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. GRB 251230A / EP251230a: GECAM-B detection
  2. GRB 260102A: SVOM/VT optical counterpart
  3. GRB 251230A / EP251230a: Insight-HXMT/HE detection
  4. GRB 260102A: Swift ToO observations
  5. GRB 260101A: Fermi GBM Observation
  6. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  7. GRB 260102A: SVOM detection of a burst
  8. GRB 260101A: GECAM-B detection
  9. GRB 260101A: NOT spectroscopic observations
  10. GRB 260101A: SVOM/GRM observation
  11. GRB 260101A: Swift-XRT refined Analysis
  12. Swift GRB 260101A: Global MASTER-Net observations report
  13. GRB 260101A: Enhanced Swift-XRT position
  14. EP260101a: Einstein Probe detection of an X-ray transient
  15. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  16. GRB 260101A: LCO detection of the optical counterpart
  17. GRB 260101A: Swift detection of a burst with an optical counterpart
  18. GRB 260101A: Fermi GBM Final Real-time Localization
  19. SVOM GRB251231.57: Global MASTER-Net observations report
  20. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  21. GRB 251230A: GRANDMA/TAROT Early Detection
  22. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  23. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  24. EP251229a: Optical upper limit with Kinder observations
  25. GRB 251230A: 1.3m DFOT optical upper limit
  26. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  27. GRB 251230A: Swift-XRT refined Analysis
  28. GRB 251231A: Fermi GBM Final Real-time Localization
  29. GRB 251222A: Mondy Optical Observations
  30. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  31. GRB 251230A: Swift/UVOT detection
  32. GRB251230A: 7DT optical upper limits
  33. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  34. EP251229a: BOOTES-2 early optical upper limit
  35. GRB 251230A: GOTO optical upper limit
  36. EP251229a: NOT optical upper limits
  37. GRB 251230A / EP251230a: SVOM/VT optical observation
  38. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  39. GRB 251230A: Enhanced Swift-XRT position
  40. GRB 251230A: Early optical counterpart detection by LCO.
  41. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  42. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  43. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  44. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  45. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  46. Swift GRB 251230A: Global MASTER-Net observations report
  47. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  48. EP251229a: Global MASTER-Net observations report
  49. EP251229a: Einstein Probe detection of an X-ray transient
  50. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  51. GRB 251226A: Glowbug gamma-ray detection
  52. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  53. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  54. Fermi GRB 251228A: Global MASTER-Net observations report
  55. The EP-WXT trigger 01709250662 is likely a flaring star
  56. GRB 251228A: Fermi GBM Final Real-time Localization
  57. GRB 251226A: SVOM/GRM observation
  58. GRB 251226A: GECAM-B detection
  59. SVOM GRB251227.07: Global MASTER-Net observations report
  60. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  61. The EP-WXT trigger 01709250617 is likely a flaring star
  62. IceCube Alert 251225.84: Global MASTER-Net observations report
  63. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  64. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  65. GRB 251222A: NUTTelA-TAO Early Measurements
  66. GRB 251222A/EP251222b: Optical detection with Kinder observations
  67. EP251222a: Optical upper limit with Kinder observations
  68. GRB 251221A: Swift-BAT refined analysis
  69. GRB 251222A/EP251222b: FTW optical and NIR observations
  70. EP251222a: FTW optical and NIR observations
  71. GRB 251205A: Kilonova-Catcher optical afterglow detection
  72. GRB 251222A: AbAO optical observations
  73. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  74. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  75. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  76. GRB 251222A: ZTSH BVRI optical observations
  77. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  78. GRB 251222A: Continued 1.3m DFOT optical observation
  79. EP251220a: 3.6m DOT optical afterglow detection
  80. GRB 251222A: Fermi GBM Observation
  81. EP251220a: CrAO ZTSh optical observations
  82. EP251221a: PRIME upper limit
  83. EP251222a: Global MASTER-Net observations report
  84. GRB 251222A / EP251222b: GECAM-B observation
  85. EP251221a: Liverpool Telescope upper limits
  86. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  87. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  88. Konus-Wind detection of GRB 251222A / EP251222b
  89. GRB 251222A: Swift-XRT afterglow detection
  90. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  91. EP251222a: NTT/ULTRACAM optical observations
  92. EP251222a: GOTO optical upper limit
  93. GRB 251222A / EP251222b: GOTO optical counterpart detection
  94. GRB 251222A / EP251222b: LCO optical observations
  95. GRB 251222A: 1.3m DFOT optical detection
  96. GRB251221A: 7DT optical upper limits
  97. EP251222a: GSP Optical Counterpart Detection
  98. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  99. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  100. EP251222b/GRB 251222A: SVOM/GRM observation

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