Skip to main content
Due to the lapse in federal government funding, NASA is not updating this website. See the Operations FAQ for GCN impacts.
New! Super-Kamiokande JSON Notices and Schema v4.5.0. 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. 230211A is not a GRB
  2. GRB 230211A: Fermi GBM Final Real-time Localization
  3. GRB 230209B: Swift/BAT-GUANO detection outside the coded FOV
  4. Fermi trigger No 697678542: Global MASTER-Net observations report
  5. Swift Trigger 1153670 is probably not a GRB
  6. GRB 230210A: Fermi GBM Final Real-time Localization
  7. Fermi GRB 230209B: Global MASTER-Net observations report
  8. GRB 230209B: Fermi GBM Final Real-time Localization
  9. GRB 230205A: 6 GHz VLA observations
  10. GRB 230209A is not a GRB
  11. GRB 230205A: SUBARU HSC pre-imaging for host galaxy search
  12. GRB 230209A: Fermi GBM Final Real-time Localization
  13. GRB 221009A: Continued Swift Observations
  14. Fermi Gamma-ray Burst Monitor trigger 230208382/697540213 is not a GRB
  15. GRB 230207B: Detection by GRBAlpha
  16. GRB 230205A: possible host galaxy detection with the Schmidt - Asiago telescope
  17. GRB 230204B: MASTER early OT detection
  18. GRB 230208A: Fermi GBM Final Real-time Localization
  19. Fermi Gamma-ray Burst Monitor triggers 230206723/697396830 and 230206797/697403223 are not GRBs
  20. GRB 230207B: Swift/BAT-GUANO detection outside the coded FOV
  21. ZTF23aabmzlp/AT2023azs: Neil Gehrels Swift Observatory X-ray observations
  22. GRB 230207B: AGILE detection of a burst
  23. Fermi GRB 230207A: Global MASTER-Net observations report
  24. GRB 230207A: Fermi GBM Final Real-time Localization
  25. GRB 230204B: LCOGT Optical Upper Limits
  26. GRB 230204B: Swift/UVOT Upper Limits
  27. Fermi trigger No 697403223: Global MASTER-Net observations report
  28. Fermi trigger No 697396830: Global MASTER-Net observations report
  29. GRB 230205A: Swift/UVOT Upper Limits
  30. GRB 230204B: Fermi GBM detection
  31. Fermi Gamma-ray Burst Monitor triggers due to recent activity of RX J0440.9+4431 (LS V +44 17)
  32. GRB 230205A: LCOGT Optical Upper Limits
  33. GRB 230204B: Swift-XRT afterglow detection
  34. GRB 230204B: 3.6m DOT optical observation
  35. GRB 230205A: SVOM/C-GFT optical upper limit
  36. GRB 230205A: OHP/T193 optical observations
  37. GRB 230204B: VLT/X-shooter redshift
  38. GRB 230205A: Swift-BAT refined analysis (T90 = 2.3 s)
  39. GRB 230204A: Swift-BAT refined analysis
  40. GRB 230204B: ATLAS detection of the optical afterglow and a projected location in a nearby galaxy group
  41. GRB 230205A: Swift-XRT refined Analysis
  42. GRB 230204B: Swift ToO observations
  43. GRB 230205A: Enhanced Swift-XRT position
  44. GRB 230205A: BOOTES-5/JGT early optical upper limit
  45. GRB 230204B: Detection by GRBAlpha
  46. GRB 230204B: AGILE detection
  47. GRB 230205A: Swift detection of a burst
  48. IceCube-230201A: BOOTES-4/MET Optical Upper Limits
  49. GRB 230204B: GIT discovery of the likely optical afterglow
  50. GRB 230204B: AstroSat CZTI detection
  51. GRB 230204B: Swift/BAT-GUANO detection outside the coded FOV
  52. GRB 230204A: Swift/UVOT Upper Limits
  53. GRB 230204B: MAXI/GSC detection
  54. GRB 230204A: Swift-XRT refined Analysis
  55. GRB 230204A/Swift J1552.8-5055: LCOGT Optical Counterpart Candidate
  56. Fermi trigger No 697208885: Global MASTER-Net observations report
  57. GRB 230204A: Enhanced Swift-XRT position
  58. GRB 230204A: Swift detection of a possible burst (or possible transient Swift J1552.8-5055)
  59. GRB 230201B: TURBO Optical Upper Limits
  60. Fermi Gamma-ray Burst Monitor trigger 230203275 / 697098930 is not a GRB
  61. Fermi trigger No 697098930: Global MASTER-Net observations report
  62. IceCube-230201A: Upper limits from a search for additional neutrino events in IceCube
  63. ZTF23aabmzlp/AT2023azs: Lulin 1m LOT optical observations
  64. GRB 221216A: Swift-BAT refined analysis
  65. ZTF23aabmzlp/AT2023azs: VLA radio detection
  66. ZTF23aaarlti/AT2023avj: AMI-LA radio detection
  67. ZTF23aabmzlp/AT2023azs: AMI-LA radio upper limit
  68. IceCube Alert 230201.26: Global MASTER-Net observations report
  69. Fermi GRB 230201B: Global MASTER-Net observations report
  70. Fermi-LAT gamma-ray observations of IceCube-230201A
  71. GRB 230201B: Fermi GBM Final Real-time Localization
  72. GRB 230126A: Detection by VZLUSAT-2
  73. Fermi GRB 230201A: Global MASTER-Net observations report
  74. IceCube-230201A - IceCube observation of a high-energy neutrino candidate track-like event
  75. GRB 221009A: radio afterglow detection with the EVN
  76. GRB 230201A: Fermi GBM Final Real-time Localization
  77. ZTF23aabmzlp/AT2023azs: LCOGT Optical Detection
  78. ZTF23aaarlti/AT2023avj: Assy continued optical observations
  79. ZTF23aabmzlp/AT2023azs: Mondy and AbAO optical observations
  80. AT2023avj: X-ray Detection with Swift/XRT
  81. ZTF23aabmzlp/AT2023azs: 1.3m DFOT optical observations
  82. GRB 230129A: AstroSat CZTI detection
  83. GRB 230128A: AstroSat CZTI detection
  84. GRB 230130A: Fermi GBM Final Real-time Localization
  85. ZTF23aaarlti/AT2023avj: VLA radio detection
  86. GRB 230129A: Fermi GBM Final Real-time Localization
  87. GRB 230128A: Fermi GBM Final Real-time Localization
  88. ZTF23aabmzlp/AT2023azs: GIT confirmation of the likely afterglow
  89. ZTF23aabmzlp/AT2023azs: Zwicky Transient Facility discovery of a fast optical transient
  90. IceCube-230122A: BOOTES-2/TELMA Optical Upper Limit
  91. AT2023avj ZTF Candidate: Assy optical observations
  92. ZTF and LT Observations of AT2023avj, a Candidate Optical Afterglow
  93. GRB 230126A: Fermi GBM Final Real-time Localization
  94. Swift-XRT observations of NuEm-230125A
  95. Trigger 1150965: Swift detection of LS V +44 17
  96. GRB 230124A: Fermi GBM Observation
  97. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-230125A
  98. GRB 230124A: Swift/BAT-GUANO detection outside the coded FOV
  99. IceCube-230122A: Upper limits from a search for additional neutrino events in IceCube
  100. GRB 230114B: Detection by VZLUSAT-2

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