Skip to main content
Updates to LVK & CHIME Notices, Schema v7.2.3! See news and announcements

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"

20951 results found.

  1. GRB 250419A: Mondy Continued Optical Observations
  2. Fermi GRB 250421A: Global MASTER-Net observations report
  3. EP250421a: Global MASTER-Net observations report
  4. EP250421a: Mephisto optical counterpart confirmation
  5. IceCube Alert 250421.71: Global MASTER-Net observations report
  6. EP250421a: JinShan likely optical counterpart
  7. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  8. GRB 250419A: Liverpool Telescope observations
  9. GRB 250419A: LCO optical observation
  10. GRB 250419A: JinShan optical observations
  11. GRB 250419A: SVOM/VT optical continuous observations
  12. GRB 250419A: SVOM/C-GFT optical observations
  13. GRB 250419A: Swift/UVOT Follow up
  14. GRB 250419A: LCO optical afterglow multi-band observations
  15. GRB 250419A: Mondy and AbAO Optical Observations
  16. GRB 250419A: Liverpool Telescope observations
  17. GRB 250419A: AKO Optical Afterglow Detection
  18. GRB 250419A: MASTER optical afterglow observation
  19. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  20. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  21. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  22. GRB 250419A: GOTO optical counterpart detection
  23. GRB 250419A: KAIT optical afterglow observations
  24. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  25. EP250416a: Swift/XRT counterpart fading
  26. EP250416a: refined EP-WXT and EP-FXT analysis
  27. EP20250416a: Swift/XRT counterpart detection
  28. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  29. IceCube-250416A: DDOTI Optical Observations
  30. EP250416a: Gemini South-GMOS optical counterpart
  31. EP250225a: SVOM/VT optical brightening
  32. EP250416a: GSP optical upper limit
  33. EP250416a: Global MASTER-Net observations report
  34. IceCube-250416A: Global MASTER-Net observations report
  35. IceCube 250414.324: DDOTI Optical Observations
  36. EP250304a: ATCA radio observations
  37. EP250404a: Nanshan 0.43m Telescope optical observatios
  38. Fermi trigger No 766148493: Global MASTER-Net observations report
  39. Fermi trigger No 766173972: Global MASTER-Net observations report
  40. GRB 250411A: DDOTI Optical Observations
  41. Fermi GRB 250411A: Global MASTER-Net observations report
  42. GRB 250407A: Continued KAIT/Nickel optical observations
  43. GRB 250314A: e-MERLIN observations
  44. GRB 250407A: Mondy and AbAO Optical Observations
  45. EP250227a: Further NOT optical observations
  46. IceCube-250406A: Swift-XRT observations
  47. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  48. EP250407a: Global MASTER-Net observations report
  49. GRB 250407A: LCO detection of a fading optical counterpart
  50. Fermi-LAT gamma-ray observations of IceCube-250406A
  51. EP250407a: Swift-XRT observations
  52. EP250407a: EP-WXT detection of a fast X-ray transient
  53. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  54. GRB 250407A: KAIT Optical Afterglow Candidate
  55. IceCube-250406A: No candidates from the Zwicky Transient Facility
  56. GRB 250407A: Swift-XRT afterglow detection
  57. Fermi GRB 250407A: Global MASTER-Net observations report
  58. GRB 250407A: Swift ToO observations
  59. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  60. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  61. IceCube 250406.951: DDOTI Optical Observations
  62. IceCube Alert 250406.95: Global MASTER-Net observations report
  63. Fermi trigger No 765663719: Global MASTER-Net observations report
  64. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  65. Fermi GRB 250406A: Global MASTER-Net observations report
  66. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  67. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  68. Fermi trigger No 765619921: Global MASTER-Net observations report
  69. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  70. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  71. GRB 250404A / EP250404a: Mondy optical observations
  72. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  73. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  74. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  75. EP250402a: Optical upper limit with PD 1.3m observations
  76. GRB 250404A / EP250404a: NOT optical observations
  77. GRB 250331D: Swift-XRT afterglow detection
  78. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  79. EP250404a: REM optical/NIR observations
  80. EP250404a: Seimei/TriCCS optical counterpart detection
  81. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  82. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  83. EP250404a: LCO optical counterpart detection
  84. Fermi GRB 250404A: Global MASTER-Net observations report
  85. EP250404a: Xinglong decaying optical counterpart
  86. GRB 250403A: Montarrenti Observatory optical detection
  87. EP250404a: Global MASTER-Net observations report
  88. GRB 250403A: KAIT optical observations
  89. EP250404a: AKO Optical Afterglow Detection
  90. EP250404a: LAST detection of optical counterpart
  91. GRB 250403A: Fermi GBM observations
  92. EP250404a: Mephisto multi-band optical detection
  93. EP250321A: J band upper limit by SYSU 80cm telescope
  94. EP250404a: Nanshan/HMT optical counterpart detection
  95. GRB 250402A: Mondy optical observations
  96. EP250402a: Optical upper limit with Kinder observations
  97. GRB 250403A: REM NIR afterglow detection
  98. GRB 250403A: LCO optical counterpart detection
  99. GRB 250403A: JinShan optical observations
  100. GRB 250403A: Optical counterpart detection by LCO.

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
Looking for U.S. government information and services? Visit USA.gov