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"

19630 results found.

  1. GRB 250424A: Swift-XRT refined Analysis
  2. GRB 250424A: Enhanced Swift-XRT position
  3. GRB 250424A: AstroSat CZTI detection of a bright long burst
  4. GRB 250424A: COLIBRÍ Detection of a Bright Optical Counterpart
  5. GRB 250424A: BlackGEM optical afterglow detection
  6. GRB 250424A: VLT/X-shooter spectroscopic redshift z = 0.310
  7. GRB 250424A: likely host galaxy
  8. GRB 250424A: DDOTI Afterglow Detection
  9. GRB 250424A: REM optical/NIR afterglow detection
  10. GRB 250424A: Swift detection of a burst with an optical counterpart
  11. Swift GRB 250424A: Global MASTER-Net observations report
  12. Swift GRB 250424A: Global MASTER-Net OT detection
  13. SVOM/sb25042207: XRT observations
  14. EP250421a: NOT optical observations
  15. EP250421a: Swift/XRT counterpart detection
  16. GRB 250419A: Swift/UVOT Follow up
  17. GRB 250419A: LCO optical afterglow multi-band observations
  18. GRB 250419A: Mondy and AbAO Optical Observations
  19. GRB 250419A: Swift-XRT localisation
  20. GRB 250419A: Swift-XRT refined Analysis
  21. EP250416a: Swift/XRT counterpart fading
  22. EP20250416a: Swift/XRT counterpart detection
  23. GRB 250407A: Mondy and AbAO Optical Observations
  24. IceCube-250406A: Swift-XRT observations
  25. IPN triangulation of GRB 250407A
  26. GRB 250407A: LCO detection of a fading optical counterpart
  27. EP250407a: Swift-XRT observations
  28. Konus-Wind detection of GRB 250407A
  29. GRB 250407A: SVOM/GRM observation of a bright long burst
  30. GRB 250407A: EP-WXT afterglow detection
  31. GRB 250407A: COLIBRÍ/DDRAGO Detection of the Optical Counterpart
  32. GRB 250407A: Fermi GBM Detection
  33. GRB 250407A: Swift-XRT afterglow detection
  34. GRB 250407A: Swift ToO observations
  35. GRB 250407A: SRG/ART-XC afterglow detection
  36. LIGO/Virgo/KAGRA S250331o: Upper limits from Swift/BAT-GUANO
  37. IPN triangulation of GRB 250406B (short/hard)
  38. GRB 250331D: Swift-XRT afterglow detection
  39. GRB 250403A: Montarrenti Observatory optical detection
  40. GRB 250402A: Swift/BAT-GUANO localization skymap of a burst
  41. GRB 250331C Swift-BAT refined analysis
  42. GRB 250331B Swift-BAT refined analysis
  43. GRB 250330A Swift-BAT refined analysis
  44. EP250321A: J band upper limit by SYSU 80cm telescope
  45. GRB 250403A: Swift/UVOT Detection
  46. GRB 250402A: Swift/UVOT Upper Limits
  47. GRB 250403A: LCO optical counterpart detection
  48. GRB 250402A: EP-FXT afterglow detection
  49. GRB 250403A: Swift-XRT observations
  50. GRB 250402A: Swift-XRT observations
  51. GRB 250225B: VLT host galaxy redshift z = 0.950
  52. GRB 250331C: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  53. GRB 250329B: Swift/UVOT Upper Limit
  54. GRB 250329A: Swift/UVOT Upper Limit
  55. GRB 250327B: Swift/UVOT Detection
  56. GRB 250327A: Swift/UVOT Upper Limits
  57. GRB250331D: AbAO optical observations
  58. GRB 250331D: Fermi GBM observation
  59. GRB 250331C: Swift/UVOT Upper Limits
  60. GRB 250331B: Swift/UVOT Upper Limits
  61. GRB 250331D: Swift-XRT observations
  62. GRB 250331C: Swift-XRT refined Analysis
  63. GRB 250331B: Swift-XRT refined Analysis
  64. GRB 250331B: Swift-XRT refined Analysis
  65. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Epoch 2)
  66. GRB 250327A Swift-BAT refined analysis
  67. GRB 250329B: CAHA 2.2m telescope optical limit
  68. GRB 250331D: Swift ToO observations
  69. Swift GRB 250331C: Global MASTER-Net observations report
  70. Swift GRB 250331B: Global MASTER-Net observations report
  71. GRB 250331D: Swift/BAT-GUANO arcminute localization of a burst during slew
  72. GRB 250331C: Enhanced Swift-XRT position
  73. GRB 250331B: Enhanced Swift-XRT position
  74. LIGO/Virgo/KAGRA S250328ae: Swift XRT observations, 34 possible X-ray sources
  75. GRB 250329B: Swift-XRT confirmation of fading
  76. GRB20250327B: 45th Parallel Observatory upper limit
  77. GRB 250328A: Swift/UVOT Detection
  78. GRB 250328A: Swift-XRT refined Analysis
  79. GRB 250330A: Fermi GBM Observation
  80. GRB 250331C: COLIBRÍ/DDRAGO optical upper limit
  81. GRB 250331B: COLIBRÍ/DDRAGO optical upper limit
  82. GRB 250331C: Prompt enhanced Swift-XRT position
  83. GRB 250331C: Swift detection of a burst
  84. GRB 250331B: Swift detection of a burst
  85. GRB 250330A: SVOM/VT optical upper limit
  86. GRB 250330A: BOOTES-7 early optical upper limit
  87. GRB 250330A: Swift/UVOT Upper Limits
  88. GRB 250330A: Swift-XRT afterglow detection
  89. GRB 250330A: Fermi GBM Final Localization
  90. GRB 250330A: Prompt Swift-XRT position
  91. GRB 250329B: Swift-XRT afterglow detection
  92. GRB 250330A: Swift detection of a burst
  93. Swift GRB250330.26: Global MASTER-Net observations report
  94. GRB 250329B: SVOM/C-GFT optical upper limit
  95. GRB 250329B: SVOM/VT optical upper limit
  96. GRB 250329A: Swift-XRT afterglow detection
  97. GRB 250328A: SVOM/C-GFT optical upper limit
  98. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  99. GRB 250327B: LCO optical counterpart detection
  100. GRB 250322A: GRANDMA/TNOT optical upper limits

Advanced

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