Skip to main content
End of Swift Science Operations, CHIME Notices Unavailable During Upgrade. See news and announcements

GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

43933 results found.

  1. GRB 250424A: Swift detection of a burst with an optical counterpart
  2. Swift GRB 250424A: Global MASTER-Net observations report
  3. Swift GRB 250424A: Global MASTER-Net OT detection
  4. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  5. EP250421a: Nickel optical upper limit
  6. EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
  7. EP250421a: Upper limits from Fermi-GBM Observations
  8. SVOM/sb25042207: XRT observations
  9. SVOM/sb25042207: BOOTES-2 early optical upper limit
  10. SVOM/sb25042207: GOTO optical upper limits
  11. GRB 250421A: AstroSat CZTI detection
  12. SVOM/sb25042207: SVOM detection of an X-ray transient
  13. GRB250419A: VLA radio detection
  14. IceCube-250421A: DDOTI Detection of the LAST Candidate
  15. GRB 250419A: Mephisto Multi-band Optical Detection
  16. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  17. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  18. EP250421a: NOT optical observations
  19. GRB 250419A: Optical Observations via Virtual Telescope Project
  20. EP250421a: REM optical upper limit
  21. EP250421a: Swift/XRT counterpart detection
  22. EP250421A: COLIBRÍ Optical Upper Limit
  23. GRB 250419A: Mondy Continued Optical Observations
  24. Fermi GRB 250421A: Global MASTER-Net observations report
  25. EP250421a: Global MASTER-Net observations report
  26. GRB 250421B: AstroSat CZTI detection of a bright long burst
  27. EP250421a: Einstein Probe detection of an X-ray transient
  28. EP250421a: Mephisto optical counterpart confirmation
  29. IceCube Alert 250421.71: Global MASTER-Net observations report
  30. IceCube-250421A - IceCube observation of a high-energy neutrino candidate track-like event
  31. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  32. EP250421a: JinShan likely optical counterpart
  33. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  34. GRB 250421A: Fermi GBM Final Real-time Localization
  35. GRB 250419A: Liverpool Telescope observations
  36. GRB 250419A: LCO optical observation
  37. GRB 250419A: JinShan optical observations
  38. GRB 250419A: SVOM/VT optical continuous observations
  39. GRB 250419A: SVOM/C-GFT optical observations
  40. GRB 250419A: Swift/UVOT Follow up
  41. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  42. GRB 250419A: LCO optical afterglow multi-band observations
  43. GRB 250419A: Mondy and AbAO Optical Observations
  44. GRB 250419A: Liverpool Telescope observations
  45. GRB 250419A: AKO Optical Afterglow Detection
  46. GRB 250419A: MASTER optical afterglow observation
  47. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  48. GRB 250407A: rest-frame energetics from Konus-Wind observation
  49. GRB 250419A: Swift-XRT localisation
  50. GRB 250407A: GTC/OSIRIS+ spectroscopic redshift z = 1.36
  51. GRB 250419A: VLT/X-shooter spectroscopic redshift z = 0.845
  52. GRB 250419A: Swift-XRT refined Analysis
  53. GRB 250419A: GOTO optical counterpart detection
  54. GRB 250419A: KAIT optical afterglow observations
  55. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  56. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  57. GRB 250419A: SVOM detection of a soft burst
  58. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  59. EP250416a: Swift/XRT counterpart fading
  60. EP250416a: refined EP-WXT and EP-FXT analysis
  61. Konus-Wind detection of GRB 250403A
  62. EP20250416a: Swift/XRT counterpart detection
  63. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  64. IceCube-250416A: DDOTI Optical Observations
  65. EP250416a: Gemini South-GMOS optical counterpart
  66. EP250225a: SVOM/VT optical brightening
  67. SVOM/sb25041603 is not a GRB
  68. EP250416a: GSP optical upper limit
  69. EP250416a: Global MASTER-Net observations report
  70. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  71. EP250416a: Einstein Probe detection of an X-ray transient
  72. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  73. IceCube-250416A: Global MASTER-Net observations report
  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. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  78. SVOM/sb25041603: SVOM detection of an X-ray transient
  79. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  80. IceCube 250414.324: DDOTI Optical Observations
  81. GRB 250413A: AstroSat CZTI detection
  82. EP250304a: ATCA radio observations
  83. GRB 250412A: AstroSat CZTI detection
  84. EP250404a: Nanshan 0.43m Telescope optical observatios
  85. Fermi trigger No 766148493: Global MASTER-Net observations report
  86. Fermi trigger No 766173972: Global MASTER-Net observations report
  87. GRB 250411A: DDOTI Optical Observations
  88. Fermi GRB 250411A: Global MASTER-Net observations report
  89. GRB 250411A: Fermi GBM Final Real-time Localization
  90. GRB 250407A: Continued KAIT/Nickel optical observations
  91. GRB 250314A: e-MERLIN observations
  92. GRB 250407A: Mondy and AbAO Optical Observations
  93. EP250227a: Further NOT optical observations
  94. GRB 250320B: cubesat Avion detection
  95. IceCube-250406A: Swift-XRT observations
  96. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  97. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  98. IPN triangulation of GRB 250407A
  99. EP250407a: Global MASTER-Net observations report
  100. GRB 250407A: LCO detection of a fading optical counterpart

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
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