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. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  2. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  3. GRB 260322A: Fermi GBM Final Localization
  4. GRB 260320A: Glowbug gamma-ray detection
  5. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  6. EP260321a: COLIBRÍ further optical observations and brightening
  7. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  8. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  9. EP260214b: ATCA 6 GHz detection
  10. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  11. GRB 260321A: EP-FXT follow-up observation
  12. The EP-WXT trigger 01709259045 is likely a flaring star
  13. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  14. EP260321a: GOTO detection of blue variable source
  15. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  16. EP260321a: further Kinder optical observations
  17. GRB 260321A: SVOM/VT optical upper limits
  18. EP260321a: Las Cumbres upper limit
  19. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  20. GRB 260320A: Insight-HXMT/HE detection
  21. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  22. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  23. EP260321a: SVOM/VT optical upper limit
  24. GRB 260310A: continued optical observation at Mondy
  25. Fermi GBM Sub-Threshold Detection of GRB 260321A
  26. GRB 260321A: SVOM detection of a burst
  27. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  28. EP260321a: Global MASTER-Net observations report
  29. EP260321a: Einstein Probe detection of an X-ray transient
  30. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  31. GRB 260318A: Glowbug gamma-ray detection
  32. GRB 260310A / AT 2026fgk: KAIT optical observations
  33. GRB 260320A: NuSTAR detection of prompt emission
  34. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  35. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  36. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  37. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  38. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  39. GRB 260310A/AT2026fgk: LBT near-infrared observations
  40. NOEMA Detection of GRB 260310A / AT 2026fgk
  41. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  42. GRB 260318A: SVOM/GRM observation
  43. The EP-WXT trigger 01709258989 is likely a flaring star
  44. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  45. GRB 260318A: GECAM-B observation
  46. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  47. Fermi GRB 260318A: Global MASTER-Net observations report
  48. GRB 260318A: Fermi GBM Final Real-time Localization
  49. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  50. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  51. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  52. GRB 260310A / AT 2026fgk: radio detection with the VLA
  53. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  54. GRB 260310A / AT2026fgk: LCO optical observations
  55. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  56. GRB 260317A: Fermi GBM Final Localization
  57. GRB 260316B: GECAM-B observation
  58. GRB 260316B: SVOM/GRM observation
  59. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  60. EP260316a: COLIBRÍ faint optical counterpart candidate
  61. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  62. GRB 260316B: AstroSat CZTI detection
  63. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  64. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  65. EP260316a: Xinglong optical upper limit
  66. GRB 260316B: Fermi GBM Final Real-time Localization
  67. EP260316a: optical upper limit with Kinder observations
  68. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  69. GRB 260314A: Glowbug gamma-ray detection
  70. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  71. IceCube-260315A: COLIBRÍ optical observations
  72. EP260314a: Xinglong optical upper limit
  73. EP260314a: optical upper limit with Kinder observations
  74. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  75. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  76. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  77. GRB 260310A / AT 2026fgk: iTelescope optical observations
  78. EP260314a: COLIBRÍ optical upper limit
  79. GRID detection of GRB 260312B
  80. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  81. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  82. EP260314a: BOOTES-6/DPR optical upper limits at early times
  83. EP260314a: Global MASTER-Net observations report
  84. EP260314a: SVOM/VT optical candidate
  85. Fermi trigger No 795185313: Global MASTER-Net observations report
  86. IceCube Alert 260315A: Global MASTER-Net observations report
  87. EP260314a: Einstein Probe detection of an X-ray transient
  88. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  89. GRB 260314A: GECAM-B observation of a burst
  90. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  91. GRB 260310A / AT2026fgk: SAO RAS optical observations
  92. GRB 260310A/AT2026fgk: radio detection at 15GHz
  93. GRB 260310A / AT2026fgk: TNG NIR detection
  94. GRB 260310A / AT2026fgk: OASDG optical observations
  95. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  96. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  97. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  98. Fermi GRB 260314A: Global MASTER-Net observations report
  99. Fermi GRB 260313A: Global MASTER-Net observations report
  100. GRB 260314A: Fermi GBM Final Real-time Localization

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