Skip to main content
Updates to LVK & CHIME Notices, Schema v7.2.3! 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"

45431 results found.

  1. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
  2. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  3. GRB 250610A: Fermi GBM Final Real-time Localization
  4. GRB 250605A: Swift-BAT refined analysis
  5. EP250610a: SVOM/VT optical upper limit
  6. EP250610a: REM optical/NIR observations
  7. GRB 250609A: Fermi GBM Observation
  8. GRBAlpha reentry on June 9, 2025
  9. EP250610a: Swift-XRT counterpart detection
  10. EP250610a: COLIBRÍ optical upper limit
  11. EP250610a: Einstein Probe detection of an X-ray transient
  12. Fermi trigger No 771072240: Global MASTER-Net observations report
  13. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  14. GRB 250605A: Swift/UVOT Upper Limits
  15. The EP-WXT trigger 01709178283 is likely a flaring star
  16. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  17. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  18. GRB 250527C: CrAO Optical Upper Limit
  19. GRB 250609A: Fermi GBM Final Real-time Localization
  20. GRB 250607A: SVOM/GRM observation of a long burst
  21. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  22. The EP-WXT trigger 01709178244 is likely a flaring star
  23. GRB 250607A: Fermi GBM Final Localization
  24. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  25. The EP-WXT trigger 01709178069 is likely a flaring star
  26. GRB 250605A: SVOM/VT optical upper limit
  27. GRB 250605A: Swift-XRT refined Analysis
  28. EP/WXT 01709177873: GOTO observations confirm stellar variability
  29. GRB 250605A: Enhanced Swift-XRT position
  30. Fermi GRB 250606A: Global MASTER-Net observations report
  31. GRB 250606A: Fermi GBM Final Real-time Localization
  32. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  33. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  34. GRB 250602A: GECAM detection
  35. Fermi trigger No 770867684: Global MASTER-Net observations report
  36. The EP-WXT trigger 01709177873 is likely a flaring star
  37. GRB 250605A: LT optical observations
  38. GRB 250605A: Swift detection of a burst
  39. Swift GRB250605.79: Global MASTER-Net observations report
  40. Konus-Wind detection of GRB 250601A
  41. IPN triangulation of GRB 250404B
  42. IPN triangulation of GRB 250529A
  43. The EP-WXT trigger 01709177837 is likely a flaring star
  44. Fermi Gamma-ray Burst Monitor trigger 770470765/250601486 is not a GRB
  45. GRB 250601A: PRIME H band upper limit.
  46. GRB 250530A: SVOM/GRM analysis
  47. GRB 250601A: PRIME J band upper limit.
  48. Fermi Gamma-ray Burst Monitor trigger 770675211/250603852 is not a GRB
  49. GRB 250601A: VLT/FORS2 Optical Observation
  50. GRB 250601A: Fermi GBM Observation
  51. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  52. GRB 250603A: Swift/UVOT Upper Limits
  53. GRB 250603A: Swift-XRT refined Analysis
  54. Fermi trigger No 770638414: Global MASTER-Net observations report
  55. GRB 250603A: Enhanced Swift-XRT position
  56. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  57. Swift GRB250603.05: Global MASTER-Net observations report
  58. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  59. GRB 250602A: Fermi GBM Observation
  60. GRB 250602A: Fermi-LAT detection
  61. GRB 250602A: DDOTI Optical Upper Limit
  62. GRB 250530C: Swift-BAT refined analysis
  63. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  64. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  65. GRB 250601A: Swift/XRT candidate afterglow
  66. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  67. GRB 250601A: Swift-XRT observations
  68. Fermi GRB 250601A: Global MASTER-Net observations report
  69. GRB 250602A: Fermi GBM Final Real-time Localization
  70. Fermi trigger No 770470765: Global MASTER-Net observations report
  71. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  72. GRB 250601A: Swift ToO observations
  73. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  74. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  75. GRB 250601A: Fermi GBM Final Real-time Localization
  76. EP#01709177494: SVOM/VT optical observations
  77. Fermi GRB 250531A: Global MASTER-Net observations report
  78. GRB 250531A: Fermi GBM Final Real-time Localization
  79. EP#01709177494: Swift-XRT counterpart detection of known source
  80. GRB 250530C: BOOTES-7 optical upper limit
  81. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  82. GRB 250530C: Swift-XRT refined Analysis
  83. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  84. Swift GRB 250530C: Global MASTER-Net observations report
  85. GRB 250530C: Enhanced Swift-XRT position
  86. GRB 250530C: Swift detection of a burst
  87. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  88. GRB 250530A: EP-FXT counterpart detection
  89. GRB 250530A: SVOM/VT optical upper limit
  90. Fermi Gamma-ray Burst Monitor trigger 770296643/250530470 is not a GRB
  91. GRB 250530B: Fermi GBM Final Real-time Localization
  92. GRB 250530A: Swift-XRT counterpart detection
  93. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  94. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  95. GRB 250530A: SVOM detection of a burst
  96. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  97. GRB 250527C: Swift/UVOT Upper Limits
  98. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  99. EP J1350.0-8622: EP-FXT follow-up observation
  100. GRB 250529B: Fermi GBM Final Real-time Localization

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
Questions or comments?
Contact GCN directly.
Have you found a bug in GCN?
Open an issue.
Want to contribute code to GCN?
Get involved on GitHub.

gcn.nasa.gov

A service of the Astrophysics Science Division at NASA Goddard Space Flight Center

Looking for U.S. government information and services? Visit USA.gov