Skip to main content
Circulars over Kafka event name backfill. 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').
  1. EP250416a: Swift/XRT counterpart fading
  2. EP250416a: refined EP-WXT and EP-FXT analysis
  3. Konus-Wind detection of GRB 250403A
  4. EP20250416a: Swift/XRT counterpart detection
  5. GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
  6. IceCube-250416A: DDOTI Optical Observations
  7. EP250416a: Gemini South-GMOS optical counterpart
  8. EP250225a: SVOM/VT optical brightening
  9. SVOM/sb25041603 is not a GRB
  10. EP250416a: GSP optical upper limit
  11. EP250416a: Global MASTER-Net observations report
  12. Fermi Gamma-ray Burst Monitor trigger 766505186/250416588 (GRB 250416A) is not a GRB
  13. EP250416a: Einstein Probe detection of an X-ray transient
  14. IceCube-250416A - IceCube observation of a high-energy neutrino candidate track-like event
  15. IceCube-250416A: Global MASTER-Net observations report
  16. Fermi Gamma-ray Burst Monitor trigger 766511207/250416657 is not a GRB
  17. GRB 250416B: Fermi GBM Final Real-time Localization
  18. GRB 250416A: Fermi GBM Final Real-time Localization
  19. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  20. SVOM/sb25041603: SVOM detection of an X-ray transient
  21. Fermi Gamma-ray Burst Monitor trigger 766474855/250416237 is not a GRB
  22. IceCube 250414.324: DDOTI Optical Observations
  23. GRB 250413A: AstroSat CZTI detection
  24. EP250304a: ATCA radio observations
  25. GRB 250412A: AstroSat CZTI detection
  26. EP250404a: Nanshan 0.43m Telescope optical observatios
  27. Fermi trigger No 766148493: Global MASTER-Net observations report
  28. Fermi trigger No 766173972: Global MASTER-Net observations report
  29. GRB 250411A: DDOTI Optical Observations
  30. Fermi GRB 250411A: Global MASTER-Net observations report
  31. GRB 250411A: Fermi GBM Final Real-time Localization
  32. GRB 250407A: Continued KAIT/Nickel optical observations
  33. GRB 250314A: e-MERLIN observations
  34. GRB 250407A: Mondy and AbAO Optical Observations
  35. EP250227a: Further NOT optical observations
  36. GRB 250320B: cubesat Avion detection
  37. IceCube-250406A: Swift-XRT observations
  38. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  39. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
  40. IPN triangulation of GRB 250407A
  41. EP250407a: Global MASTER-Net observations report
  42. GRB 250407A: LCO detection of a fading optical counterpart
  43. Fermi-LAT gamma-ray observations of IceCube-250406A
  44. EP250407a: Swift-XRT observations
  45. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  46. Konus-Wind detection of GRB 250407A
  47. GRB 250407A: SVOM/GRM observation of a bright long burst
  48. GRB 250407A: EP-WXT afterglow detection
  49. EP250407a: EP-WXT detection of a fast X-ray transient
  50. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  51. GRB 250407A: KAIT Optical Afterglow Candidate
  52. IceCube-250406A: No candidates from the Zwicky Transient Facility
  53. GRB 250407A: Fermi GBM Detection
  54. GRB 250407A: Swift-XRT afterglow detection
  55. Fermi GRB 250407A: Global MASTER-Net observations report
  56. GRB 250407A: Swift ToO observations
  57. GRB 250407A: SRG/ART-XC afterglow detection
  58. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  59. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  60. Konus-Wind detection of GRB 250406B (short/hard)
  61. IPN triangulation of GRB 250406B (short/hard)
  62. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  63. GRB 250407A: Fermi GBM Final Real-time Localization
  64. IceCube-250406A - IceCube observation of a high-energy neutrino candidate track-like event
  65. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  66. IceCube 250406.951: DDOTI Optical Observations
  67. GRB 250406A: AstroSat CZTI detection
  68. IceCube Alert 250406.95: Global MASTER-Net observations report
  69. Fermi trigger No 765663719: Global MASTER-Net observations report
  70. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  71. Fermi GRB 250406A: Global MASTER-Net observations report
  72. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  73. GRB 250406A: Fermi GBM Final Real-time Localization
  74. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  75. Fermi trigger No 765619921: Global MASTER-Net observations report
  76. Fermi Gamma-ray Burst Monitor trigger 765619921/250406342 is not a GRB
  77. GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit
  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:
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