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"

26769 results found.

  1. EP260327a: WINTER J-band upper limit
  2. EP260327a: COLIBRÍ optical upper limits
  3. EP260327a: Gemini-North optical upper limits
  4. EP260324a: GROWTH-India Telescope optical observation
  5. EP260327a: Global MASTER-Net observations report
  6. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  7. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  8. The EP-WXT trigger 01709259173 is likely a flaring star
  9. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  10. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  11. GRB 260326A: Fermi GBM Detection
  12. GRB 260325A: Fermi GBM Final Localization
  13. GRB 260326A: Fermi GBM Final Real-time Localization
  14. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  15. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  16. IPN triangulation of GRB 260316B
  17. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  18. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  19. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  20. GRB 260310A: LBT optical observations
  21. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  22. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  23. The EP-WXT trigger 01709259112 is likely a flaring star
  24. Fermi GRB 260323A: Global MASTER-Net observations report
  25. GRB 260323A: Fermi GBM Final Real-time Localization
  26. GRB 260322A: Fermi GBM Final Localization
  27. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  28. EP260321a: COLIBRÍ further optical observations and brightening
  29. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  30. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  31. EP260214b: ATCA 6 GHz detection
  32. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  33. GRB 260321A: EP-FXT follow-up observation
  34. The EP-WXT trigger 01709259045 is likely a flaring star
  35. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  36. EP260321a: GOTO detection of blue variable source
  37. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  38. EP260321a: further Kinder optical observations
  39. GRB 260321A: SVOM/VT optical upper limits
  40. EP260321a: Las Cumbres upper limit
  41. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  42. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  43. EP260321a: SVOM/VT optical upper limit
  44. Fermi GBM Sub-Threshold Detection of GRB 260321A
  45. GRB 260321A: SVOM detection of a burst
  46. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  47. EP260321a: Global MASTER-Net observations report
  48. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  49. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  50. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  51. GRB 260310A/AT2026fgk: LBT near-infrared observations
  52. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  53. GRB 260318A: SVOM/GRM observation
  54. The EP-WXT trigger 01709258989 is likely a flaring star
  55. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  56. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  57. Fermi GRB 260318A: Global MASTER-Net observations report
  58. GRB 260318A: Fermi GBM Final Real-time Localization
  59. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  60. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  61. GRB 260310A / AT2026fgk: LCO optical observations
  62. GRB 260317A: Fermi GBM Final Localization
  63. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  64. EP260316a: COLIBRÍ faint optical counterpart candidate
  65. GRB 260316B: AstroSat CZTI detection
  66. EP260316a: Xinglong optical upper limit
  67. GRB 260316B: Fermi GBM Final Real-time Localization
  68. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  69. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  70. IceCube-260315A: COLIBRÍ optical observations
  71. EP260314a: Xinglong optical upper limit
  72. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  73. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  74. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  75. GRB 260310A / AT 2026fgk: iTelescope optical observations
  76. EP260314a: COLIBRÍ optical upper limit
  77. EP260314a: BOOTES-6/DPR optical upper limits at early times
  78. EP260314a: Global MASTER-Net observations report
  79. EP260314a: SVOM/VT optical candidate
  80. Fermi trigger No 795185313: Global MASTER-Net observations report
  81. IceCube Alert 260315A: Global MASTER-Net observations report
  82. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  83. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  84. GRB 260310A / AT2026fgk: SAO RAS optical observations
  85. GRB 260310A / AT2026fgk: TNG NIR detection
  86. GRB 260310A / AT2026fgk: OASDG optical observations
  87. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  88. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  89. Fermi GRB 260314A: Global MASTER-Net observations report
  90. Fermi GRB 260313A: Global MASTER-Net observations report
  91. GRB 260314A: Fermi GBM Final Real-time Localization
  92. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  93. GRB 260313A: A Correction to the Fermi GBM Final Localization
  94. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  95. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  96. GRB 260310A: NOT optical polarimetry
  97. Swift BAT trigger 1500295: A solar flare
  98. GRB 260313A: Fermi GBM Final Real-time Localization
  99. Swift BAT trigger 1500287: A solar flare
  100. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153

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