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. Fermi GBM Sub-Threshold Detection of GRB 251106A
  2. GRB 251106A: Swift/BAT arcminute localization of a burst
  3. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  4. GRB 251106A: MASTER optical observations
  5. GRB 251106A: SVOM detection of a burst
  6. GRB 251103B: AstroSat CZTI detection
  7. GRB 251025C: TERI Gamma-ray detection
  8. GRB 251016B: TERI Gamma-ray detection
  9. GRB 251016A: TERI Gamma-ray detection of a short burst
  10. GRB 250920C: TERI Gamma-ray detection
  11. Fermi trigger No 784034269: Global MASTER-Net observations report
  12. Fermi Gamma-ray Burst Monitor trigger 784109140/251106337 is not a GRB
  13. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  14. GRB 251105A: Fermi GBM Observation
  15. GRB 251105C: Fermi GBM Final Localization Correction
  16. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  17. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  18. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  19. GRB 251105B: AstroSat CZTI detection of a short burst with extended emission
  20. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  21. Fermi GBM Sub-Threshold Detection of GRB 251105B
  22. GRB 251103B: Swift/UVOT Upper Limits
  23. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  24. GRB 251105B: SVOM/GRM observation of a possible short burst with extended emission
  25. Fermi GRB 251105A: Global MASTER-Net observations report
  26. GRB 251105A: Fermi GBM Final Real-time Localization
  27. Fermi Gamma-ray Burst Monitor trigger 783986701/251104920 is not a GRB
  28. GRB 251103B: Fermi GBM observation
  29. GRB 251104A: SVOM detection of a burst
  30. GRB 251028A: Insight-HXMT/HE detection
  31. GRB 251103A: Optical afterglow detection by ZTF’s public survey
  32. EP251102a: FTW optical and NIR observations
  33. GRB 251103A: WFST optical observations
  34. EP251102a: update of EP-FXT follow-up observation
  35. EP251102a: OHP/T193 optical observations
  36. GRB 251103A: OHP/T193 optical observations
  37. GRB 251103A: Xinglong 2.16m optical detection
  38. GRB 251103A: Insight-HXMT detection
  39. GRB 251103A: KAIT optical observations
  40. GRB 251103B: Nanshan/HMT optical upper limit
  41. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  42. GRB 251103A: Swift/BAT-GUANO arcminute localization of a burst
  43. GRB 251103B: MITSuME Akeno optical upper limits
  44. GRB 251103B: Swift-XRT refined Analysis
  45. Fermi GRB 251103A: Global MASTER-Net observations report
  46. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  47. EP251102a: NIR observations with WINTER
  48. GRB 251103A: J-band detection with WINTER
  49. Swift GRB 251103B: Global MASTER-Net observations report
  50. GRB 251103B: GROWTH-India Telescope optical upper limits
  51. GRB 251103A: Kilonova-Catcher optical afterglow detection
  52. GRB 251103B: Enhanced Swift-XRT position
  53. GRB 251103B: Prompt enhanced Swift-XRT position
  54. GRB 251103B: Swift detection of a burst
  55. GRB 251103B: Fermi GBM Final Real-time Localization
  56. GRB 251103A: Swift/UVOT Detection
  57. GRB 251103A: Fermi GBM Observation
  58. GRB 251103A: SVOM/GRM observation
  59. GRB 251103A: Swift-XRT afterglow detection
  60. LIGO/Virgo/KAGRA S251031cq: Updated Sky localization
  61. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  62. EP251102a: Einstein Probe detection of a fast X-ray transient
  63. GRB 251025B: OHP/T193 optical upper limit
  64. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  65. GRB 251103A: LCO optical observation
  66. EP251102.890: COLIBRÍ optical counterpart candidate
  67. GRB 251103A: GOTO optical afterglow detection
  68. GRB 251102A: AstroSat CZTI detection
  69. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  70. GRB 251103A: NOT spectroscopic redshift z = 0.76
  71. GRB 251103A: BOOTES-2/TELMA optical afterglow
  72. GRB 251103A: LCO optical afterglow detection
  73. GRB 251103A: NOT optical afterglow candidate (duplicate submission)
  74. GRB 251103A: Fermi GBM Final Localization
  75. GRB 251103A: NOT optical afterglow candidate
  76. GRB 251103A: SVOM detection of a bright burst
  77. GRB 251102B: Fermi GBM Final Real-time Localization
  78. Fermi GRB 251102A: Global MASTER-Net observations report
  79. GRB 251102A: Fermi GBM Final Real-time Localization
  80. GRB 251031A: Fermi GBM Observation
  81. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  82. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  83. Konus-Wind detection of GRB 251028A
  84. GRB 251031A: BALROG localization (Fermi Trigger 783588065 / GRB 251031306)
  85. GRB 251031A: Fermi GBM Final Real-time Localization
  86. GRB 251025C: SVOM/GRM observation
  87. GRB 251028A: GECAM-B detection
  88. GRB 251028A: SVOM/GRM observation
  89. IceCube-251025A: Two Transient Candidates from the Zwicky Transient Facility
  90. GRB 251028A: Fermi GBM Observation
  91. GRB 251026B: SOAR Classification of GOTO25jgl/SN2025absf as a Type Ia supernova
  92. GRB 251022A: Swift-XRT confirmation of fading
  93. GRB 251026B: LBT near-infrared observations
  94. GRB 250926B: VZLUSAT-2 detection
  95. GRB 250926A: VZLUSAT-2 detection
  96. GRB 250925A: VZLUSAT-2 detection
  97. GRB 251026B: Fermi GBM Observation
  98. GRB 251026A/EP251026a: SVOM/VT optical counterpart
  99. GRB 251026A/EP251026a: EP-FXT follow-up observation
  100. The EP-WXT trigger 01709247588 is likely a flaring star

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