Skip to main content
New JavaScript client! 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. EP260628b: EP-WXT detection of an X-ray transient and EP-FXT follow-up observation
  2. Fermi trigger No 804738310: Global MASTER-Net observations report
  3. Fermi GRB 260703A: Global MASTER-Net observations report
  4. GRB 260703A: Fermi GBM Final Localization
  5. GRB 260610B: VLA detection
  6. GRB 260623A: Glowbug gamma-ray detection
  7. GRB 260614B: ATCA Radio Upper Limits
  8. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  9. Fermi trigger No 804552016: Global MASTER-Net observations report
  10. GRB 260701A: Fermi GBM Final Real-time Localization
  11. Fermi GBM trigger 804552016/260630945 is not a GRB
  12. Fermi-LAT Gamma-ray Observations of IceCube-260622A
  13. EP260628a: EP-FXT follow-up observation
  14. GRB 260629A: Fermi GBM Final Real-time Localization
  15. Fermi GRB 260628A: Global MASTER-Net observations report
  16. EP260628a: EP-WXT detection of a fast X-ray transient
  17. GRB 260628A: Fermi GBM Final Real-time Localization
  18. The EP-WXT trigger 01709272671 is likely a flaring star
  19. EP260626a: further Liverpool Telescope optical upper limits
  20. EP260626a: EP-FXT follow-up observation
  21. EP260626a: COLIBRÍ optical upper limit
  22. EP260626a: Liverpool Telescope upper limits
  23. EP260626a: EP-WXT detection of a fast X-ray transient
  24. Konus-Wind detection of GRB 260623B / EP260623a
  25. EP260623a: TNG NIR afterglow detection
  26. GRB 260618A: Fermi GBM Observation
  27. MASS-Cube (GRID 2.0) detection of GRB 260616B
  28. EP260623a: FTW optical and NIR observations
  29. GRB 260619A: SVOM/ECLAIRs refined analysis
  30. EP260623a: Liverpool Telescope optical observations
  31. Fermi GBM trigger 804010507/260624677 is not a GRB
  32. Konus-Wind detection of GRB 260618B
  33. GRB 260624A: Fermi GBM Final Real-time Localization (Duplicate Submission)
  34. GRB 260624A: Fermi GBM Final Real-time Localization
  35. EP260623a:refined analysis of the EP-WXT and EP-FXT observation
  36. EP260623a: WINTER J-band observations
  37. GRB 260617A: Glowbug gamma-ray detection of a short burst
  38. IceCube-260622A: Upper limits from a search for additional neutrino events in IceCube
  39. IPN triangulation of GRB 260605A
  40. EP260623a: Optical follow-up observations with Kinder
  41. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  42. GRB 260623A: Fermi GBM Final Real-time Localization
  43. EP260623a: SVOM/VT optical observations
  44. EP260623a: TRT optical observations
  45. EP260623a: REM optical/NIR afterglow detection
  46. EP 260623a: COLIBRÍ optical observations
  47. GRB 260616B/EP260616a: Insight-HXMT/HE detection
  48. EP260623a: OSIRIS+/GTC redshift z = 0.703
  49. EP260623a: Las Cumbres discovery of the optical counterpart
  50. EP260623a: Einstein Probe detection of an X-ray transient
  51. GRB 260614B: EP-FXT follow-up observation
  52. IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
  53. GRB 260618C: SVOM/ECLAIRs detection of a possible burst through on-ground search
  54. EP260618a: Liverpool Telescope optical observations
  55. GRB 260619A: NOT optical observations
  56. GRB 260618B: LCO optical observations
  57. The EP-WXT trigger 01709271197 is likely a flaring star
  58. EP260618a: JinShan optical observations
  59. GRB 260616B/EP260616a: SVOM/GRM detection of a burst
  60. GRB 260618B: Fermi GBM Observation
  61. IceCube-Cascade 260618A: Upper limits from a search for additional neutrino events in IceCube
  62. GRB 260619A: TRT optical counterpart confirmation
  63. GRB 260610B: Further GRANDMA Optical Observations and re-brightening detection
  64. GRB 260604B: 239Alferov CubeSat detection
  65. GRB 260604A: 239Alferov CubeSat detection
  66. GRB 260610B: VLT/FORS2 spectroscopic observation suggests the non-thermal nature of the optical rebrightening
  67. GRB 260619A: SVOM/VT optical counterpart confirmation
  68. Fermi-LAT Gamma-ray Observations of IceCube-260610A
  69. GRB 260618B: SVOM/VT optical candidate
  70. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  71. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  72. Konus-Wind detection of GRB 260617A
  73. GRB 260616B: AstroSat CZTI detection
  74. GRB 260616A: AstroSat CZTI detection
  75. GRB 260616A: SVOM/GRM observation
  76. EP260618a: OHP/T193 optical observations
  77. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  78. GRB 260619A: Kilonova-Catcher optical upper limit
  79. EP260618a: EP-FXT follow-up observation
  80. EP260618a: LCO optical counterpart confirmation
  81. GRB 260617A: CALET Gamma-Ray Burst Monitor detection
  82. EP260618a: COLIBRÍ optical counterpart candidate
  83. GRB 260616A: NuSTAR detection of prompt emission
  84. GRB 260614B: NuSTAR detection of prompt emission
  85. GRB 260619A: SVOM possible detection of a faint burst
  86. IceCube-260610A: Upper limits from a search for additional neutrino events in IceCube
  87. GRB 260618B: Fermi-LAT detection
  88. IPN triangulation of GRB 260617A (short)
  89. GRB 260610B/AT 2026owq: FTW optical and NIR observations
  90. GRB 260616A: Insight-HXMT detection
  91. GRB 260618B: Fermi GBM Final Real-time Localization
  92. EP260618a: EP-WXT detection of an X-ray transient
  93. GRB 260610B: AbAO optical observations
  94. EP260616a/GRB 260616B: EP-FXT follow-up observation
  95. GRB 260506B: cubesat Avion detection
  96. GRB 260616C: GECAM-B observation of a burst
  97. GRB 260618A: Fermi GBM Final Real-time Localization
  98. GRB 260617A: Fermi GBM Detection
  99. GRB 260616A: Fermi GBM Observation
  100. GRB 260617A: Fermi GBM Final Real-time Localization (Duplicate Submission)

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
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