Skip to main content
JSON Notices via Email, Kafka Cron Jobs, Submitter Profile, GCN is Hiring. See news and announcements

GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

28123 results found.

  1. GRB 250504A: EIRSAT-1 GMOD Detection
  2. GRB 250502A: Bassano Bresciano Observatory upper limit
  3. GRB 250506A: Xinglong 2.16m optical upper limit
  4. SVOM/sb25050601: EP-FXT observations
  5. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  6. GRB 250506A: REM optical/NIR upper limits
  7. GRB 250506A: Fermi GBM Observation
  8. GRB 250506A: Swift XRT observations and possible counterpart detection
  9. GRB 250506A: TRT optical observations
  10. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  11. GRB 250506A: SVOM detection of a burst
  12. GRB 250504A: Swift-BAT refined analysis
  13. GRB 250430A: Swift-BAT refined analysis
  14. GRB 250504A: Swift-XRT refined Analysis
  15. GRB 250504A: VLT/X-shooter upper limits
  16. GRB 250504A: REM optical/NIR observations
  17. GRB 250502A: REM optical/NIR observations
  18. GRB 250504A: MeerLICHT optical afterglow detection
  19. GRB 250504A: Fermi GBM Observation
  20. GRB 250504A: Enhanced Swift-XRT position
  21. Fermi GRB 250504A: Global MASTER-Net observations report
  22. GRB 250504A: Swift detection of a burst
  23. GRB 250502A: Swift/UVOT Follow up
  24. GRB 250502A: Mondy and Tien-Shan Optical Observations
  25. GRB 250502A: KAIT optical observations
  26. GRB 250502A: Montarrenti Observatory optical detection
  27. GRB 250502A: Swift-XRT afterglow detection
  28. GRB 250502A: NOT optical observations
  29. GRB 250502B: AstroSat CZTI detection
  30. GRB 250502A: AKO Optical Afterglow Detection
  31. GRB 250502A: LCO optical counterpart detection
  32. GRB 250502A: Redshift from OSIRIS+/GTC z = 2.163
  33. GRB 250407A: VZLUSAT-2 detection
  34. Fermi-LAT Gamma-ray Observations of IceCube-250429A
  35. GRB 250502B: DDOTI Optical Observations
  36. GRB 250430A: Swift-XRT refined Analysis
  37. GRB 250502A: Early optical counterpart detection by LCO.
  38. GRB 250430A: Swift/UVOT Detection
  39. GRB 250502A: TRT optical afterglow confirmation
  40. GRB 250430A: Enhanced Swift-XRT position
  41. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  42. GRB 250502A: SVOM detection of a burst
  43. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  44. GRB 250430A: KAIT optical observations
  45. GRB 250430A / EP250430a: J-band upper limits with WINTER
  46. GRB 250430A: NUTTelA-TAO Early Measurements
  47. GRB 250430A: DDOTI Optical Observations
  48. GRB 250430A: Leavitt Observatory optical upper limit
  49. GRB 250430A: Bassano Bresciano Observatory upper limit
  50. GRB 250430A : MITSuME Akeno optical upper limits
  51. SVOM/sb25043004: EP-FXT observations
  52. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  53. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  54. IceCube-250429A: Upper limits from a search for additional neutrino events in IceCube
  55. IceCube-250426A: Upper limits from a search for additional neutrino events in IceCube
  56. GRB 250430A: AKO Optical Afterglow Detection
  57. GRB 250430A: Kanata optical upper limit
  58. EP 250427A: Optical counterpart detection by LCO.
  59. GRB 250430A: Swift detection of a burst with optical counterpart
  60. EP250427a/GRB250427A: HCT optical follow-up
  61. SVOM/sb25043004: SVOM detection of a X-ray transient
  62. EP250428b: GROWTH-India telescope optical upper limit
  63. EP250428b: SAO RAS optical upper limit
  64. EP250428b: LAST optical upper limit
  65. GRB 250427A: Swift/UVOT Detection
  66. EP250428b: Global MASTER-Net observations report
  67. EP250428b: Einstein Probe detection of a fast X-ray transient
  68. Fermi-LAT Gamma-ray Observations of IceCube-250426A
  69. EP250427a: Lesedi optical counterpart detection
  70. EP250427A: COLIBRÍ Continuing Optical Observations
  71. GRB250427A/EP250427a GIT optical afterglow detection:
  72. EP250427a: LT optical counterpart detection
  73. GRB 250427A: Swift-XRT refined Analysis
  74. EP250427a / GRB 250427A: LCO optical counterpart detection
  75. EP250427a: REM optical/NIR afterglow detection
  76. GRB 250424A: LCO optical observation
  77. GRB 250427A/ EP250427a: Fermi-GBM Sub-Threshold Detection
  78. EP250427A: COLIBRÍ Optical Detection
  79. EP250427a: TRT optical counterpart detection
  80. EP250427a: Einstein Probe detection of a fast X-ray transient
  81. GRB 250424A: Swift-BAT refined analysis
  82. GRB 250424A: SVOM/GRM observation of a long burst
  83. GRB 250424A: PRIME near-infrared detection
  84. GRB 250424A: WINTER J-band detection
  85. GRB 250424A: EIRSAT-1 GMOD Detection
  86. IceCube-250416A: Upper limits from a search for additional neutrino events in IceCube
  87. IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
  88. GRB 250419A: Mondy Optical Observations
  89. GRB 250424A: Swift/UVOT Detection
  90. Fermi-LAT gamma-ray observations of IceCube-250421A
  91. GRB 250424A: Skynet Optical Observations
  92. GRB 250424A: Kilonova-Catcher optical afterglow detection
  93. GRB 250330B: GRBAlpha detection
  94. GRB 250424A: Swift-XRT refined Analysis
  95. GRB 250424A: Enhanced Swift-XRT position
  96. GRB 250424A: AstroSat CZTI detection of a bright long burst
  97. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  98. GRB 250424A: BlackGEM optical afterglow detection
  99. GRB 250424A: DDOTI Afterglow Detection
  100. GRB 250424A: REM optical/NIR afterglow detection

Advanced

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