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"

36277 results found.

  1. GRB 260402C: NuSTAR detection of prompt emission
  2. GRB 260402C: AstroSat CZTI detection of a long burst
  3. GRB 260403A: Fermi GBM Final Real-time Localization
  4. GRB 260402B: Fermi GBM Final Real-time Localization
  5. GRB 260402A: WINTER J-band upper limit
  6. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  7. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  8. GRB 260401A: SVOM/GRM observation
  9. GRB 260401A: GECAM-B observation
  10. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  11. GRB 260402A: Kilonova-Catcher optical upper limit
  12. GRB 260402A: MASTER optical observations
  13. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  14. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  15. GRB 260402A: SVOM detection of a burst
  16. Fermi GRB 260401A: Global MASTER-Net observations report
  17. GRB 260401A: Fermi GBM Observation
  18. GRB 260401A: NuSTAR detection of prompt emission
  19. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  20. GRB 260401A: MAXI/GSC detection
  21. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  22. GRB 260401A: Fermi GBM Final Real-time Localization
  23. EP260329b: Mondy and Assy-Turgen optical upper limits
  24. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  25. EP260321a :Xinglong optical observations
  26. EP260329b: GOTO detection of optical counterpart
  27. GRB 260330B: SVOM/VT optical upper limits
  28. Konus-Wind detection of GRB 260320A
  29. Konus-Wind detection of GRB 260316B (duplicate submission)
  30. Konus-Wind detection of GRB 260316B
  31. GRB 260321A: SVOM/ECLAIRs refined analysis
  32. EP260329b: J-band upper limits with WINTER
  33. EP260329a: J-band upper limit with WINTER
  34. GRB 260330A: Glowbug gamma-ray detection
  35. GRB 260310A: VLA Multi-frequency Radio Observations
  36. Fermi GBM Sub-Threshold Detection of GRB 260330B
  37. GRB 260330B: LCO optical upper limits
  38. GRB 260330B: SVOM detection of a burst
  39. GRB 260330A: Fermi GBM Final Real-time Localization
  40. GRB 260327A: Insight-HXMT/HE detection
  41. EP260329b: Optical follow-up with Kinder observations
  42. EP260329a: Optical upper limit with Kinder observations
  43. GRB 260326A: Insight-HXMT/HE detection
  44. GRID detection of GRB 260326A
  45. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  46. SMA Detection of GRB 260310A / AT 2026fgk
  47. GRB 260307B: ATCA Radio Upper Limits
  48. GRB 260327A: AstroSat CZTI detection of a long burst
  49. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  50. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  51. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  52. IPN triangulation of GRB 260320A
  53. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  54. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  55. GRB 260326A: Fermi GBM Detection
  56. GRB 260325A: Fermi GBM Final Localization
  57. GRB 260326A: Fermi GBM Final Real-time Localization
  58. EP260321a: Upper limits from a neutrino search with IceCube
  59. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  60. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  61. IPN triangulation of GRB 260316B
  62. GRID detection of GRB 260320A
  63. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  64. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  65. GRB 260310A: LBT optical observations
  66. EP260321A: Mondy optical observations
  67. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  68. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  69. Fermi GRB 260323A: Global MASTER-Net observations report
  70. GRB 260323A: Fermi GBM Final Real-time Localization
  71. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  72. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  73. GRB 260322A: Fermi GBM Final Localization
  74. GRB 260320A: Glowbug gamma-ray detection
  75. EP260321a: COLIBRÍ further optical observations and brightening
  76. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  77. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  78. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  79. GRB 260321A: EP-FXT follow-up observation
  80. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  81. EP260321a: further Kinder optical observations
  82. GRB 260321A: SVOM/VT optical upper limits
  83. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  84. GRB 260320A: Insight-HXMT/HE detection
  85. GRB 260310A: continued optical observation at Mondy
  86. Fermi GBM Sub-Threshold Detection of GRB 260321A
  87. GRB 260321A: SVOM detection of a burst
  88. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  89. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  90. GRB 260318A: Glowbug gamma-ray detection
  91. GRB 260310A / AT 2026fgk: KAIT optical observations
  92. GRB 260320A: NuSTAR detection of prompt emission
  93. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  94. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  95. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  96. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  97. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  98. GRB 260310A/AT2026fgk: LBT near-infrared observations
  99. NOEMA Detection of GRB 260310A / AT 2026fgk
  100. GRB 260318A: SVOM/GRM observation

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