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"
  1. GRB 260109A: Fermi GBM Final Real-time Localization
  2. GRB 260104A: Swift-BAT refined analysis
  3. GRB 260101A: Swift-BAT refined analysis
  4. Swift GRB 251230A: Global MASTER-Net OT detection
  5. Fermi GRB 260107A: Global MASTER-Net observations report
  6. GRB 260102A: AbAO optical observations
  7. GRB 260107A: Fermi GBM Final Real-time Localization
  8. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  9. The EP-WXT trigger 01709251112 is likely a flaring star
  10. Fermi GRB 260105A: Global MASTER-Net observations report
  11. GRB 260105B: Fermi GBM Detection
  12. EP260105a: FTW optical observations
  13. EP260104a: FTW optical observations
  14. GRB 260105B: BALROG localization (Fermi Trigger 789348101 / GRB 260105973)
  15. GRB 260105A: SVOM/GRM observation
  16. GRB 260105B: SVOM/GRM observation
  17. The EP-WXT trigger 01709251028 is likely a flaring star
  18. FRB 20251229A: COLIBRÍ optical upper limits
  19. Fermi GRB 260105B: Global MASTER-Net observations report
  20. EP260105a: SVOM/VT optical upperlimit
  21. GRB 260105B: Fermi GBM Final Real-time Localization
  22. GRB 260105A: Fermi GBM Final Real-time Localization
  23. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  24. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  25. EP260105a: LCO Optical Upper limit
  26. EP260104a: Global MASTER-Net observations report
  27. EP260104a: Einstein Probe detection of a fast X-ray transient
  28. GRB 260101A: COLIBRÍ optical upper limits
  29. EP260105a: Global MASTER-Net observations report
  30. EP260105a: Einstein Probe detection of an X-ray transient
  31. GRB 260103A: Insight-HXMT/HE detection
  32. GRB 260104A: COLIBRÍ optical upper limits
  33. GRB 260104C: Fermi GBM Final Real-time Localization
  34. Fermi GRB 260104B: Global MASTER-Net observations report
  35. Swift GRB 260104A: Global MASTER-Net observations report
  36. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  37. GRB 260104A: Swift-XRT refined Analysis
  38. GRB 260104A: Enhanced Swift-XRT position
  39. GRB 260101A: Swift/UVOT Detection
  40. GRB 260103A: GECAM-B observation of a burst
  41. GRB 260104B: Fermi GBM Final Localization
  42. GRB 260104A: Swift detection of a burst
  43. GRB 260103A: SVOM/GRM observation of a possible GRB
  44. Fermi-LAT Gamma-ray Observations of IceCube-251225A
  45. GRB 260101A: COLIBRÍ optical observations
  46. SVOM GRB260103.08: Global MASTER-Net observations report
  47. GRB 260102B: Fermi GBM Final Real-time Localization
  48. SVOM GRB260102A: Global MASTER-Net observations report
  49. Fermi GBM Sub-Threshold Detection of GRB 260102A
  50. GRB 260102A: EP-FXT follow-up observation
  51. EP260101a: Global MASTER-Net observations report
  52. GRB 260102A: LCO optical upper limits
  53. GRB 260102A: Swift-XRT observations
  54. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  55. Fermi Gamma-ray Burst Monitor trigger 789047602/260102495 is not a GRB
  56. GRB 251230A / EP251230a: GECAM-B detection
  57. GRB 260102A: SVOM/VT optical counterpart
  58. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  59. GRB 260102A: Swift ToO observations
  60. GRB 260101A: Fermi GBM Observation
  61. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  62. GRB 260102A: SVOM detection of a burst
  63. GRB 260101A: GECAM-B detection
  64. GRB 260101A: NOT spectroscopic observations
  65. GRB 260101A: SVOM/GRM observation
  66. GRB 260101A: Swift-XRT refined Analysis
  67. Swift GRB 260101A: Global MASTER-Net observations report
  68. GRB 260101A: Enhanced Swift-XRT position
  69. EP260101a: Einstein Probe detection of an X-ray transient
  70. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  71. GRB 260101A: LCO detection of the optical counterpart
  72. GRB 260101A: Swift detection of a burst with an optical counterpart
  73. GRB 260101A: Fermi GBM Final Real-time Localization
  74. SVOM GRB251231.57: Global MASTER-Net observations report
  75. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  76. GRB 251230A: GRANDMA/TAROT Early Detection
  77. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  78. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  79. EP251229a: Optical upper limit with Kinder observations
  80. GRB 251230A: 1.3m DFOT optical upper limit
  81. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  82. GRB 251230A: Swift-XRT refined Analysis
  83. GRB 251231A: Fermi GBM Final Real-time Localization
  84. GRB 251222A: Mondy Optical Observations
  85. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  86. GRB 251230A: Swift/UVOT detection
  87. GRB251230A: 7DT optical upper limits
  88. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  89. EP251229a: BOOTES-2 early optical upper limit
  90. GRB 251230A: GOTO optical upper limit
  91. EP251229a: NOT optical upper limits
  92. GRB 251230A / EP251230a: SVOM/VT optical observation
  93. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  94. GRB 251230A: Enhanced Swift-XRT position
  95. GRB 251230A: Early optical counterpart detection by LCO.
  96. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  97. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  98. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  99. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  100. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory

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