Skip to main content
Due to the lapse in federal government funding, NASA is not updating this website. See the Operations FAQ for GCN impacts.
New! Super-Kamiokande JSON Notices and Schema v4.5.0. 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"
  1. GRB 250419A: Mephisto Multi-band Optical Detection
  2. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  3. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  4. EP250421a: NOT optical observations
  5. GRB 250419A: Optical Observations via Virtual Telescope Project
  6. EP250421a: REM optical upper limit
  7. EP250421a: Swift/XRT counterpart detection
  8. EP250421A: COLIBRÍ Optical Upper Limit
  9. GRB 250419A: Mondy Continued Optical Observations
  10. Fermi GRB 250421A: Global MASTER-Net observations report
  11. EP250421a: Global MASTER-Net observations report
  12. GRB 250421B: AstroSat CZTI detection of a bright long burst
  13. EP250421a: Einstein Probe detection of an X-ray transient
  14. EP250421a: Mephisto optical counterpart confirmation
  15. IceCube Alert 250421.71: Global MASTER-Net observations report
  16. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  17. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  18. EP250421a: JinShan likely optical counterpart
  19. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  20. GRB 250421A: Fermi GBM Final Real-time Localization
  21. GRB 250419A: Liverpool Telescope observations
  22. GRB 250419A: LCO optical observation
  23. GRB 250419A: JinShan optical observations
  24. GRB 250419A: SVOM/VT optical continuous observations
  25. GRB 250419A: SVOM/C-GFT optical observations
  26. GRB 250419A: Swift/UVOT Follow up
  27. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  28. GRB 250419A: LCO optical afterglow multi-band observations
  29. GRB 250419A: Mondy and AbAO Optical Observations
  30. GRB 250419A: Liverpool Telescope observations
  31. GRB 250419A: AKO Optical Afterglow Detection
  32. GRB 250419A: MASTER optical afterglow observation
  33. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  34. GRB 250407A: rest-frame energetics from Konus-Wind observation
  35. GRB 250419A: Swift-XRT localisation
  36. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  37. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  38. GRB 250419A: Swift-XRT refined Analysis
  39. GRB 250419A: GOTO optical counterpart detection
  40. GRB 250419A: KAIT optical afterglow observations
  41. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  42. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  43. GRB 250419A: SVOM detection of a soft burst
  44. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  45. EP250416a: Swift/XRT counterpart fading
  46. EP250416a: refined EP-WXT and EP-FXT analysis
  47. Konus-Wind detection of GRB 250403A
  48. EP20250416a: Swift/XRT counterpart detection
  49. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  50. IceCube-250416A: DDOTI Optical Observations
  51. EP250416a: Gemini South-GMOS optical counterpart
  52. EP250225a: SVOM/VT optical brightening
  53. SVOM/sb25041603 is not a GRB
  54. EP250416a: GSP optical upper limit
  55. EP250416a: Global MASTER-Net observations report
  56. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  57. EP250416a: Einstein Probe detection of an X-ray transient
  58. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  59. IceCube-250416A: Global MASTER-Net observations report
  60. Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
  61. GRB 250416B: Fermi GBM Final Real-time Localization
  62. GRB 250416A: Fermi GBM Final Real-time Localization
  63. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  64. SVOM/sb25041603: SVOM detection of an X-ray transient
  65. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  66. IceCube 250414.324: DDOTI Optical Observations
  67. GRB 250413A: AstroSat CZTI detection
  68. EP250304a: ATCA radio observations
  69. GRB 250412A: AstroSat CZTI detection
  70. EP250404a: Nanshan 0.43m Telescope optical observatios
  71. Fermi trigger No 766148493: Global MASTER-Net observations report
  72. Fermi trigger No 766173972: Global MASTER-Net observations report
  73. GRB 250411A: DDOTI Optical Observations
  74. Fermi GRB 250411A: Global MASTER-Net observations report
  75. GRB 250411A: Fermi GBM Final Real-time Localization
  76. GRB 250407A: Continued KAIT/Nickel optical observations
  77. GRB 250314A: e-MERLIN observations
  78. GRB 250407A: Mondy and AbAO Optical Observations
  79. EP250227a: Further NOT optical observations
  80. GRB 250320B: cubesat Avion detection
  81. IceCube-250406A: Swift-XRT observations
  82. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  83. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  84. IPN triangulation of GRB 250407A
  85. EP250407a: Global MASTER-Net observations report
  86. GRB 250407A: LCO detection of a fading optical counterpart
  87. Fermi-LAT gamma-ray observations of IceCube-250406A
  88. EP250407a: Swift-XRT observations
  89. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  90. Konus-Wind detection of GRB 250407A
  91. GRB 250407A: SVOM/GRM observation of a bright long burst
  92. GRB 250407A: EP-WXT afterglow detection
  93. EP250407a: EP-WXT detection of a fast X-ray transient
  94. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  95. GRB 250407A: KAIT Optical Afterglow Candidate
  96. IceCube-250406A: No candidates from the Zwicky Transient Facility
  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

Advanced

Download all Circulars as a .tar.gz archive:
Questions or comments?
Contact GCN directly.
Have you found a bug in GCN?
Open an issue.
Want to contribute code to GCN?
Get involved on GitHub.

gcn.nasa.gov

A service of the Astrophysics Science Division at NASA Goddard Space Flight Center

Looking for U.S. government information and services? Visit USA.gov