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"

24598 results found.

  1. GRB 250502A: Montarrenti Observatory optical detection
  2. GRB 250502A: Swift-XRT afterglow detection
  3. GRB 250502A: NOT optical observations
  4. GRB 250502B: AstroSat CZTI detection
  5. GRB 250502A: AKO Optical Afterglow Detection
  6. GRB 250502A: LCO optical counterpart detection
  7. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  8. GRB 250407A: VZLUSAT-2 detection
  9. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  10. GRB 250502B: DDOTI Optical Observations
  11. GRB 250430A: Swift-XRT refined Analysis
  12. GRB 250502A: Early optical counterpart detection by LCO.
  13. GRB 250430A: Swift/UVOT Detection
  14. GRB 250502A: TRT optical afterglow confirmation
  15. GRB 250430A: Enhanced Swift-XRT position
  16. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  17. GRB 250502A: SVOM detection of a burst
  18. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  19. GRB 250430A: KAIT optical observations
  20. GRB 250430A / EP250430a: J-band upper limits with WINTER
  21. GRB 250430A: NUTTelA-TAO Early Measurements
  22. GRB 250430A: DDOTI Optical Observations
  23. GRB 250430A: Leavitt Observatory optical upper limit
  24. GRB 250430A: Bassano Bresciano Observatory upper limit
  25. GRB 250430A : MITSuME Akeno optical upper limits
  26. SVOM/sb25043004: EP-FXT observations
  27. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  28. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  29. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  30. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  31. GRB 250430A: AKO Optical Afterglow Detection
  32. GRB 250430A: Kanata optical upper limit
  33. EP 250427A: Optical counterpart detection by LCO.
  34. GRB 250430A: Swift detection of a burst with optical counterpart
  35. EP250427a/GRB250427A: HCT optical follow-up
  36. SVOM/sb25043004: SVOM detection of a X-ray transient
  37. EP250428b: GROWTH-India telescope optical upper limit
  38. EP250428b: SAO RAS optical upper limit
  39. EP250428b: LAST optical upper limit
  40. GRB 250427A: Swift/UVOT Detection
  41. EP250428b: Global MASTER-Net observations report
  42. EP250428b: Einstein Probe detection of a fast X-ray transient
  43. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  44. EP250427a: Lesedi optical counterpart detection
  45. EP250427A: COLIBRÍ Continuing Optical Observations
  46. GRB250427A/EP250427a GIT optical afterglow detection:
  47. EP250427a: LT optical counterpart detection
  48. GRB 250427A: Swift-XRT refined Analysis
  49. EP250427a / GRB 250427A: LCO optical counterpart detection
  50. EP250427a: REM optical/NIR afterglow detection
  51. GRB 250424A: LCO optical observation
  52. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  53. EP250427A: COLIBRÍ Optical Detection
  54. EP250427a: TRT optical counterpart detection
  55. EP250427a: Einstein Probe detection of a fast X-ray transient
  56. GRB 250424A: Swift-BAT refined analysis
  57. GRB 250424A: SVOM/GRM observation of a long burst
  58. GRB 250424A: PRIME near-infrared detection
  59. GRB 250424A: WINTER J-band detection
  60. GRB 250424A: EIRSAT-1 GMOD Detection
  61. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  62. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  63. GRB 250419A: Mondy Optical Observations
  64. GRB 250424A: Swift/UVOT Detection
  65. Fermi-LAT gamma-ray observations of IceCube-250421A
  66. GRB 250424A: Skynet Optical Observations
  67. GRB 250424A: Kilonova-Catcher optical afterglow detection
  68. GRB 250330B: GRBAlpha detection
  69. GRB 250424A: Swift-XRT refined Analysis
  70. GRB 250424A: Enhanced Swift-XRT position
  71. GRB 250424A: AstroSat CZTI detection of a bright long burst
  72. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  73. GRB 250424A: BlackGEM optical afterglow detection
  74. GRB 250424A: DDOTI Afterglow Detection
  75. GRB 250424A: REM optical/NIR afterglow detection
  76. GRB 250424A: Swift detection of a burst with an optical counterpart
  77. Swift GRB250424A: Global MASTER-Net OT detection
  78. LIGO/Virgo/KAGRA S250328ae: Subaru/PFS Spectroscopic Follow up and Candidates
  79. EP250421a: Nickel optical upper limit
  80. EP250421a: Upper limits from Fermi-GBM Observations
  81. SVOM/sb25042207: SVOM detection of an X-ray transient
  82. IceCube-250421A: DDOTI Detection of the LAST Candidate
  83. GRB 250419A: Mephisto Multi-band Optical Detection
  84. GRB 250419A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations.
  85. IC-250421A: LAST optical observations of the IceCube neutrino candidate
  86. EP250421a: NOT optical observations
  87. GRB 250419A: Optical Observations via Virtual Telescope Project
  88. EP250421a: REM optical upper limit
  89. EP250421A: COLIBRÍ Optical Upper Limit
  90. GRB 250419A: Mondy Continued Optical Observations
  91. GRB 250421B: AstroSat CZTI detection of a bright long burst
  92. EP250421a: Einstein Probe detection of an X-ray transient
  93. EP250421a: Mephisto optical counterpart confirmation
  94. IceCube-Cascade 250414A: Upper limits from a search for additional neutrino events in IceCube
  95. EP250421a: JinShan likely optical counterpart
  96. The EP-WXT trigger 01709135179: Kinder optical counterpart candidate
  97. GRB 250419A: LCO optical observation
  98. GRB 250419A: JinShan optical observations
  99. GRB 250419A: SVOM/C-GFT optical observations
  100. GRB 250419A: Swift/UVOT Follow up

Advanced

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