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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"

35953 results found.

  1. GRB 250419A: Mondy Optical Observations
  2. GRB 250424A: Swift/UVOT Detection
  3. Konus-Wind detection of GRB 250424A
  4. GRB 250424A: Skynet Optical Observations
  5. GRB 250424A: Kilonova-Catcher optical afterglow detection
  6. GRB 250419a: Continued Liverpool Telescope observations
  7. GRB 250419A: Liverpool Telescope optical upper limit
  8. GRB 250407A: GRBAlpha detection
  9. GRB 250404A / EP250404a: GRBAlpha detection
  10. GRB 250330B: GRBAlpha detection
  11. GRB 250419A: SVOM/ECLAIRs refined analysis
  12. GRB 250424A: Swift-XRT refined Analysis
  13. GRB 250424A: Enhanced Swift-XRT position
  14. GRB 250424A: AstroSat CZTI detection of a bright long burst
  15. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  16. GRB 250424A: BlackGEM optical afterglow detection
  17. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  18. GRB 250424A: likely host galaxy
  19. GRB 250424A: DDOTI Afterglow Detection
  20. GRB 250424A: REM optical/NIR afterglow detection
  21. GRB 250424A: Swift detection of a burst with an optical counterpart
  22. Swift GRB 250424A: Global MASTER-Net observations report
  23. Swift GRB 250424A: Global MASTER-Net OT detection
  24. EP250421a: Nickel optical upper limit
  25. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  26. EP250421a: Upper limits from Fermi-GBM Observations
  27. SVOM/sb25042207: GOTO optical upper limits
  28. GRB 250421A: AstroSat CZTI detection
  29. GRB250419A: VLA radio detection
  30. GRB 250419A: Mephisto Multi-band Optical Detection
  31. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  32. GRB 250419A: Optical Observations via Virtual Telescope Project
  33. GRB 250419A: Mondy Continued Optical Observations
  34. Fermi GRB 250421A: Global MASTER-Net observations report
  35. GRB 250421B: AstroSat CZTI detection of a bright long burst
  36. GRB 250421A: Fermi GBM Final Real-time Localization
  37. GRB 250419A: Liverpool Telescope observations
  38. GRB 250419A: LCO optical observation
  39. GRB 250419A: JinShan optical observations
  40. GRB 250419A: SVOM/VT optical continuous observations
  41. GRB 250419A: SVOM/C-GFT optical observations
  42. GRB 250419A: Swift/UVOT Follow up
  43. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  44. GRB 250419A: LCO optical afterglow multi-band observations
  45. GRB 250419A: Mondy and AbAO Optical Observations
  46. GRB 250419A: Liverpool Telescope observations
  47. GRB 250419A: AKO Optical Afterglow Detection
  48. GRB 250419A: MASTER optical afterglow observation
  49. GRB 250407A: rest-frame energetics from Konus-Wind observation
  50. GRB 250419A: Swift-XRT localisation
  51. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  52. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  53. GRB 250419A: Swift-XRT refined Analysis
  54. GRB 250419A: GOTO optical counterpart detection
  55. GRB 250419A: KAIT optical afterglow observations
  56. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  57. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  58. GRB 250419A: SVOM detection of a soft burst
  59. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  60. Konus-Wind detection of GRB 250403A
  61. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  62. SVOM/sb25041603 is not a GRB
  63. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  64. Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
  65. GRB 250416B: Fermi GBM Final Real-time Localization
  66. GRB 250416A: Fermi GBM Final Real-time Localization
  67. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  68. GRB 250413A: AstroSat CZTI detection
  69. EP250304a: ATCA radio observations
  70. GRB 250412A: AstroSat CZTI detection
  71. GRB 250411A: DDOTI Optical Observations
  72. Fermi GRB 250411A: Global MASTER-Net observations report
  73. GRB 250411A: Fermi GBM Final Real-time Localization
  74. GRB 250407A: Continued KAIT/Nickel optical observations
  75. GRB 250314A: e-MERLIN observations
  76. GRB 250407A: Mondy and AbAO Optical Observations
  77. GRB 250320B: cubesat Avion detection
  78. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  79. IPN triangulation of GRB 250407A
  80. GRB 250407A: LCO detection of a fading optical counterpart
  81. EP250407a: Swift-XRT observations
  82. Konus-Wind detection of GRB 250407A
  83. GRB 250407A: SVOM/GRM observation of a bright long burst
  84. GRB 250407A: EP-WXT afterglow detection
  85. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  86. GRB 250407A: KAIT Optical Afterglow Candidate
  87. GRB 250407A: Fermi GBM Detection
  88. GRB 250407A: Swift-XRT afterglow detection
  89. Fermi GRB 250407A: Global MASTER-Net observations report
  90. GRB 250407A: Swift ToO observations
  91. GRB 250407A: SRG/ART-XC afterglow detection
  92. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  93. Konus-Wind detection of GRB 250406B (short/hard)
  94. IPN triangulation of GRB 250406B (short/hard)
  95. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  96. GRB 250407A: Fermi GBM Final Real-time Localization
  97. GRB 250406A: AstroSat CZTI detection
  98. Fermi GRB 250406A: Global MASTER-Net observations report
  99. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  100. GRB 250406A: Fermi GBM Final Real-time Localization

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