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"
  1. Fermi GRB 211023A: Global MASTER-Net observations report
  2. GRB 211023A: AGILE detection
  3. GRB 211022A: AstroSat CZTI detection
  4. GRB 211023B: Swift-XRT refined Analysis
  5. GRB 211023B: Enhanced Swift-XRT position
  6. GRB 211023A: Fermi GBM detection
  7. Swift GRB 211023B: Global MASTER-Net observations report
  8. Fermi GRB 211024A: Global MASTER-Net observations report
  9. GRB 211024A: Fermi GBM Final Real-time Localization
  10. GRB 211023A: Fermi-LAT detection
  11. GRB 211023B: Swift detection of a possibly short burst with an optical counterpart
  12. IceCube Alert 211023.36: Global MASTER-Net observations report
  13. GRB 211023A: Fermi GBM Final Real-time Localization
  14. IceCube-211023A - IceCube observation of a high-energy neutrino candidate track-like event
  15. IPN Triangulation of GRB 210927B
  16. GRB 211022A: GECAM detection
  17. AMON IC_HAWC NuEm-211020A: No neutrino counterpart detected with ANTARES
  18. GRB 211018A: Swift ToO observations
  19. GRB 211021A: BALROG localization (Fermi Trigger 656506979 / GRB 211021460)
  20. Fermi trigger No 656506979: Global MASTER-Net observations report
  21. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-211020A
  22. BepiColombo MGNS joins the IPN
  23. Fermi trigger No 656268212: Global MASTER-Net observations report
  24. GRB 211018A: Fermi GBM observation
  25. GRB 211019A: Detection by GRBAlpha
  26. GRB 211018A: Detection by GRBAlpha
  27. Fermi GRB 211019A: Global MASTER-Net observations report
  28. GRB 211018A: Fermi-LAT detection
  29. GRB 211019A: BALROG localization (Fermi Trigger 656315976 / GRB 211019250)
  30. GRB 211019A: Fermi GBM Final Real-time Localization
  31. Fermi trigger No 656288898: Global MASTER-Net observations report
  32. Swift GRB211017.99: Global MASTER-Net observations report
  33. Integral GRB211016.42: Global MASTER-Net observations report
  34. IceCube-210922A: Hard X-ray flux limit for JCMT/SCUBA2 source from NuSTAR observations
  35. Swift trigger 1078701: MITSuME Akeno optical upper limits
  36. Fermi trigger No 655673024: Global MASTER-Net observations report
  37. GRB 210919A: LDT optical observations and candidate host galaxies
  38. IceCube-20210922A: No optical counterparts found by MITSuME observations
  39. Swift Trigger 1078701: Mondy, CrAO, AbAO observations, possible optical counterpart
  40. Fermi trigger No 655646385: Global MASTER-Net observations report
  41. Swift GRB211010.45: Global MASTER-Net observations report
  42. Swift Trigger 1078701 is probably not a GRB
  43. Fermi Gamma-ray Burst Monitor trigger 211008665/655401471 is not a GRB
  44. IceCube-20210922A: DESNU Optical counterpart candidate from 5 nights of DECam observations
  45. GRB 211008A: BALROG localization (Fermi Trigger 655401471 / GRB 211008665)
  46. Fermi trigger No 655401471: Global MASTER-Net observations report
  47. GRB 210928A: MeerKAT detection
  48. IceCube-210922A: DESI Observations
  49. GECAM observation of a burst from SGR J1555.2-5402
  50. Konus-Wind detection of GRB 210928A
  51. Fermi trigger No 654854799: Global MASTER-Net observations report
  52. Correction to GCN 30915: GRB 210928A: Swift-XRT analysis
  53. GRB 210928A: Kinder SLT-40cm optical limits
  54. GRB 210930A: Swift-BAT refined analysis
  55. SGR 1935+2154: Swift/BAT-GUANO detection and arcminute localization
  56. GRB 210928A: Swift-XRT analysis (replaces GCN 30914)
  57. GRB 210928A: Swift-XRT refined Analysis
  58. GRB 210928A: Fermi GBM observation
  59. GRB 210928A: Fermi-LAT detection
  60. Swift GRB211001.03 / trigger 1076121 : MASTER OT retraction
  61. GRB 210927B: GECAM detection
  62. GRB 210930A: CAHA 2.2m telescope optical limit
  63. GRB 210927A: GIT optical follow-up of ZTF21acdwctm.
  64. Fermi trigger No 654739449: Global MASTER-Net observations report
  65. Swift GRB211001.03: Global MASTER-Net observations report
  66. Swift Trigger 1076121 is not a GRB
  67. Swift GRB211001.03: Global MASTER-Net OT detection
  68. GRB 210930A: Swift/UVOT Upper Limits
  69. GRB 210930A: Swift-XRT refined Analysis
  70. Swift GRB 210930A: Global MASTER-Net observations report
  71. GRB 210930A: Enhanced Swift-XRT position
  72. Fermi trigger No 654658271: Global MASTER-Net observations report
  73. Fermi GRB 210929B: Global MASTER-Net observations report
  74. GRB 210930A: Swift detection of a burst
  75. GRB 210929B: Fermi GBM Final Real-time Localization
  76. Fermi-LAT Gamma-ray Observations of IceCubeCascade-210926A
  77. GRB 210929A: Fermi GBM Final Real-time Localization
  78. GRB 210927A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 654396242)
  79. GRB 210925B: AstroSat CZTI detection
  80. IceCube-210922A: SMA observation for the JCMT candidate
  81. IPN triangulation of GRB 210925B
  82. GRB 210926A: AstroSat CZTI detection
  83. GRB 210919A: iTelescope T-11 upper limits
  84. IceCube-210926A: No neutrino counterpart candidates in ANTARES search
  85. GRB 210926A: GECAM detection
  86. GRB 210927A: Fermi GBM Final Real-time Localization
  87. GRB 210919A OSN 1.5m Source Confirmation
  88. GRB 210919A CAHA 2.2m Observations: Afterglow/Host Galaxy Candidate
  89. IceCube-210922A: JCMT/SCUBA2 observations
  90. GRB 210925A: GECAM detection
  91. GRB 210925A: Fermi GBM Final Real-time Localization
  92. GRB 210919A: Chandra rapid ToO upper limit
  93. GRB 210924A: Fermi GBM Final Real-time Localization
  94. IceCube-210922A: No Candidate Counterparts from Swift/XRT follow up observations
  95. IceCube-210922A: No significant detection in HAWC
  96. IceCube-210922A: No neutrino counterpart candidates in ANTARES search
  97. GRB 210923B: GECAM detection
  98. Retraction of Fermi GBM GRB 210923A: the trigger is not a GRB
  99. IceCube-210922A: Upper limits from a search for additional neutrino events in IceCube
  100. IceCube-210922A: Upper limits from Fermi-GBM Observations

Advanced

Download all Circulars as a .tar.gz archive:
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