Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to https://gcn.nasa.gov.
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"
  1. IPN triangulation of GRB 210424B (short/hard)
  2. GRB 210323B: Swift-XRT observations
  3. Swift Trigger 1045571 is not a GRB
  4. GRB 210427A: GECAM detection
  5. GRB 210427A: BALROG localization (Fermi Trigger / GRB 210427206)
  6. Fermi GRB 210427A: Global MASTER-Net observations report
  7. GRB 210427A: Fermi GBM Final Real-time Localization
  8. GRB 210422B: Fermi GBM Final Localization
  9. GRB 210420B: Assy optical observations
  10. Fermi trigger No 640975205: Global MASTER-Net observations report
  11. GRB 210425A: GECAM detection
  12. GRB 210424.694: DDOTI Upper Limits on the Afterglow
  13. GRB 210422A: Swift-BAT refined analysis
  14. GRB 210424A: Fermi GBM Final Real-time Localization
  15. GRB 210420B: follow-up photometry of optical afterglow at INASAN/Simeiz
  16. GRB 210420B: Zeiss-1000 of Koshka optical observations
  17. GRB 210421A: Swift-BAT refined analysis
  18. GRB 210421B: Swift-XRT observations
  19. GRB 210421B: AstroSat CZTI detection
  20. GRB 210420B: continued Tautenburg observations
  21. GRB 210421A: GECAM detection
  22. GRB 210421B: AstroSat CZTI detection
  23. Swift GRB210422.74: Global MASTER-Net observations report
  24. GRB 210422A: Swift detection of a burst
  25. GRB 210421A: Swift/UVOT Upper Limits
  26. GRB 210420B: Correction to AST3-3 YaoAn magnitude
  27. GRB 210420B: follow-up photometry of the optical afterglow at Konkoly
  28. GRB 210421A: MITSuME Akeno optical upper limits
  29. GRB 210419B: AstroSat CZTI detection
  30. Fermi Gamma-ray Burst Monitor trigger 210421C is not a GRB
  31. GRB 210420B: Swift-BAT refined analysis
  32. GRB 210421B: Swift ToO observations
  33. GRB 210421B: Swift/BAT-GUANO detection and arcminute localization
  34. GRB 210420B: Swift-XRT refined Analysis
  35. GRB 210421A: Swift-XRT refined Analysis
  36. GRB 210421B: Correction of GRB Type to "Likely Long GRB"
  37. Fermi GRB 210421C: Global MASTER-Net observations report
  38. GRB 210420B: Montarrenti Observatory follow-up observations
  39. GRB 210421C: Fermi GBM Final Real-time Localization
  40. GRB 210421B: Fermi GBM Final Localization
  41. Fermi trigger No 640695289: Global MASTER-Net observations report
  42. GRB 210419C: Swift/UVOT Upper Limits
  43. GRB 210420B: Correction to DDOTI Magnitude
  44. GRB 210420B: Ondrejov D50 optical afterglow detection
  45. GRB 210421A: Enhanced Swift-XRT position
  46. GRB 210420B: RATIR Optical and NIR Observations
  47. GRB 210420B: Tautenburg observations
  48. GRB 210420B: Swift/UVOT Detection
  49. GRB 210420B: KAIT Optical Observations
  50. GRB 210413B: MITSuME Okayama optical upper limits
  51. GRB 210419C: MITSuME Akeno optical upper limits
  52. GRB 210420B: DDOTI Detection of the Afterglow
  53. GRB 210421A: DDOTI Upper Limit
  54. GRB 210419C: Swift-BAT refined analysis
  55. Fermi GRB 210420A: Global MASTER-Net observations report
  56. GRB 210420B: update on the BAT trigger time
  57. GRB 210420B: Redshift from GTC
  58. GRB 210420B: Multiband photometry from NOT
  59. GRB 210420B: Montarrenti Observatory optical afterglow detection
  60. Swift GRB 210421A: Global MASTER-Net observations report
  61. GRB 210421A: Swift detection of a burst
  62. GRB 210420B: AST3-3 YaoAn Optical Observation
  63. GRB 210420B: BOOTES-4/MET optical afterglow detection
  64. GRB 210420B: Optical observations
  65. GRB 210420B: MASTER optical counterpart detection
  66. GRB 210420B: Swift detection of a burst
  67. GRB 210419C: RATIR Optical and NIR Upper Limits
  68. GRB 210419C: Montarrenti Observatory Upper Limit
  69. GRB 210419A: Swift/UVOT Upper Limits
  70. GRB 210419C: KAIT Optical Upper Limit
  71. GRB 210419C: Enhanced Swift-XRT position
  72. GRB 210419A: Swift-BAT refined analysis
  73. GRB 210420A: Fermi GBM Final Real-time Localization
  74. Swift GRB210419.98: Global MASTER-Net observations report
  75. GRB 210419A: Swift-XRT refined Analysis
  76. GRB 210419C: Swift detection of a burst
  77. Fermi GRB 210419B: Global MASTER-Net observations report
  78. Swift GRB 210419A: Global MASTER-Net observations report
  79. GRB 210419B: Fermi GBM Final Real-time Localization
  80. GRB 210419A: Enhanced Swift-XRT position
  81. GRB 210419A: LCO Optical Upper Limit
  82. GRB 210419A: Swift detection of a burst
  83. GRB 210413B: Swift-XRT observations
  84. Fermi GBM trigger 640353092/210417494 is not a GRB
  85. GRB 210413B: LOAO optical upper limit
  86. Fermi Gamma-ray Burst Monitor trigger 640303939/210416925 is not a GRB
  87. GRB 210411C: A very significant early X-ray afterglow
  88. IceCube Alert 210416.09: Global MASTER-Net observations report
  89. GRB 210413B: Swift ToO observations
  90. IceCubeCascade-210416a: Kanata Optical Imaging of 3C 279
  91. GRB 210413B: Swift/BAT detection and probable localization of a short burst
  92. GRB 210411B: AstroSat CZTI detection
  93. GRB 210410A: AstroSat CZTI detection
  94. GRB 210410A: A twin of short GRB 090510 with complementary observations
  95. Fermi GRB 210415A: Global MASTER-Net observations report
  96. GRB 210415A: Fermi GBM Final Real-time Localization
  97. GRB 210413A: GECAM detection
  98. GRB 210410A: Swift/UVOT Upper Limits (revision)
  99. GRB 210411C: Swift/UVOT Detection
  100. GRB 210411C: Swift-BAT refined analysis

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