Skip to main content
New! Browse Circulars by Event, Advanced Search, Sample Codes, Schema Release. 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"

18639 results found.

  1. GRB 250329B: Swift-XRT afterglow detection
  2. GRB 250330A: Swift detection of a burst
  3. Swift GRB250330.26: Global MASTER-Net observations report
  4. GRB 250329B: SVOM/C-GFT optical upper limit
  5. GRB 250329B: SVOM/VT optical upper limit
  6. GRB 250329A: Swift-XRT afterglow detection
  7. GRB 250328A: SVOM/C-GFT optical upper limit
  8. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  9. GRB 250327B: LCO optical counterpart detection
  10. GRB 250322A: GRANDMA/TNOT optical upper limits
  11. GRB 250327A: SVOM/VT upper limits on the XRT position
  12. GRB 250327B: Swift-XRT detection of the X-ray afterglow
  13. GRB 250327A: Swift-XRT refined Analysis
  14. FRB 20250316A: The sub-arcsecond localization of FRB 20250316A using CHIME/FRB Outriggers coincides with reported X-ray counterparts
  15. GRB 250327A: J-band observations with WINTER
  16. GRB 250327A: SVOM/VT optical candidate
  17. GRB 250327A: Fermi GBM observation
  18. Swift GRB 250327A: Global MASTER-Net observations report
  19. GRB 250327A: DDOTI Optical Observations
  20. GRB 250327A: COLIBRÍ optical upper limit
  21. GRB 250327A: Swift detection of a burst
  22. Konus-Wind detection of GRB 250322A (short)
  23. IPN triangulation of GRB 250322B
  24. Swift follow-up observations of FRB250316A and EP J120944.2+585060
  25. GRB 250322A: Swift-BAT refined analysis
  26. GRB 250322A: Swift/UVOT Upper Limits
  27. GRB 250321B: Swift-XRT observations
  28. GRB 250322A: Swift-XRT refined Analysis
  29. GRB 250322A: AstroSat CZTI detection of a short burst
  30. GRB250322A: STEP/T80S optical limits
  31. GRB 250322A: VLT optical observations
  32. GRB 250322A: VLT near-infrared observations
  33. GRB 250322A: NOT optical upper limits
  34. GRB 250322A: Enhanced Swift-XRT position
  35. GRB 250322A: MASTER optical observation
  36. GRB 250322A: Swift detection of a short burst
  37. EP250321a: refined analysis of the EP-WXT and EP-FXT observations
  38. GRB 250225B: GECAM-A detection
  39. GRB 250312A: GECAM-A detection
  40. GRB 250321B: Swift ToO observations
  41. GRB 250321A: Swift-BAT refined analysis
  42. GRB 250321A: Swift-XRT refined Analysis
  43. GRB 250320B: Fermi-LAT detection
  44. GRB 250321A: Swift/UVOT Upper Limits
  45. EP250321a: LCO optical counterpart detection
  46. EP250321a: Swift-XRT detection of an X-ray source
  47. Swift GRB 250321A: Global MASTER-Net observations report
  48. GRB 250321A: GOTO optical upper limits
  49. GRB 250321A: Swift-XRT localisation
  50. GRB 250321A: Fermi GBM Observation
  51. GRB 250321A: Swift detection of a burst
  52. GRB250312A: Swift/UVOT Upper Limits
  53. GRB 250317B: Swift-XRT observations
  54. GRB 250316A: Swift/UVOT Upper Limits
  55. GRB 250314A: REM optical/NIR upper limits
  56. GRB 250316A: AbAO AS-32 Optical Upper Limit
  57. GRB 250316A: Swift-XRT afterglow detection
  58. GRB 250316A: Fermi GBM Observation
  59. GRB 250316A: Swift-XRT observations
  60. GRB 250316A: Swift ToO observations
  61. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  62. GRB 250314A: EP-FXT afterglow detection
  63. GRB 250314A: Swift/UVOT Upper Limits
  64. GRB 250312B: GRBAlpha detection
  65. GRB 250314A: Swift XRT Detection
  66. GRB 250314A: NOT near-infrared candidate counterpart
  67. GRB 250312B: Fermi GBM Observation
  68. GRB 250313A: Swift-XRT observations
  69. Konus-Wind detection of GRB 250308A
  70. GRB 250313A: Fermi-LAT detection
  71. GRB 250313A: Swift ToO observations
  72. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  73. EP250304a: SVOM/VT optical observation
  74. EP250302a: Chandra X-ray Detection
  75. GRB 250312A: Swift-XRT refined Analysis
  76. GRB 250312A: Enhanced Swift-XRT position
  77. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  78. GRB 250226B: Fermi GBM Observation
  79. Swift GRB 250312A: Global MASTER-Net observations report
  80. GRB 250302A: Fermi GBM Observation
  81. GRB 250312A: Swift detection of a burst
  82. GRB 250223B: Fermi GBM Observation
  83. GRB 250311A: Swift-XRT observations
  84. GRB 250228A: Fermi GBM Observation
  85. GRB 230509B: 1.3m DFOT Optical observations
  86. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  87. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  88. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  89. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  90. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  91. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  92. EP250304a: Chandra detection
  93. GRB 250225B: Swift-BAT refined analysis
  94. GRB 250311A: Tiled Swift observations
  95. IPN triangulation of GRB 250308A (short)
  96. GRB 250309B: Swift-XRT refined Analysis
  97. GRB 250309B / AT2025dws: Swift-UVOT detection
  98. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  99. Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
  100. GRB 230509B: Tiled Swift observations

Advanced

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