Skip to main content
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. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  2. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  3. EP260105a: LCO Optical Upper limit
  4. EP260104a: Global MASTER-Net observations report
  5. EP260104a: Einstein Probe detection of a fast X-ray transient
  6. GRB 260101A: COLIBRÍ optical upper limits
  7. EP260105a: Global MASTER-Net observations report
  8. EP260105a: Einstein Probe detection of an X-ray transient
  9. GRB 260103A: Insight-HXMT/HE detection
  10. GRB 260104A: COLIBRÍ optical upper limits
  11. GRB 260104C: Fermi GBM Final Real-time Localization
  12. Fermi GRB 260104B: Global MASTER-Net observations report
  13. Swift GRB 260104A: Global MASTER-Net observations report
  14. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  15. GRB 260104A: Swift-XRT refined Analysis
  16. GRB 260104A: Enhanced Swift-XRT position
  17. GRB 260101A: Swift/UVOT Detection
  18. GRB 260103A: GECAM-B observation of a burst
  19. GRB 260104B: Fermi GBM Final Localization
  20. GRB 260104A: Swift detection of a burst
  21. GRB 260103A: SVOM/GRM observation of a possible GRB
  22. Fermi-LAT Gamma-ray Observations of IceCube-251225A
  23. GRB 260101A: COLIBRÍ optical observations
  24. SVOM GRB260103.08: Global MASTER-Net observations report
  25. GRB 260102B: Fermi GBM Final Real-time Localization
  26. SVOM GRB260102A: Global MASTER-Net observations report
  27. Fermi GBM Sub-Threshold Detection of GRB 260102A
  28. GRB 260102A: EP-FXT follow-up observation
  29. EP260101a: Global MASTER-Net observations report
  30. GRB 260102A: LCO optical upper limits
  31. GRB 260102A: Swift-XRT observations
  32. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  33. Fermi Gamma-ray Burst Monitor trigger 789047602/260102495 is not a GRB
  34. GRB 251230A / EP251230a: GECAM-B detection
  35. GRB 260102A: SVOM/VT optical counterpart
  36. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  37. GRB 260102A: Swift ToO observations
  38. GRB 260101A: Fermi GBM Observation
  39. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  40. GRB 260102A: SVOM detection of a burst
  41. GRB 260101A: GECAM-B detection
  42. GRB 260101A: NOT spectroscopic observations
  43. GRB 260101A: SVOM/GRM observation
  44. GRB 260101A: Swift-XRT refined Analysis
  45. Swift GRB 260101A: Global MASTER-Net observations report
  46. GRB 260101A: Enhanced Swift-XRT position
  47. EP260101a: Einstein Probe detection of an X-ray transient
  48. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  49. GRB 260101A: LCO detection of the optical counterpart
  50. GRB 260101A: Swift detection of a burst with an optical counterpart
  51. GRB 260101A: Fermi GBM Final Real-time Localization
  52. SVOM GRB251231.57: Global MASTER-Net observations report
  53. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  54. GRB 251230A: GRANDMA/TAROT Early Detection
  55. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  56. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  57. EP251229a: Optical upper limit with Kinder observations
  58. GRB 251230A: 1.3m DFOT optical upper limit
  59. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  60. GRB 251230A: Swift-XRT refined Analysis
  61. GRB 251231A: Fermi GBM Final Real-time Localization
  62. GRB 251222A: Mondy Optical Observations
  63. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  64. GRB 251230A: Swift/UVOT detection
  65. GRB251230A: 7DT optical upper limits
  66. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  67. EP251229a: BOOTES-2 early optical upper limit
  68. GRB 251230A: GOTO optical upper limit
  69. EP251229a: NOT optical upper limits
  70. GRB 251230A / EP251230a: SVOM/VT optical observation
  71. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  72. GRB 251230A: Enhanced Swift-XRT position
  73. GRB 251230A: Early optical counterpart detection by LCO.
  74. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  75. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  76. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  77. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  78. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  79. Swift GRB 251230A: Global MASTER-Net observations report
  80. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  81. EP251229a: Global MASTER-Net observations report
  82. EP251229a: Einstein Probe detection of an X-ray transient
  83. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  84. GRB 251226A: Glowbug gamma-ray detection
  85. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  86. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  87. Fermi GRB 251228A: Global MASTER-Net observations report
  88. The EP-WXT trigger 01709250662 is likely a flaring star
  89. GRB 251228A: Fermi GBM Final Real-time Localization
  90. GRB 251226A: SVOM/GRM observation
  91. GRB 251226A: GECAM-B detection
  92. SVOM GRB251227.07: Global MASTER-Net observations report
  93. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  94. The EP-WXT trigger 01709250617 is likely a flaring star
  95. IceCube Alert 251225.84: Global MASTER-Net observations report
  96. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  97. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  98. GRB 251222A: NUTTelA-TAO Early Measurements
  99. GRB 251222A/EP251222b: Optical detection with Kinder observations
  100. EP251222a: Optical upper limit with Kinder 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