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"

24662 results found.

  1. EP250427a/GRB250427A: HCT optical follow-up
  2. SVOM/sb25043004: SVOM detection of a X-ray transient
  3. EP250428b: GROWTH-India telescope optical upper limit
  4. EP250428b: SAO RAS optical upper limit
  5. EP250428b: LAST optical upper limit
  6. GRB 250427A: Swift/UVOT Detection
  7. EP250428b: Global MASTER-Net observations report
  8. EP250428b: Einstein Probe detection of a fast X-ray transient
  9. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  10. EP250427a: Lesedi optical counterpart detection
  11. EP250427A: COLIBRÍ Continuing Optical Observations
  12. GRB250427A/EP250427a GIT optical afterglow detection:
  13. EP250427a: LT optical counterpart detection
  14. GRB 250427A: Swift-XRT refined Analysis
  15. EP250427a / GRB 250427A: LCO optical counterpart detection
  16. EP250427a: REM optical/NIR afterglow detection
  17. GRB 250424A: LCO optical observation
  18. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  19. EP250427A: COLIBRÍ Optical Detection
  20. EP250427a: TRT optical counterpart detection
  21. EP250427a: Einstein Probe detection of a fast X-ray transient
  22. GRB 250424A: Swift-BAT refined analysis
  23. GRB 250424A: SVOM/GRM observation of a long burst
  24. GRB 250424A: PRIME near-infrared detection
  25. GRB 250424A: WINTER J-band detection
  26. GRB 250424A: EIRSAT-1 GMOD Detection
  27. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  28. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  29. GRB 250419A: Mondy Optical Observations
  30. GRB 250424A: Swift/UVOT Detection
  31. Fermi-LAT gamma-ray observations of IceCube-250421A
  32. GRB 250424A: Skynet Optical Observations
  33. GRB 250424A: Kilonova-Catcher optical afterglow detection
  34. GRB 250330B: GRBAlpha detection
  35. GRB 250424A: Swift-XRT refined Analysis
  36. GRB 250424A: Enhanced Swift-XRT position
  37. GRB 250424A: AstroSat CZTI detection of a bright long burst
  38. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  39. GRB 250424A: BlackGEM optical afterglow detection
  40. GRB 250424A: DDOTI Afterglow Detection
  41. GRB 250424A: REM optical/NIR afterglow detection
  42. GRB 250424A: Swift detection of a burst with an optical counterpart
  43. Swift GRB250424A: Global MASTER-Net OT detection
  44. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  45. EP250421a: Nickel optical upper limit
  46. EP250421a: Upper limits from Fermi-GBM Observations
  47. SVOM/sb25042207: SVOM detection of an X-ray transient
  48. IceCube-250421A: DDOTI Detection of the LAST Candidate
  49. GRB 250419A: Mephisto Multi-band Optical Detection
  50. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  51. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  52. EP250421a: NOT optical observations
  53. GRB 250419A: Optical Observations via Virtual Telescope Project
  54. EP250421a: REM optical upper limit
  55. EP250421A: COLIBRÍ Optical Upper Limit
  56. GRB 250419A: Mondy Continued Optical Observations
  57. GRB 250421B: AstroSat CZTI detection of a bright long burst
  58. EP250421a: Einstein Probe detection of an X-ray transient
  59. EP250421a: Mephisto optical counterpart confirmation
  60. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  61. EP250421a: JinShan likely optical counterpart
  62. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  63. GRB 250419A: LCO optical observation
  64. GRB 250419A: JinShan optical observations
  65. GRB 250419A: SVOM/C-GFT optical observations
  66. GRB 250419A: Swift/UVOT Follow up
  67. GRB 250416C / EP250416a: SVOM/GRM observation of a burst
  68. GRB 250419A: LCO optical afterglow multi-band observations
  69. GRB 250419A: Mondy and AbAO Optical Observations
  70. GRB 250419A: AKO Optical Afterglow Detection
  71. Fermi-LAT Gamma-ray Observations of IceCube-250416A
  72. GRB 250419A: Swift-XRT refined Analysis
  73. GRB 250419A: KAIT optical afterglow observations
  74. GRB 250419A: SVOM/VT optical bright counterpart confirmation
  75. GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
  76. GRB 250419A: SVOM detection of a soft burst
  77. EP250416a: Swift/XRT counterpart fading
  78. EP20250416a: Swift/XRT counterpart detection
  79. IceCube-250416A: DDOTI Optical Observations
  80. EP250416a: Gemini South-GMOS optical counterpart
  81. SVOM/sb25041603 is not a GRB
  82. EP250416a: GSP optical upper limit
  83. EP250416a: Einstein Probe detection of an X-ray transient
  84. SVOM/sb25041603: SVOM/COLIBRÍ (FM-GFT) Upper Limit on the Optical Counterpart
  85. SVOM/sb25041603: SVOM detection of an X-ray transient
  86. IceCube 250414.324: DDOTI Optical Observations
  87. GRB 250413A: AstroSat CZTI detection
  88. EP250304a: ATCA radio observations
  89. EP250404a: Nanshan 0.43m Telescope optical observatios
  90. GRB 250411A: DDOTI Optical Observations
  91. Fermi GRB 250411A: Global MASTER-Net observations report
  92. GRB 250407A: Continued KAIT/Nickel optical observations
  93. GRB 250314A: e-MERLIN observations
  94. GRB 250407A: Mondy and AbAO Optical Observations
  95. EP250227a: Further NOT optical observations
  96. GRB 250320B: cubesat Avion detection
  97. IceCube-250406A: Swift-XRT observations
  98. GRB 250407A: LCO detection of a fading optical counterpart
  99. Fermi-LAT gamma-ray observations of IceCube-250406A
  100. IceCube-250406A: Upper limits from a search for additional neutrino events in IceCube

Advanced

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