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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"
  1. GRB 250419A: JinShan optical observations
  2. GRB 250419A: SVOM/VT optical continuous observations
  3. GRB 250419A: SVOM/C-GFT optical observations
  4. GRB 250419A: Swift/UVOT Follow up
  5. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  6. GRB 250419A: LCO optical afterglow multi-band observations
  7. GRB 250419A: Mondy and AbAO Optical Observations
  8. GRB 250419A: Liverpool Telescope observations
  9. GRB 250419A: AKO Optical Afterglow Detection
  10. GRB 250419A: MASTER optical afterglow observation
  11. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  12. GRB 250407A: rest-frame energetics from Konus-Wind observation
  13. GRB 250419A: Swift-XRT localisation
  14. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  15. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  16. GRB 250419A: Swift-XRT refined Analysis
  17. GRB 250419A: GOTO optical counterpart detection
  18. GRB 250419A: KAIT optical afterglow observations
  19. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  20. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  21. GRB 250419A: SVOM detection of a soft burst
  22. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  23. EP250416a: Swift/XRT counterpart fading
  24. EP250416a: refined EP-WXT and EP-FXT analysis
  25. Konus-Wind detection of GRB 250403A
  26. EP20250416a: Swift/XRT counterpart detection
  27. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  28. IceCube-250416A: DDOTI Optical Observations
  29. EP250416a: Gemini South-GMOS optical counterpart
  30. EP250225a: SVOM/VT optical brightening
  31. SVOM/sb25041603 is not a GRB
  32. EP250416a: GSP optical upper limit
  33. EP250416a: Global MASTER-Net observations report
  34. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  35. EP250416a: Einstein Probe detection of an X-ray transient
  36. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  37. IceCube-250416A: Global MASTER-Net observations report
  38. Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
  39. GRB 250416B: Fermi GBM Final Real-time Localization
  40. GRB 250416A: Fermi GBM Final Real-time Localization
  41. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  42. SVOM/sb25041603: SVOM detection of an X-ray transient
  43. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  44. IceCube 250414.324: DDOTI Optical Observations
  45. GRB 250413A: AstroSat CZTI detection
  46. EP250304a: ATCA radio observations
  47. GRB 250412A: AstroSat CZTI detection
  48. EP250404a: Nanshan 0.43m Telescope optical observatios
  49. Fermi trigger No 766148493: Global MASTER-Net observations report
  50. Fermi trigger No 766173972: Global MASTER-Net observations report
  51. GRB 250411A: DDOTI Optical Observations
  52. Fermi GRB 250411A: Global MASTER-Net observations report
  53. GRB 250411A: Fermi GBM Final Real-time Localization
  54. GRB 250407A: Continued KAIT/Nickel optical observations
  55. GRB 250314A: e-MERLIN observations
  56. GRB 250407A: Mondy and AbAO Optical Observations
  57. EP250227a: Further NOT optical observations
  58. GRB 250320B: cubesat Avion detection
  59. IceCube-250406A: Swift-XRT observations
  60. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  61. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  62. IPN triangulation of GRB 250407A
  63. EP250407a: Global MASTER-Net observations report
  64. GRB 250407A: LCO detection of a fading optical counterpart
  65. Fermi-LAT gamma-ray observations of IceCube-250406A
  66. EP250407a: Swift-XRT observations
  67. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  68. Konus-Wind detection of GRB 250407A
  69. GRB 250407A: SVOM/GRM observation of a bright long burst
  70. GRB 250407A: EP-WXT afterglow detection
  71. EP250407a: EP-WXT detection of a fast X-ray transient
  72. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  73. GRB 250407A: KAIT Optical Afterglow Candidate
  74. IceCube-250406A: No candidates from the Zwicky Transient Facility
  75. GRB 250407A: Fermi GBM Detection
  76. GRB 250407A: Swift-XRT afterglow detection
  77. Fermi GRB 250407A: Global MASTER-Net observations report
  78. GRB 250407A: Swift ToO observations
  79. GRB 250407A: SRG/ART-XC afterglow detection
  80. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  81. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  82. Konus-Wind detection of GRB 250406B (short/hard)
  83. IPN triangulation of GRB 250406B (short/hard)
  84. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  85. GRB 250407A: Fermi GBM Final Real-time Localization
  86. IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event
  87. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  88. IceCube 250406.951: DDOTI Optical Observations
  89. GRB 250406A: AstroSat CZTI detection
  90. IceCube Alert 250406.95: Global MASTER-Net observations report
  91. Fermi trigger No 765663719: Global MASTER-Net observations report
  92. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  93. Fermi GRB 250406A: Global MASTER-Net observations report
  94. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  95. GRB 250406A: Fermi GBM Final Real-time Localization
  96. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  97. Fermi trigger No 765619921: Global MASTER-Net observations report
  98. Fermi Gamma-ray Burst Monitor trigger 765619921/250406342 is not a GRB
  99. GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit
  100. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations

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