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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"

35262 results found.

  1. EP250427a / GRB 250427A: VLT/X-shooter redshift confirmation z = 1.520
  2. EP250427A/GRB250427A: Keck/LRIS redshift
  3. GRB 250424A: LCO optical observation
  4. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  5. GRB 250424A: Swift-BAT refined analysis
  6. GRB 250424A: SVOM/GRM observation of a long burst
  7. GRB 250424A: PRIME near-infrared detection
  8. GRB 250424A: WINTER J-band detection
  9. GRB 250424A: EIRSAT-1 GMOD Detection
  10. GRB 250424A: SVOM/VT optical observation
  11. GRB 250419A: Mondy Optical Observations
  12. GRB 250424A: Swift/UVOT Detection
  13. Konus-Wind detection of GRB 250424A
  14. GRB 250424A: Skynet Optical Observations
  15. GRB 250424A: Kilonova-Catcher optical afterglow detection
  16. GRB 250419a: Continued Liverpool Telescope observations
  17. GRB 250419A: Liverpool Telescope optical upper limit
  18. GRB 250407A: GRBAlpha detection
  19. GRB 250404A / EP250404a: GRBAlpha detection
  20. GRB 250330B: GRBAlpha detection
  21. GRB 250419A: SVOM/ECLAIRs refined analysis
  22. GRB 250424A: Swift-XRT refined Analysis
  23. GRB 250424A: Enhanced Swift-XRT position
  24. GRB 250424A: AstroSat CZTI detection of a bright long burst
  25. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  26. GRB 250424A: BlackGEM optical afterglow detection
  27. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  28. GRB 250424A: likely host galaxy
  29. GRB 250424A: DDOTI Afterglow Detection
  30. GRB 250424A: REM optical/NIR afterglow detection
  31. GRB 250424A: Swift detection of a burst with an optical counterpart
  32. Swift GRB 250424A: Global MASTER-Net observations report
  33. Swift GRB 250424A: Global MASTER-Net OT detection
  34. EP250421a: Nickel optical upper limit
  35. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  36. EP250421a: Upper limits from Fermi-GBM Observations
  37. SVOM/sb25042207: GOTO optical upper limits
  38. GRB 250421A: AstroSat CZTI detection
  39. GRB250419A: VLA radio detection
  40. GRB 250419A: Mephisto Multi-band Optical Detection
  41. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  42. GRB 250419A: Optical Observations via Virtual Telescope Project
  43. GRB 250419A: Mondy Continued Optical Observations
  44. Fermi GRB 250421A: Global MASTER-Net observations report
  45. GRB 250421B: AstroSat CZTI detection of a bright long burst
  46. GRB 250421A: Fermi GBM Final Real-time Localization
  47. GRB 250419A: Liverpool Telescope observations
  48. GRB 250419A: LCO optical observation
  49. GRB 250419A: JinShan optical observations
  50. GRB 250419A: SVOM/VT optical continuous observations
  51. GRB 250419A: SVOM/C-GFT optical observations
  52. GRB 250419A: Swift/UVOT Follow up
  53. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  54. GRB 250419A: LCO optical afterglow multi-band observations
  55. GRB 250419A: Mondy and AbAO Optical Observations
  56. GRB 250419A: Liverpool Telescope observations
  57. GRB 250419A: AKO Optical Afterglow Detection
  58. GRB 250419A: MASTER optical afterglow observation
  59. GRB 250407A: rest-frame energetics from Konus-Wind observation
  60. GRB 250419A: Swift-XRT localisation
  61. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  62. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  63. GRB 250419A: Swift-XRT refined Analysis
  64. GRB 250419A: GOTO optical counterpart detection
  65. GRB 250419A: KAIT optical afterglow observations
  66. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  67. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  68. GRB 250419A: SVOM detection of a soft burst
  69. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  70. Konus-Wind detection of GRB 250403A
  71. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  72. SVOM/sb25041603 is not a GRB
  73. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  74. Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
  75. GRB 250416B: Fermi GBM Final Real-time Localization
  76. GRB 250416A: Fermi GBM Final Real-time Localization
  77. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  78. GRB 250413A: AstroSat CZTI detection
  79. EP250304a: ATCA radio observations
  80. GRB 250412A: AstroSat CZTI detection
  81. GRB 250411A: DDOTI Optical Observations
  82. Fermi GRB 250411A: Global MASTER-Net observations report
  83. GRB 250411A: Fermi GBM Final Real-time Localization
  84. GRB 250407A: Continued KAIT/Nickel optical observations
  85. GRB 250314A: e-MERLIN observations
  86. GRB 250407A: Mondy and AbAO Optical Observations
  87. GRB 250320B: cubesat Avion detection
  88. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  89. IPN triangulation of GRB 250407A
  90. GRB 250407A: LCO detection of a fading optical counterpart
  91. EP250407a: Swift-XRT observations
  92. Konus-Wind detection of GRB 250407A
  93. GRB 250407A: SVOM/GRM observation of a bright long burst
  94. GRB 250407A: EP-WXT afterglow detection
  95. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  96. GRB 250407A: KAIT Optical Afterglow Candidate
  97. GRB 250407A: Fermi GBM Detection
  98. GRB 250407A: Swift-XRT afterglow detection
  99. Fermi GRB 250407A: Global MASTER-Net observations report
  100. GRB 250407A: Swift ToO observations

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