Skip to main content
Retirement of GCN Classic VOEvent Brokers. 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"

27148 results found.

  1. GRB 260401A: Fermi GBM Final Real-time Localization
  2. EP260329b: Mondy and Assy-Turgen optical upper limits
  3. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  4. EP260321a :Xinglong optical observations
  5. EP260327a: Xinglong optical upper limit
  6. GRB 260330B: SVOM/VT optical upper limits
  7. Konus-Wind detection of GRB 260320A
  8. GRB 260321A: SVOM/ECLAIRs refined analysis
  9. EP260329b: J-band upper limits with WINTER
  10. EP260329a: J-band upper limit with WINTER
  11. GRB 260330A: Glowbug gamma-ray detection
  12. Fermi GBM Sub-Threshold Detection of GRB 260330B
  13. GRB 260330B: LCO optical upper limits
  14. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  15. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  16. EP260329a: COLIBRÍ optical upper limit
  17. EP260329a: EP-FXT follow up observation
  18. EP260329a: NOT optical counterpart candidate
  19. EP260329b: Global MASTER-Net observations report
  20. Fermi trigger No 796485221: Global MASTER-Net observations report
  21. GRB 260327A: Insight-HXMT/HE detection
  22. EP260329b: Optical follow-up with Kinder observations
  23. EP 260329b: COLIBRÍ optical observations
  24. EP260329a: Optical upper limit with Kinder observations
  25. EP260329b: LCO optical observations of the counterpart
  26. GRB 260326A: Insight-HXMT/HE detection
  27. EP260329b: Einstein Probe detection of an X-ray transient
  28. EP260329a: Einstein Probe detection of an X-ray transient
  29. EP-WXT trigger 01709259209: TRT optical counterpart detection
  30. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  31. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  32. EP260327a: SVOM/VT optical upper limits
  33. EP260327a: WINTER J-band upper limit
  34. EP260327a: COLIBRÍ optical upper limits
  35. EP260327a: Gemini-North optical upper limits
  36. EP260324a: GROWTH-India Telescope optical observation
  37. EP260327a: Global MASTER-Net observations report
  38. EP260327a: Einstein Probe detection of an X-ray transient
  39. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  40. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  41. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  42. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  43. GRB 260326A: Fermi GBM Detection
  44. EP260321a: JinShan near-infrared observations
  45. EP260321a: Upper limits from a neutrino search with IceCube
  46. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  47. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  48. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  49. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  50. Fermi GRB 260323A: Global MASTER-Net observations report
  51. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  52. GRB 260320A: Glowbug gamma-ray detection
  53. EP260321a: COLIBRÍ further optical observations and brightening
  54. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  55. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  56. GRB 260321A: EP-FXT follow-up observation
  57. EP260321a: GOTO detection of blue variable source
  58. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  59. EP260321a: further Kinder optical observations
  60. GRB 260321A: SVOM/VT optical upper limits
  61. EP260321a: Las Cumbres upper limit
  62. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  63. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  64. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  65. EP260321a: SVOM/VT optical upper limit
  66. Fermi GBM Sub-Threshold Detection of GRB 260321A
  67. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  68. EP260321a: Global MASTER-Net observations report
  69. EP260321a: Einstein Probe detection of an X-ray transient
  70. GRB 260318A: Glowbug gamma-ray detection
  71. GRB 260310A / AT 2026fgk: KAIT optical observations
  72. GRB 260320A: NuSTAR detection of prompt emission
  73. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  74. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  75. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  76. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  77. GRB 260318A: SVOM/GRM observation
  78. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  79. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  80. Fermi GRB 260318A: Global MASTER-Net observations report
  81. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  82. GRB 260310A / AT 2026fgk: radio detection with the VLA
  83. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  84. GRB 260310A / AT2026fgk: LCO optical observations
  85. GRB 260316B: SVOM/GRM observation
  86. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  87. EP260316a: COLIBRÍ faint optical counterpart candidate
  88. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  89. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  90. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  91. EP260316a: Xinglong optical upper limit
  92. EP260316a: optical upper limit with Kinder observations
  93. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  94. GRB 260314A: Glowbug gamma-ray detection
  95. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  96. IceCube-260315A: COLIBRÍ optical observations
  97. EP260314a: Xinglong optical upper limit
  98. EP260314a: optical upper limit with Kinder observations
  99. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  100. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations

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