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"
  1. EP260403a: COLIBRÍ optical counterpart candidate
  2. GRB 260330B: SVOM/VT optical candidate
  3. EP260403a: Einstein Probe detection of an X-ray transient
  4. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  5. GRB 260403A: AstroSat CZTI detection
  6. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  7. GRB 260402B: GECAM-B observation
  8. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  9. GRB 260402C: NuSTAR detection of prompt emission
  10. GRB 260402C: AstroSat CZTI detection of a long burst
  11. EP260324A / AT 2026hir: COLIBRÍ optical observations
  12. GRB 260403A: Fermi GBM Final Real-time Localization
  13. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  14. GRB 260402B: Fermi GBM Final Real-time Localization
  15. GRB 260402A: WINTER J-band upper limit
  16. GRB260402A: GROWTH-India Telescope optical upper limit
  17. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  18. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  19. GRB 260401A: SVOM/GRM observation
  20. GRB 260401A: GECAM-B observation
  21. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  22. GRB 260402A: Kilonova-Catcher optical upper limit
  23. GRB 260402A: MASTER optical observations
  24. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  25. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  26. GRB 260402A: SVOM detection of a burst
  27. Fermi GRB 260401A: Global MASTER-Net observations report
  28. GRB 260401A: Fermi GBM Observation
  29. GRB 260401A: NuSTAR detection of prompt emission
  30. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  31. GRB 260401A: MAXI/GSC detection
  32. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  33. GRB 260401A: Fermi GBM Final Real-time Localization
  34. EP260329b: Mondy and Assy-Turgen optical upper limits
  35. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  36. EP260321a :Xinglong optical observations
  37. EP260327a: Xinglong optical upper limit
  38. EP260329b: GOTO detection of optical counterpart
  39. GRB 260330B: SVOM/VT optical upper limits
  40. Konus-Wind detection of GRB 260320A
  41. Konus-Wind detection of GRB 260316B (duplicate submission)
  42. Konus-Wind detection of GRB 260316B
  43. GRB 260321A: SVOM/ECLAIRs refined analysis
  44. EP260329b: J-band upper limits with WINTER
  45. EP260329a: J-band upper limit with WINTER
  46. GRB 260330A: Glowbug gamma-ray detection
  47. GRB 260310A: VLA Multi-frequency Radio Observations
  48. Fermi GBM Sub-Threshold Detection of GRB 260330B
  49. GRB 260330B: LCO optical upper limits
  50. GRB 260330B: SVOM detection of a burst
  51. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  52. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  53. EP260329a: COLIBRÍ optical upper limit
  54. EP260329a: EP-FXT follow up observation
  55. EP260329a: NOT optical counterpart candidate
  56. GRB 260330A: Fermi GBM Final Real-time Localization
  57. EP260329b: Global MASTER-Net observations report
  58. Fermi trigger No 796485221: Global MASTER-Net observations report
  59. GRB 260327A: Insight-HXMT/HE detection
  60. EP260329b: Optical follow-up with Kinder observations
  61. EP 260329b: COLIBRÍ optical observations
  62. EP260329a: Optical upper limit with Kinder observations
  63. EP260329b: LCO optical observations of the counterpart
  64. GRB 260326A: Insight-HXMT/HE detection
  65. EP260329b: Einstein Probe detection of an X-ray transient
  66. EP260329a: Einstein Probe detection of an X-ray transient
  67. EP-WXT trigger 01709259209: TRT optical counterpart detection
  68. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  69. GRID detection of GRB 260326A
  70. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  71. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  72. EP260327a: SVOM/VT optical upper limits
  73. SMA Detection of GRB 260310A / AT 2026fgk
  74. GRB 260307B: ATCA Radio Upper Limits
  75. EP260327a: WINTER J-band upper limit
  76. EP260327a: COLIBRÍ optical upper limits
  77. GRB 260327A: AstroSat CZTI detection of a long burst
  78. EP260327a: Gemini-North optical upper limits
  79. EP260324a: GROWTH-India Telescope optical observation
  80. EP260327a: Global MASTER-Net observations report
  81. EP260327a: Einstein Probe detection of an X-ray transient
  82. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  83. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  84. The EP-WXT trigger 01709259173 is likely a flaring star
  85. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  86. IPN triangulation of GRB 260320A
  87. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  88. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  89. GRB 260326A: Fermi GBM Detection
  90. EP260321a: JinShan near-infrared observations
  91. GRB 260325A: Fermi GBM Final Localization
  92. GRB 260326A: Fermi GBM Final Real-time Localization
  93. EP260321a: Upper limits from a neutrino search with IceCube
  94. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  95. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  96. IPN triangulation of GRB 260316B
  97. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  98. GRID detection of GRB 260320A
  99. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  100. EP260321a: Gemini-South confirmation of a supernova

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