Skip to main content
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. EP250416a: Global MASTER-Net observations report
  2. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  3. EP250416a: Einstein Probe detection of an X-ray transient
  4. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  5. IceCube-250416A: Global MASTER-Net observations report
  6. Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
  7. GRB 250416B: Fermi GBM Final Real-time Localization
  8. GRB 250416A: Fermi GBM Final Real-time Localization
  9. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  10. SVOM/sb25041603: SVOM detection of an X-ray transient
  11. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  12. IceCube 250414.324: DDOTI Optical Observations
  13. GRB 250413A: AstroSat CZTI detection
  14. EP250304a: ATCA radio observations
  15. GRB 250412A: AstroSat CZTI detection
  16. EP250404a: Nanshan 0.43m Telescope optical observatios
  17. Fermi trigger No 766148493: Global MASTER-Net observations report
  18. Fermi trigger No 766173972: Global MASTER-Net observations report
  19. GRB 250411A: DDOTI Optical Observations
  20. Fermi GRB 250411A: Global MASTER-Net observations report
  21. GRB 250411A: Fermi GBM Final Real-time Localization
  22. GRB 250407A: Continued KAIT/Nickel optical observations
  23. GRB 250314A: e-MERLIN observations
  24. GRB 250407A: Mondy and AbAO Optical Observations
  25. EP250227a: Further NOT optical observations
  26. GRB 250320B: cubesat Avion detection
  27. IceCube-250406A: Swift-XRT observations
  28. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  29. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  30. IPN triangulation of GRB 250407A
  31. EP250407a: Global MASTER-Net observations report
  32. GRB 250407A: LCO detection of a fading optical counterpart
  33. Fermi-LAT gamma-ray observations of IceCube-250406A
  34. EP250407a: Swift-XRT observations
  35. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  36. Konus-Wind detection of GRB 250407A
  37. GRB 250407A: SVOM/GRM observation of a bright long burst
  38. GRB 250407A: EP-WXT afterglow detection
  39. EP250407a: EP-WXT detection of a fast X-ray transient
  40. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  41. GRB 250407A: KAIT Optical Afterglow Candidate
  42. IceCube-250406A: No candidates from the Zwicky Transient Facility
  43. GRB 250407A: Fermi GBM Detection
  44. GRB 250407A: Swift-XRT afterglow detection
  45. Fermi GRB 250407A: Global MASTER-Net observations report
  46. GRB 250407A: Swift ToO observations
  47. GRB 250407A: SRG/ART-XC afterglow detection
  48. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  49. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  50. Konus-Wind detection of GRB 250406B (short/hard)
  51. IPN triangulation of GRB 250406B (short/hard)
  52. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  53. GRB 250407A: Fermi GBM Final Real-time Localization
  54. IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event
  55. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  56. IceCube 250406.951: DDOTI Optical Observations
  57. GRB 250406A: AstroSat CZTI detection
  58. IceCube Alert 250406.95: Global MASTER-Net observations report
  59. Fermi trigger No 765663719: Global MASTER-Net observations report
  60. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  61. Fermi GRB 250406A: Global MASTER-Net observations report
  62. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  63. GRB 250406A: Fermi GBM Final Real-time Localization
  64. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  65. Fermi trigger No 765619921: Global MASTER-Net observations report
  66. Fermi Gamma-ray Burst Monitor trigger 765619921/250406342 is not a GRB
  67. GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit
  68. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  69. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  70. Konus-Wind detection of GRB 250404A / EP250404a
  71. GRB 250404A / EP250404a: Mondy optical observations
  72. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  73. GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
  74. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  75. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  76. EP250402a: Optical upper limit with PD 1.3m observations
  77. GRB 250404A / EP250404a: NOT optical observations
  78. GRB 250331D: Swift-XRT afterglow detection
  79. GRB 250404B: AstroSat CZTI detection of a short burst
  80. GRB 250403A: AstroSat CZTI detection
  81. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  82. EP250404a: REM optical/NIR observations
  83. EP250404a: Seimei/TriCCS optical counterpart detection
  84. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  85. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  86. EP250404a: LCO optical counterpart detection
  87. Fermi GRB 250404A: Global MASTER-Net observations report
  88. EP250404a: Xinglong decaying optical counterpart
  89. GRB 250403A: Montarrenti Observatory optical detection
  90. GRB 250404A: Fermi GBM Detection
  91. EP250404a: Global MASTER-Net observations report
  92. GRB 250403A: KAIT optical observations
  93. EP250404a: AKO Optical Afterglow Detection
  94. EP250404a: LAST detection of optical counterpart
  95. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  96. EP250404a: Xinglong-2.16m spectroscopic redshift
  97. GRB 250403A: Fermi GBM observations
  98. GRB 250327B: VIRT Optical Upper Limit
  99. EP250404a: Mephisto multi-band optical detection
  100. GRB 250331C Swift-BAT refined analysis

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