Skip to main content
New! BOOM Notices and Schema v7.0.0. 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. EP260105a: FTW optical observations
  2. EP260104a: FTW optical observations
  3. GRB 260105B: BALROG localization (Fermi Trigger 789348101 / GRB 260105973)
  4. GRB 260105A: SVOM/GRM observation
  5. GRB 260105B: SVOM/GRM observation
  6. The EP-WXT trigger 01709251028 is likely a flaring star
  7. FRB 20251229A: COLIBRÍ optical upper limits
  8. Fermi GRB 260105B: Global MASTER-Net observations report
  9. EP260105a: SVOM/VT optical upperlimit
  10. GRB 260105B: Fermi GBM Final Real-time Localization
  11. GRB 260105A: Fermi GBM Final Real-time Localization
  12. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  13. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  14. EP260105a: LCO Optical Upper limit
  15. EP260104a: Global MASTER-Net observations report
  16. EP260104a: Einstein Probe detection of a fast X-ray transient
  17. GRB 260101A: COLIBRÍ optical upper limits
  18. EP260105a: Global MASTER-Net observations report
  19. EP260105a: Einstein Probe detection of an X-ray transient
  20. GRB 260103A: Insight-HXMT/HE detection
  21. GRB 260104A: COLIBRÍ optical upper limits
  22. GRB 260104C: Fermi GBM Final Real-time Localization
  23. Fermi GRB 260104B: Global MASTER-Net observations report
  24. Swift GRB 260104A: Global MASTER-Net observations report
  25. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  26. GRB 260104A: Swift-XRT refined Analysis
  27. GRB 260104A: Enhanced Swift-XRT position
  28. GRB 260101A: Swift/UVOT Detection
  29. GRB 260103A: GECAM-B observation of a burst
  30. GRB 260104B: Fermi GBM Final Localization
  31. GRB 260104A: Swift detection of a burst
  32. GRB 260103A: SVOM/GRM observation of a possible GRB
  33. Fermi-LAT Gamma-ray Observations of IceCube-251225A
  34. GRB 260101A: COLIBRÍ optical observations
  35. SVOM GRB260103.08: Global MASTER-Net observations report
  36. GRB 260102B: Fermi GBM Final Real-time Localization
  37. SVOM GRB260102A: Global MASTER-Net observations report
  38. Fermi GBM Sub-Threshold Detection of GRB 260102A
  39. GRB 260102A: EP-FXT follow-up observation
  40. EP260101a: Global MASTER-Net observations report
  41. GRB 260102A: LCO optical upper limits
  42. GRB 260102A: Swift-XRT observations
  43. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  44. Fermi Gamma-ray Burst Monitor trigger 789047602/260102495 is not a GRB
  45. GRB 251230A / EP251230a: GECAM-B detection
  46. GRB 260102A: SVOM/VT optical counterpart
  47. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  48. GRB 260102A: Swift ToO observations
  49. GRB 260101A: Fermi GBM Observation
  50. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  51. GRB 260102A: SVOM detection of a burst
  52. GRB 260101A: GECAM-B detection
  53. GRB 260101A: NOT spectroscopic observations
  54. GRB 260101A: SVOM/GRM observation
  55. GRB 260101A: Swift-XRT refined Analysis
  56. Swift GRB 260101A: Global MASTER-Net observations report
  57. GRB 260101A: Enhanced Swift-XRT position
  58. EP260101a: Einstein Probe detection of an X-ray transient
  59. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  60. GRB 260101A: LCO detection of the optical counterpart
  61. GRB 260101A: Swift detection of a burst with an optical counterpart
  62. GRB 260101A: Fermi GBM Final Real-time Localization
  63. SVOM GRB251231.57: Global MASTER-Net observations report
  64. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  65. GRB 251230A: GRANDMA/TAROT Early Detection
  66. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  67. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  68. EP251229a: Optical upper limit with Kinder observations
  69. GRB 251230A: 1.3m DFOT optical upper limit
  70. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  71. GRB 251230A: Swift-XRT refined Analysis
  72. GRB 251231A: Fermi GBM Final Real-time Localization
  73. GRB 251222A: Mondy Optical Observations
  74. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  75. GRB 251230A: Swift/UVOT detection
  76. GRB251230A: 7DT optical upper limits
  77. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  78. EP251229a: BOOTES-2 early optical upper limit
  79. GRB 251230A: GOTO optical upper limit
  80. EP251229a: NOT optical upper limits
  81. GRB 251230A / EP251230a: SVOM/VT optical observation
  82. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  83. GRB 251230A: Enhanced Swift-XRT position
  84. GRB 251230A: Early optical counterpart detection by LCO.
  85. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  86. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  87. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  88. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  89. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  90. Swift GRB 251230A: Global MASTER-Net observations report
  91. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  92. EP251229a: Global MASTER-Net observations report
  93. EP251229a: Einstein Probe detection of an X-ray transient
  94. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  95. GRB 251226A: Glowbug gamma-ray detection
  96. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  97. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  98. Fermi GRB 251228A: Global MASTER-Net observations report
  99. The EP-WXT trigger 01709250662 is likely a flaring star
  100. GRB 251228A: Fermi GBM Final Real-time Localization

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