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. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  2. GRB 260402C: NuSTAR detection of prompt emission
  3. GRB 260402C: AstroSat CZTI detection of a long burst
  4. EP260324A / AT 2026hir: COLIBRÍ optical observations
  5. GRB 260403A: Fermi GBM Final Real-time Localization
  6. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  7. GRB 260402B: Fermi GBM Final Real-time Localization
  8. GRB 260402A: WINTER J-band upper limit
  9. GRB260402A: GROWTH-India Telescope optical upper limit
  10. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  11. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  12. GRB 260401A: SVOM/GRM observation
  13. GRB 260401A: GECAM-B observation
  14. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  15. GRB 260402A: Kilonova-Catcher optical upper limit
  16. GRB 260402A: MASTER optical observations
  17. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  18. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  19. GRB 260402A: SVOM detection of a burst
  20. Fermi GRB 260401A: Global MASTER-Net observations report
  21. GRB 260401A: Fermi GBM Observation
  22. GRB 260401A: NuSTAR detection of prompt emission
  23. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  24. GRB 260401A: MAXI/GSC detection
  25. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  26. GRB 260401A: Fermi GBM Final Real-time Localization
  27. EP260329b: Mondy and Assy-Turgen optical upper limits
  28. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  29. EP260321a :Xinglong optical observations
  30. EP260327a: Xinglong optical upper limit
  31. EP260329b: GOTO detection of optical counterpart
  32. GRB 260330B: SVOM/VT optical upper limits
  33. Konus-Wind detection of GRB 260320A
  34. Konus-Wind detection of GRB 260316B (duplicate submission)
  35. Konus-Wind detection of GRB 260316B
  36. GRB 260321A: SVOM/ECLAIRs refined analysis
  37. EP260329b: J-band upper limits with WINTER
  38. EP260329a: J-band upper limit with WINTER
  39. GRB 260330A: Glowbug gamma-ray detection
  40. GRB 260310A: VLA Multi-frequency Radio Observations
  41. Fermi GBM Sub-Threshold Detection of GRB 260330B
  42. GRB 260330B: LCO optical upper limits
  43. GRB 260330B: SVOM detection of a burst
  44. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  45. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  46. EP260329a: COLIBRÍ optical upper limit
  47. EP260329a: EP-FXT follow up observation
  48. EP260329a: NOT optical counterpart candidate
  49. GRB 260330A: Fermi GBM Final Real-time Localization
  50. EP260329b: Global MASTER-Net observations report
  51. Fermi trigger No 796485221: Global MASTER-Net observations report
  52. GRB 260327A: Insight-HXMT/HE detection
  53. EP260329b: Optical follow-up with Kinder observations
  54. EP 260329b: COLIBRÍ optical observations
  55. EP260329a: Optical upper limit with Kinder observations
  56. EP260329b: LCO optical observations of the counterpart
  57. GRB 260326A: Insight-HXMT/HE detection
  58. EP260329b: Einstein Probe detection of an X-ray transient
  59. EP260329a: Einstein Probe detection of an X-ray transient
  60. EP-WXT trigger 01709259209: TRT optical counterpart detection
  61. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  62. GRID detection of GRB 260326A
  63. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  64. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  65. EP260327a: SVOM/VT optical upper limits
  66. SMA Detection of GRB 260310A / AT 2026fgk
  67. GRB 260307B: ATCA Radio Upper Limits
  68. EP260327a: WINTER J-band upper limit
  69. EP260327a: COLIBRÍ optical upper limits
  70. GRB 260327A: AstroSat CZTI detection of a long burst
  71. EP260327a: Gemini-North optical upper limits
  72. EP260324a: GROWTH-India Telescope optical observation
  73. EP260327a: Global MASTER-Net observations report
  74. EP260327a: Einstein Probe detection of an X-ray transient
  75. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  76. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  77. The EP-WXT trigger 01709259173 is likely a flaring star
  78. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  79. IPN triangulation of GRB 260320A
  80. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  81. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  82. GRB 260326A: Fermi GBM Detection
  83. EP260321a: JinShan near-infrared observations
  84. GRB 260325A: Fermi GBM Final Localization
  85. GRB 260326A: Fermi GBM Final Real-time Localization
  86. EP260321a: Upper limits from a neutrino search with IceCube
  87. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  88. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  89. IPN triangulation of GRB 260316B
  90. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  91. GRID detection of GRB 260320A
  92. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  93. EP260321a: Gemini-South confirmation of a supernova
  94. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  95. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  96. GRB 260310A: LBT optical observations
  97. EP260321A: Mondy optical observations
  98. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  99. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  100. GRB 260316B: CALET Gamma-Ray Burst Monitor detection

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