Detection
  3. GRB 250430A: Kanata optical upper limit
  4. EP 250427A: Optical counterpart detection by LCO.
  5. EP250428b: FTW optical and NIR observations
  6. EP250427a/GRB250427A: HCT optical follow-up
  7. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  8. EP250428b: refined analysis of the EP-FXT follow-up observation
  9. EP250428b: GROWTH-India telescope optical upper limit
  10. EP250428b: SVOM/VT upper limit
  11. EP250428b: SAO RAS optical upper limit
  12. EP250428b: LAST optical upper limit
  13. GRB 250427A: Swift/UVOT Detection
  14. EP250428b: Global MASTER-Net observations report
  15. EP250428b: Einstein Probe detection of a fast X-ray transient
  16. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  17. EP250427a / GRB 250427A: OHP/T193 photometric observations
  18. EP250427a: EP-FXT follow-up observations
  19. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  20. EP250427a: Lesedi optical counterpart detection
  21. EP250427A: COLIBRÍ Continuing Optical Observations
  22. GRB250427A/EP250427a GIT optical afterglow detection:
  23. EP250427a: LT optical counterpart detection
  24. GRB 250427A: Swift-XRT refined Analysis
  25. EP250427a / GRB 250427A: LCO optical counterpart detection
  26. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  27. EP250427A/GRB250427A: Keck/LRIS redshift
  28. EP250427a: REM optical/NIR afterglow detection
  29. GRB 250424A: LCO optical observation
  30. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  31. EP250427A: COLIBRÍ Optical Detection
  32. EP250427a: TRT optical counterpart detection
  33. EP250427a: Global MASTER-Net observations report
  34. EP250427a: Einstein Probe detection of a fast X-ray transient
  35. GRB 250424A: Swift-BAT refined analysis
  36. IceCube-250426A - IceCube observation of a high-energy neutrino candidate track-like event (duplicate submission)
  37. GRB 250424A: SVOM/GRM observation of a long burst
  38. GRB 250424A: PRIME near-infrared detection
  39. GRB 250424A: WINTER J-band detection
  40. GRB 250424A: EIRSAT-1 GMOD Detection
  41. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  42. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  43. GRB 250424A: SVOM/VT optical observation
  44. GRB 250419A: Mondy Optical Observations
  45. GRB 250424A: Swift/UVOT Detection
  46. Konus-Wind detection of GRB 250424A
  47. Fermi-LAT gamma-ray observations of IceCube-250421A
  48. GRB 250424A: Skynet Optical Observations
  49. GRB 250424A: Kilonova-Catcher optical afterglow detection
  50. GRB 250419a: Continued Liverpool Telescope observations
  51. GRB 250419A: Liverpool Telescope optical upper limit
  52. GRB 250407A: GRBAlpha detection
  53. GRB 250404A / EP250404a: GRBAlpha detection
  54. GRB 250330B: GRBAlpha detection
  55. GRB 250419A: SVOM/ECLAIRs refined analysis
  56. GRB 250424A: AstroSat CZTI detection of a bright long burst
  57. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  58. GRB 250424A: BlackGEM optical afterglow detection
  59. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  60. GRB 250424A: likely host galaxy
  61. GRB 250424A: DDOTI Afterglow Detection
  62. GRB 250424A: REM optical/NIR afterglow detection
  63. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  64. EP250421a: Nickel optical upper limit
  65. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  66. EP250421a: Upper limits from Fermi-GBM Observations
  67. SVOM/sb25042207: XRT observations
  68. SVOM/sb25042207: BOOTES-2 early optical upper limit
  69. SVOM/sb25042207: GOTO optical upper limits
  70. GRB 250421A: AstroSat CZTI detection
  71. GRB250419A: VLA radio detection
  72. IceCube-250421A: DDOTI Detection of the LAST Candidate
  73. GRB 250419A: Mephisto Multi-band Optical Detection
  74. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  75. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  76. EP250421a: NOT optical observations
  77. GRB 250419A: Optical Observations via Virtual Telescope Project
  78. EP250421a: REM optical upper limit
  79. EP250421a: Swift/XRT counterpart detection
  80. EP250421A: COLIBRÍ Optical Upper Limit
  81. GRB 250419A: Mondy Continued Optical Observations
  82. Fermi GRB 250421A: Global MASTER-Net observations report
  83. EP250421a: Global MASTER-Net observations report
  84. EP250421a: Mephisto optical counterpart confirmation
  85. GRB 250419A: Liverpool Telescope observations
  86. GRB 250419A: LCO optical observation
  87. GRB 250419A: JinShan optical observations
  88. GRB 250419A: SVOM/VT optical continuous observations
  89. GRB 250419A: SVOM/C-GFT optical observations
  90. GRB 250419A: Swift/UVOT Follow up
  91. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  92. GRB 250419A: LCO optical afterglow multi-band observations
  93. GRB 250419A: Mondy and AbAO Optical Observations
  94. GRB 250419A: Liverpool Telescope observations
  95. GRB 250419A: AKO Optical Afterglow Detection
  96. GRB 250419A: MASTER optical afterglow observation
  97. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  98. GRB 250407A: rest-frame energetics from Konus-Wind observation
  99. GRB 250419A: Swift-XRT localisation
  100. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36

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