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"

41584 results found.

  1. The EP-WXT trigger 01709259621 is likely a flaring star
  2. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  3. The EP-WXT trigger 01709259615 is likely a flaring star
  4. Fermi trigger No 797039833: Global MASTER-Net observations report
  5. GRB 260403A: GECAM-B observation of a long burst
  6. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  7. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  8. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  9. The EP-WXT trigger 01709259586 is likely a flaring star
  10. GRB 260330B: SVOM/VT further optical observation
  11. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  12. GRB 260330B: SVOM/ECLAIRs refined analysis
  13. EP260403a: LCO optical observations of the counterpart
  14. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  15. EP260403a: LCO optical counterpart detection
  16. GRB 260330B: SVOM/VT optical candidate
  17. EP260403a: Einstein Probe detection of an X-ray transient
  18. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  19. GRB 260403A: AstroSat CZTI detection
  20. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  21. GRB 260402B: GECAM-B observation
  22. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  23. GRB 260402C: NuSTAR detection of prompt emission
  24. GRB 260402C: AstroSat CZTI detection of a long burst
  25. GRB 260403A: Fermi GBM Final Real-time Localization
  26. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  27. GRB 260402B: Fermi GBM Final Real-time Localization
  28. GRB 260402A: WINTER J-band upper limit
  29. GRB260402A: GROWTH-India Telescope optical upper limit
  30. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  31. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  32. GRB 260401A: SVOM/GRM observation
  33. GRB 260401A: GECAM-B observation
  34. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  35. GRB 260402A: Kilonova-Catcher optical upper limit
  36. GRB 260402A: MASTER optical observations
  37. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  38. GRB 260402A: SVOM detection of a burst
  39. Fermi GRB 260401A: Global MASTER-Net observations report
  40. GRB 260401A: Fermi GBM Observation
  41. GRB 260401A: NuSTAR detection of prompt emission
  42. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  43. GRB 260401A: MAXI/GSC detection
  44. GRB 260401A: Fermi GBM Final Real-time Localization
  45. EP260329b: Mondy and Assy-Turgen optical upper limits
  46. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  47. EP260321a :Xinglong optical observations
  48. EP260327a: Xinglong optical upper limit
  49. EP260329b: GOTO detection of optical counterpart
  50. GRB 260330B: SVOM/VT optical upper limits
  51. Konus-Wind detection of GRB 260320A
  52. Konus-Wind detection of GRB 260316B (duplicate submission)
  53. Konus-Wind detection of GRB 260316B
  54. GRB 260321A: SVOM/ECLAIRs refined analysis
  55. EP260329b: J-band upper limits with WINTER
  56. EP260329a: J-band upper limit with WINTER
  57. GRB 260330A: Glowbug gamma-ray detection
  58. GRB 260310A: VLA Multi-frequency Radio Observations
  59. Fermi GBM Sub-Threshold Detection of GRB 260330B
  60. GRB 260330B: LCO optical upper limits
  61. GRB 260330B: SVOM detection of a burst
  62. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  63. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  64. EP260329a: COLIBRÍ optical upper limit
  65. EP260329a: EP-FXT follow up observation
  66. EP260329a: NOT optical counterpart candidate
  67. GRB 260330A: Fermi GBM Final Real-time Localization
  68. EP260329b: Global MASTER-Net observations report
  69. Fermi trigger No 796485221: Global MASTER-Net observations report
  70. GRB 260327A: Insight-HXMT/HE detection
  71. EP260329b: Optical follow-up with Kinder observations
  72. EP260329a: Optical upper limit with Kinder observations
  73. EP260329b: LCO optical observations of the counterpart
  74. GRB 260326A: Insight-HXMT/HE detection
  75. EP260329b: Einstein Probe detection of an X-ray transient
  76. EP260329a: Einstein Probe detection of an X-ray transient
  77. EP-WXT trigger 01709259209: TRT optical counterpart detection
  78. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  79. GRID detection of GRB 260326A
  80. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  81. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  82. EP260327a: SVOM/VT optical upper limits
  83. SMA Detection of GRB 260310A / AT 2026fgk
  84. GRB 260307B: ATCA Radio Upper Limits
  85. EP260327a: WINTER J-band upper limit
  86. EP260327a: COLIBRÍ optical upper limits
  87. GRB 260327A: AstroSat CZTI detection of a long burst
  88. EP260327a: Gemini-North optical upper limits
  89. EP260324a: GROWTH-India Telescope optical observation
  90. EP260327a: Global MASTER-Net observations report
  91. EP260327a: Einstein Probe detection of an X-ray transient
  92. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  93. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  94. The EP-WXT trigger 01709259173 is likely a flaring star
  95. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  96. IPN triangulation of GRB 260320A
  97. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  98. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  99. GRB 260326A: Fermi GBM Detection
  100. EP260321a: JinShan near-infrared 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