Skip to main content
Due to the lapse in federal government funding, NASA is not updating this website. See the Operations FAQ for GCN impacts.
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. SVOM GRB251106.83: Global MASTER-Net observations report
  2. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  3. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  4. IPN triangulation of GRB 251105B (possible sGRB with EE)
  5. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  6. GRB 251106B: SVOM/GRM observation of a short burst
  7. GRB 251106A: Swift-XRT afterglow detection
  8. GRB 251106A: Kilonova-Catcher optical upper limit
  9. Fermi GBM Sub-Threshold Detection of GRB 251106A
  10. GRB 251106A: Swift/BAT arcminute localization of a burst
  11. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  12. GRB 251106A: MASTER optical observations
  13. GRB 251106A: SVOM detection of a burst
  14. GRB 251103B: AstroSat CZTI detection
  15. GRB 251025C: TERI Gamma-ray detection
  16. GRB 251016B: TERI Gamma-ray detection
  17. GRB 251016A: TERI Gamma-ray detection of a short burst
  18. GRB 250920C: TERI Gamma-ray detection
  19. Fermi trigger No 784034269: Global MASTER-Net observations report
  20. Fermi Gamma-ray Burst Monitor trigger 784109140/251106337 is not a GRB
  21. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  22. GRB 251105A: Fermi GBM Observation
  23. GRB 251105C: Fermi GBM Final Localization Correction
  24. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  25. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  26. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  27. GRB 251105B: AstroSat CZTI detection of a short burst with extended emission
  28. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  29. Fermi GBM Sub-Threshold Detection of GRB 251105B
  30. GRB 251103B: Swift/UVOT Upper Limits
  31. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  32. GRB 251105B: SVOM/GRM observation of a possible short burst with extended emission
  33. Fermi GRB 251105A: Global MASTER-Net observations report
  34. GRB 251105A: Fermi GBM Final Real-time Localization
  35. Fermi Gamma-ray Burst Monitor trigger 783986701/251104920 is not a GRB
  36. GRB 251103B: Fermi GBM observation
  37. GRB 251104A: SVOM detection of a burst
  38. GRB 251028A: Insight-HXMT/HE detection
  39. GRB 251103A: Optical afterglow detection by ZTF’s public survey
  40. EP251102a: FTW optical and NIR observations
  41. GRB 251103A: WFST optical observations
  42. EP251102a: update of EP-FXT follow-up observation
  43. EP251102a: OHP/T193 optical observations
  44. GRB 251103A: OHP/T193 optical observations
  45. GRB 251103A: Xinglong 2.16m optical detection
  46. GRB 251103A: Insight-HXMT detection
  47. GRB 251103A: KAIT optical observations
  48. GRB 251103B: Nanshan/HMT optical upper limit
  49. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  50. GRB 251103A: Swift/BAT-GUANO arcminute localization of a burst
  51. GRB 251103B: MITSuME Akeno optical upper limits
  52. GRB 251103B: Swift-XRT refined Analysis
  53. Fermi GRB 251103A: Global MASTER-Net observations report
  54. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  55. EP251102a: NIR observations with WINTER
  56. GRB 251103A: J-band detection with WINTER
  57. Swift GRB 251103B: Global MASTER-Net observations report
  58. GRB 251103B: GROWTH-India Telescope optical upper limits
  59. GRB 251103A: Kilonova-Catcher optical afterglow detection
  60. GRB 251103B: Enhanced Swift-XRT position
  61. GRB 251103B: Prompt enhanced Swift-XRT position
  62. GRB 251103B: Swift detection of a burst
  63. GRB 251103B: Fermi GBM Final Real-time Localization
  64. GRB 251103A: Swift/UVOT Detection
  65. GRB 251103A: Fermi GBM Observation
  66. GRB 251103A: SVOM/GRM observation
  67. GRB 251103A: Swift-XRT afterglow detection
  68. LIGO/Virgo/KAGRA S251031cq: Updated Sky localization
  69. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  70. EP251102a: Einstein Probe detection of a fast X-ray transient
  71. GRB 251025B: OHP/T193 optical upper limit
  72. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  73. GRB 251103A: LCO optical observation
  74. EP251102.890: COLIBRÍ optical counterpart candidate
  75. GRB 251103A: GOTO optical afterglow detection
  76. GRB 251102A: AstroSat CZTI detection
  77. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  78. GRB 251103A: NOT spectroscopic redshift z = 0.76
  79. GRB 251103A: BOOTES-2/TELMA optical afterglow
  80. GRB 251103A: LCO optical afterglow detection
  81. GRB 251103A: NOT optical afterglow candidate (duplicate submission)
  82. GRB 251103A: Fermi GBM Final Localization
  83. GRB 251103A: NOT optical afterglow candidate
  84. GRB 251103A: SVOM detection of a bright burst
  85. GRB 251102B: Fermi GBM Final Real-time Localization
  86. Fermi GRB 251102A: Global MASTER-Net observations report
  87. GRB 251102A: Fermi GBM Final Real-time Localization
  88. GRB 251031A: Fermi GBM Observation
  89. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  90. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  91. Konus-Wind detection of GRB 251028A
  92. GRB 251031A: BALROG localization (Fermi Trigger 783588065 / GRB 251031306)
  93. GRB 251031A: Fermi GBM Final Real-time Localization
  94. GRB 251025C: SVOM/GRM observation
  95. GRB 251028A: GECAM-B detection
  96. GRB 251028A: SVOM/GRM observation
  97. IceCube-251025A: Two Transient Candidates from the Zwicky Transient Facility
  98. GRB 251028A: Fermi GBM Observation
  99. GRB 251026B: SOAR Classification of GOTO25jgl/SN2025absf as a Type Ia supernova
  100. GRB 251022A: Swift-XRT confirmation of fading

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