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"

43110 results found.

  1. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  2. GRB 250419A: SVOM detection of a soft burst
  3. Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
  4. EP250416a: Swift/XRT counterpart fading
  5. EP250416a: refined EP-WXT and EP-FXT analysis
  6. Konus-Wind detection of GRB 250403A
  7. EP20250416a: Swift/XRT counterpart detection
  8. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  9. IceCube-250416A: DDOTI Optical Observations
  10. EP250416a: Gemini South-GMOS optical counterpart
  11. EP250225a: SVOM/VT optical brightening
  12. SVOM/sb25041603 is not a GRB
  13. EP250416a: GSP optical upper limit
  14. EP250416a: Global MASTER-Net observations report
  15. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  16. EP250416a: Einstein Probe detection of an X-ray transient
  17. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  18. IceCube-250416A: Global MASTER-Net observations report
  19. GRB 250416B: Fermi GBM Final Real-time Localization
  20. GRB 250416A: Fermi GBM Final Real-time Localization
  21. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  22. SVOM/sb25041603: SVOM detection of an X-ray transient
  23. IceCube 250414.324: DDOTI Optical Observations
  24. GRB 250413A: AstroSat CZTI detection
  25. EP250304a: ATCA radio observations
  26. GRB 250412A: AstroSat CZTI detection
  27. EP250404a: Nanshan 0.43m Telescope optical observatios
  28. Fermi trigger No 766148493: Global MASTER-Net observations report
  29. Fermi trigger No 766173972: Global MASTER-Net observations report
  30. GRB 250411A: DDOTI Optical Observations
  31. Fermi GRB 250411A: Global MASTER-Net observations report
  32. GRB 250411A: Fermi GBM Final Real-time Localization
  33. GRB 250407A: Continued KAIT/Nickel optical observations
  34. GRB 250314A: e-MERLIN observations
  35. GRB 250407A: Mondy and AbAO Optical Observations
  36. EP250227a: Further NOT optical observations
  37. GRB 250320B: cubesat Avion detection
  38. IceCube-250406A: Swift-XRT observations
  39. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  40. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  41. IPN triangulation of GRB 250407A
  42. EP250407a: Global MASTER-Net observations report
  43. GRB 250407A: LCO detection of a fading optical counterpart
  44. Fermi-LAT gamma-ray observations of IceCube-250406A
  45. EP250407a: Swift-XRT observations
  46. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  47. Konus-Wind detection of GRB 250407A
  48. GRB 250407A: SVOM/GRM observation of a bright long burst
  49. GRB 250407A: EP-WXT afterglow detection
  50. EP250407a: EP-WXT detection of a fast X-ray transient
  51. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  52. GRB 250407A: KAIT Optical Afterglow Candidate
  53. IceCube-250406A: No candidates from the Zwicky Transient Facility
  54. GRB 250407A: Fermi GBM Detection
  55. GRB 250407A: Swift-XRT afterglow detection
  56. Fermi GRB 250407A: Global MASTER-Net observations report
  57. GRB 250407A: Swift ToO observations
  58. GRB 250407A: SRG/ART-XC afterglow detection
  59. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  60. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  61. Konus-Wind detection of GRB 250406B (short/hard)
  62. IPN triangulation of GRB 250406B (short/hard)
  63. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  64. GRB 250407A: Fermi GBM Final Real-time Localization
  65. IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event
  66. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  67. IceCube 250406.951: DDOTI Optical Observations
  68. GRB 250406A: AstroSat CZTI detection
  69. IceCube Alert 250406.95: Global MASTER-Net observations report
  70. Fermi trigger No 765663719: Global MASTER-Net observations report
  71. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  72. Fermi GRB 250406A: Global MASTER-Net observations report
  73. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  74. GRB 250406A: Fermi GBM Final Real-time Localization
  75. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  76. Fermi trigger No 765619921: Global MASTER-Net observations report
  77. Fermi Gamma-ray Burst Monitor trigger 765619921/250406342 is not a GRB
  78. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  79. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  80. Konus-Wind detection of GRB 250404A / EP250404a
  81. GRB 250404A / EP250404a: Mondy optical observations
  82. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  83. GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
  84. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  85. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  86. EP250402a: Optical upper limit with PD 1.3m observations
  87. GRB 250404A / EP250404a: NOT optical observations
  88. GRB 250331D: Swift-XRT afterglow detection
  89. GRB 250404B: AstroSat CZTI detection of a short burst
  90. GRB 250403A: AstroSat CZTI detection
  91. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  92. EP250404a: REM optical/NIR observations
  93. EP250404a: Seimei/TriCCS optical counterpart detection
  94. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  95. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  96. EP250404a: LCO optical counterpart detection
  97. Fermi GRB 250404A: Global MASTER-Net observations report
  98. EP250404a: Xinglong decaying optical counterpart
  99. GRB 250403A: Montarrenti Observatory optical detection
  100. GRB 250404A: Fermi GBM Detection

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