Skip to main content
New! CHIME and DSA-110 FRB Notices, IceCube Notices and Schema v6.1.1. 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. EP260101a: Einstein Probe detection of an X-ray transient
  2. GRB 260101A: OSIRIS+ redshift z = 2.623 for the new year burst
  3. GRB 260101A: LCO detection of the optical counterpart
  4. GRB 260101A: Swift detection of a burst with an optical counterpart
  5. GRB 260101A: Fermi GBM Final Real-time Localization
  6. SVOM GRB251231.57: Global MASTER-Net observations report
  7. GRB 251230A / EP251230a: SVOM/VT optical continued observations and upper limit
  8. GRB 251230A: GRANDMA/TAROT Early Detection
  9. GRB 251230A / EP251230a: further NOT optical observations revealing shallower decay or possible rebrightening
  10. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  11. EP251229a: Optical upper limit with Kinder observations
  12. GRB 251230A: 1.3m DFOT optical upper limit
  13. Fermi Gamma-ray Burst Monitor trigger 788833547/251231018 is not a GRB
  14. GRB 251230A: Swift-XRT refined Analysis
  15. GRB 251231A: Fermi GBM Final Real-time Localization
  16. GRB 251222A: Mondy Optical Observations
  17. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  18. GRB 251230A: Swift/UVOT detection
  19. GRB251230A: 7DT optical upper limits
  20. GRB 251230A / EP251230a: NOT observations and spectroscopic redshift upper limit z < 2.2
  21. EP251229a: BOOTES-2 early optical upper limit
  22. GRB 251230A: GOTO optical upper limit
  23. EP251229a: NOT optical upper limits
  24. GRB 251230A / EP251230a: SVOM/VT optical observation
  25. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  26. GRB 251230A: Enhanced Swift-XRT position
  27. GRB 251230A: Early optical counterpart detection by LCO.
  28. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  29. GRB 251230A: Optical Observations via Virtual Telescope Project, Italy
  30. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  31. GRB 251230A/EP#01709250693 (likely EP251230a): FTW optical and NIR observations
  32. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  33. Swift GRB 251230A: Global MASTER-Net observations report
  34. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  35. EP251229a: Global MASTER-Net observations report
  36. EP251229a: Einstein Probe detection of an X-ray transient
  37. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  38. GRB 251226A: Glowbug gamma-ray detection
  39. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  40. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  41. Fermi GRB 251228A: Global MASTER-Net observations report
  42. The EP-WXT trigger 01709250662 is likely a flaring star
  43. GRB 251228A: Fermi GBM Final Real-time Localization
  44. GRB 251226A: SVOM/GRM observation
  45. GRB 251226A: GECAM-B detection
  46. SVOM GRB251227.07: Global MASTER-Net observations report
  47. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  48. The EP-WXT trigger 01709250617 is likely a flaring star
  49. IceCube Alert 251225.84: Global MASTER-Net observations report
  50. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  51. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  52. GRB 251222A: NUTTelA-TAO Early Measurements
  53. GRB 251222A/EP251222b: Optical detection with Kinder observations
  54. EP251222a: Optical upper limit with Kinder observations
  55. GRB 251221A: Swift-BAT refined analysis
  56. GRB 251222A/EP251222b: FTW optical and NIR observations
  57. EP251222a: FTW optical and NIR observations
  58. GRB 251205A: Kilonova-Catcher optical afterglow detection
  59. GRB 251222A: AbAO optical observations
  60. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  61. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  62. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  63. GRB 251222A: ZTSH BVRI optical observations
  64. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  65. GRB 251222A: Continued 1.3m DFOT optical observation
  66. EP251220a: 3.6m DOT optical afterglow detection
  67. GRB 251222A: Fermi GBM Observation
  68. EP251220a: CrAO ZTSh optical observations
  69. EP251221a: PRIME upper limit
  70. EP251222a: Global MASTER-Net observations report
  71. GRB 251222A / EP251222b: GECAM-B observation
  72. EP251221a: Liverpool Telescope upper limits
  73. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  74. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  75. Konus-Wind detection of GRB 251222A / EP251222b
  76. GRB 251222A: Swift-XRT afterglow detection
  77. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  78. EP251222a: NTT/ULTRACAM optical observations
  79. EP251222a: GOTO optical upper limit
  80. GRB 251222A / EP251222b: GOTO optical counterpart detection
  81. GRB 251222A / EP251222b: LCO optical observations
  82. GRB 251222A: 1.3m DFOT optical detection
  83. GRB251221A: 7DT optical upper limits
  84. EP251222a: GSP Optical Counterpart Detection
  85. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  86. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  87. EP251222b/GRB 251222A: SVOM/GRM observation
  88. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  89. EP251222a: Einstein Probe detection of an X-ray transient
  90. The EP-WXT trigger 01709250397 is likely a flaring star
  91. EP251221a: Global MASTER-Net observations report
  92. GRB 251222A: PRIME near-infrared detection
  93. EP251221a: NOT optical upper limit
  94. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  95. GRB 251222A: NOT optical observations
  96. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  97. IPN triangulation of GRB 251220B (short)
  98. GRB 251222A: Swift ToO observations
  99. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  100. GRB 251222A: SVOM/VT optical candidate

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