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').
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"

24592 results found.

  1. GRB 250419A: Mondy and AbAO Optical Observations
  2. GRB 250419A: AKO Optical Afterglow Detection
  3. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  4. GRB 250419A: Swift-XRT refined Analysis
  5. GRB 250419A: KAIT optical afterglow observations
  6. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  7. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  8. GRB 250419A: SVOM detection of a soft burst
  9. EP250416a: Swift/XRT counterpart fading
  10. EP20250416a: Swift/XRT counterpart detection
  11. IceCube-250416A: DDOTI Optical Observations
  12. EP250416a: Gemini South-GMOS optical counterpart
  13. SVOM/sb25041603 is not a GRB
  14. EP250416a: GSP optical upper limit
  15. EP250416a: Einstein Probe detection of an X-ray transient
  16. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  17. SVOM/sb25041603: SVOM detection of an X-ray transient
  18. IceCube 250414.324: DDOTI Optical Observations
  19. GRB 250413A: AstroSat CZTI detection
  20. EP250304a: ATCA radio observations
  21. EP250404a: Nanshan 0.43m Telescope optical observatios
  22. GRB 250411A: DDOTI Optical Observations
  23. Fermi GRB 250411A: Global MASTER-Net observations report
  24. GRB 250407A: Continued KAIT/Nickel optical observations
  25. GRB 250314A: e-MERLIN observations
  26. GRB 250407A: Mondy and AbAO Optical Observations
  27. EP250227a: Further NOT optical observations
  28. GRB 250320B: cubesat Avion detection
  29. IceCube-250406A: Swift-XRT observations
  30. GRB 250407A: LCO detection of a fading optical counterpart
  31. Fermi-LAT gamma-ray observations of IceCube-250406A
  32. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube
  33. GRB 250407A: SVOM/GRM observation of a bright long burst
  34. GRB 250407A: EP-WXT afterglow detection
  35. EP250407a: EP-WXT detection of a fast X-ray transient
  36. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  37. GRB 250407A: KAIT Optical Afterglow Candidate
  38. IceCube-250406A: No candidates from the Zwicky Transient Facility
  39. GRB 250407A: Fermi GBM Detection
  40. GRB 250407A: Swift-XRT afterglow detection
  41. GRB 250407A: SRG/ART-XC afterglow detection
  42. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  43. IceCube 250406A: DDOTI Optical Observations of the Refined Position
  44. IPN triangulation of GRB 250406B (short/hard)
  45. GRB 250407A: BALROG localization (Fermi Trigger 765733706 / GRB 250407659)
  46. IceCube 250406.951: COLIBRÍ/DDRAGO Optical Upper Limit
  47. IceCube 250406.951: DDOTI Optical Observations
  48. GRB 250406A: AstroSat CZTI detection
  49. EP250404a: Multi-band Optical Observations from UCAS-70 and XL-C14
  50. GRB 250404A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  51. EP250404a / GRB 250404A: Montarrenti Observatory optical observations
  52. GRB 250404A / EP250404a: SVOM/GWAC-F60 and F50 observations
  53. EP250404a / GRB 250404A: J band observations by SYSU 80cm telescope
  54. Konus-Wind detection of GRB 250404A / EP250404a
  55. EP250404a: refined analysis of the EP-WXT and EP-FXT observations
  56. GRB 250404A / EP250404a: Leavitt Observatory optical counterpart detection
  57. GRB 250402A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  58. EP250402a: Optical upper limit with PD 1.3m observations
  59. GRB 250404A / EP250404a: NOT optical observations
  60. GRB 250331D: Swift-XRT afterglow detection
  61. GRB 250404B: AstroSat CZTI detection of a short burst
  62. EP250404a: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
  63. EP250404a: REM optical/NIR observations
  64. EP250404a: Seimei/TriCCS optical counterpart detection
  65. EP250404A: COLIBRÍ/DDRAGO Optical Observations
  66. EP250404A / GRB250404A: Ondrejov D50 optical afterglow detection
  67. EP250404a: LCO optical counterpart detection
  68. EP250404a: Xinglong decaying optical counterpart
  69. GRB 250403A: Montarrenti Observatory optical detection
  70. GRB 250404A: Fermi GBM Detection
  71. GRB 250403A: KAIT optical observations
  72. EP250404a: AKO Optical Afterglow Detection
  73. EP250404a: LAST detection of optical counterpart
  74. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  75. GRB 250403A: Fermi GBM observations
  76. GRB 250327B: VIRT Optical Upper Limit
  77. EP250404a: Mephisto multi-band optical detection
  78. GRB 250331C Swift-BAT refined analysis
  79. GRB 250331B Swift-BAT refined analysis
  80. GRB 250330A Swift-BAT refined analysis
  81. EP250321A: J band upper limit by SYSU 80cm telescope
  82. EP250404a: Nanshan/HMT optical counterpart detection
  83. EP250404a: Einstein Probe detection of an X-ray transient
  84. GRB 250403A: Swift/UVOT Detection
  85. GRB 250402A: Swift/UVOT Upper Limits
  86. EP250402a: Optical upper limit with Kinder observations
  87. GRB 250403A: REM NIR afterglow detection
  88. GRB 250403A: LCO optical counterpart detection
  89. IceCube-250330A: MASTER detection of PKS 2032+107 blazar flare with Zhirkov effect
  90. GRB 250403A: JinShan optical observations
  91. GRB 250403A: Optical counterpart detection by LCO.
  92. EP250402a: EP-FXT follow-up observations
  93. GRB 250403A: Swift-XRT observations
  94. GRB 250322A: 10 GHz VLA radio upper 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 250402A: Swift-XRT observations
  100. GRB250402A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart

Advanced

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