Skip to main content
New! Browse Circulars by Event, Advanced Search, Sample Codes, Schema Release. 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"

28714 results found.

  1. EP250416a: Global MASTER-Net observations report
  2. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  3. GRB 250413A: AstroSat CZTI detection
  4. EP250304a: ATCA radio observations
  5. EP250404a: Nanshan 0.43m Telescope optical observatios
  6. GRB 250411A: DDOTI Optical Observations
  7. Fermi GRB 250411A: Global MASTER-Net observations report
  8. GRB 250407A: Continued KAIT/Nickel optical observations
  9. GRB 250314A: e-MERLIN observations
  10. GRB 250407A: Mondy and AbAO Optical Observations
  11. EP250227a: Further NOT optical observations
  12. GRB 250320B: cubesat Avion detection
  13. IceCube-250406A: Swift-XRT observations
  14. IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
  15. IPN triangulation of GRB 250407A
  16. EP250407a: Global MASTER-Net observations report
  17. GRB 250407A: LCO detection of a fading optical counterpart
  18. Fermi-LAT gamma-ray observations of IceCube-250406A
  19. EP250407a: Swift-XRT observations
  20. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  21. Konus-Wind detection of GRB 250407A
  22. GRB 250407A: SVOM/GRM observation of a bright long burst
  23. GRB 250407A: EP-WXT afterglow detection
  24. EP250407a: EP-WXT detection of a fast X-ray transient
  25. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  26. GRB 250407A: KAIT Optical Afterglow Candidate
  27. IceCube-250406A: No candidates from the Zwicky Transient Facility
  28. GRB 250407A: Fermi GBM Detection
  29. GRB 250407A: Swift-XRT afterglow detection
  30. Fermi GRB 250407A: Global MASTER-Net observations report
  31. GRB 250407A: Swift ToO observations
  32. GRB 250407A: SRG/ART-XC afterglow detection
  33. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  34. Konus-Wind detection of GRB 250406B (short/hard)
  35. IPN triangulation of GRB 250406B (short/hard)
  36. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  37. GRB 250406A: AstroSat CZTI detection
  38. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  39. Fermi GRB 250406A: Global MASTER-Net observations report
  40. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  41. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  42. GRB 250404A / EP250404a: RC500 INASAN-Kislovodsk optical upper limit
  43. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  44. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  45. Konus-Wind detection of GRB 250404A / EP250404a
  46. GRB 250404A / EP250404a: Mondy optical observations
  47. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  48. GRB 250404A / EP250404a: GMG spectroscopic redshift at z ~ 2.627
  49. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  50. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  51. EP250402a: Optical upper limit with PD 1.3m observations
  52. GRB 250404A / EP250404a: NOT optical observations
  53. GRB 250403A: AstroSat CZTI detection
  54. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  55. EP250404a: REM optical/NIR observations
  56. EP250404a: Seimei/TriCCS optical counterpart detection
  57. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  58. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  59. EP250404a: LCO optical counterpart detection
  60. Fermi GRB 250404A: Global MASTER-Net observations report
  61. GRB 250403A: Montarrenti Observatory optical detection
  62. EP250404a: Global MASTER-Net observations report
  63. GRB 250403A: KAIT optical observations
  64. EP250404a: AKO Optical Afterglow Detection
  65. EP250404a: LAST detection of optical counterpart
  66. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  67. EP250404a: Xinglong-2.16m spectroscopic redshift
  68. GRB 250403A: Fermi GBM observations
  69. GRB 250327B: VIRT Optical Upper Limit
  70. EP250404a: Mephisto multi-band optical detection
  71. GRB 250331C Swift-BAT refined analysis
  72. GRB 250331B Swift-BAT refined analysis
  73. GRB 250330A Swift-BAT refined analysis
  74. EP250321A: J band upper limit by SYSU 80cm telescope
  75. EP250404a: BOOTES-4/JGT optical afterglow detection
  76. EP250404a: Nanshan/HMT optical counterpart detection
  77. EP250404a: Einstein Probe detection of an X-ray transient
  78. GRB 250402A: Mondy optical observations
  79. GRB 250403A: Swift/UVOT Detection
  80. GRB 250402A: Swift/UVOT Upper Limits
  81. EP250402a: Optical upper limit with Kinder observations
  82. GRB 250403A: SVOM/VT optical observation
  83. GRB 250403A: REM NIR afterglow detection
  84. GRB 250403A: LCO optical counterpart detection
  85. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  86. GRB 250403A: JinShan optical observations
  87. GRB 250402A: EP-FXT afterglow detection
  88. GRB 250403A: Optical counterpart detection by LCO.
  89. EP250402a: EP-FXT follow-up observations
  90. GRB 250403A: Swift-XRT observations
  91. GRB 250322A: 10 GHz VLA radio upper limits
  92. Fermi GRB 250403A: Global MASTER-Net observations report
  93. GRB 250403A: GOTO optical counterpart follow-up observations
  94. GRB 250402A: NUTTelA-TAO Early Optical Limits
  95. GRB 250403A: GMG Optical Observation
  96. GRB 250403A: 1.6m Mephisto multi-band optical detection
  97. GRB 250402A: Fermi GBM Observation
  98. GRB 250403A: SVOM/C-GFT optical observations
  99. GRB 250403A: GOTO detection of the optical afterglow
  100. GRB 250402A: Swift-XRT observations

Advanced

Download all Circulars as a .tar.gz archive:
Looking for U.S. government information and services? Visit USA.gov