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"

19089 results found.

  1. EP260409a: COLIBRÍ optical upper limits
  2. EP260409a: Einstein Probe detection of an X-ray transient
  3. EP260321a: VLA radio detection
  4. GRB 260402A: SVOM/ECLAIRs refined analysis
  5. EP260402a / GRB 260402A: Mephisto optical upper limits
  6. EP-WXT01709259586: Xinglong optical upper limit
  7. EP260403a: Mephisto optical upper limits
  8. EP260402a/GRB 260402A: Xinglong optical upper limit
  9. EP260405a: GMOS-N optical upper limits
  10. EP260405a: Einstein Probe detection of a fast X-ray transient
  11. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  12. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  13. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  14. The EP-WXT trigger 01709259586 is likely a flaring star
  15. GRB 260330B: SVOM/VT further optical observation
  16. EP260403a: LCO optical observations of the counterpart
  17. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  18. EP260403a: LCO optical counterpart detection
  19. EP260403a: COLIBRÍ optical counterpart candidate
  20. GRB 260330B: SVOM/VT optical candidate
  21. EP260403a: Einstein Probe detection of an X-ray transient
  22. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  23. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  24. EP260324A / AT 2026hir: COLIBRÍ optical observations
  25. GRB 260402A: WINTER J-band upper limit
  26. GRB260402A: GROWTH-India Telescope optical upper limit
  27. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  28. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  29. GRB 260401A: SVOM/GRM observation
  30. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  31. GRB 260402A: Kilonova-Catcher optical upper limit
  32. GRB 260402A: MASTER optical observations
  33. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  34. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  35. GRB 260402A: SVOM detection of a burst
  36. EP260329b: Mondy and Assy-Turgen optical upper limits
  37. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  38. EP260321a :Xinglong optical observations
  39. EP260327a: Xinglong optical upper limit
  40. GRB 260330B: SVOM/VT optical upper limits
  41. GRB 260321A: SVOM/ECLAIRs refined analysis
  42. EP260329b: J-band upper limits with WINTER
  43. EP260329a: J-band upper limit with WINTER
  44. GRB 260330B: LCO optical upper limits
  45. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  46. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  47. EP260329a: COLIBRÍ optical upper limit
  48. EP260329a: EP-FXT follow up observation
  49. EP260329a: NOT optical counterpart candidate
  50. EP260329b: Optical follow-up with Kinder observations
  51. EP 260329b: COLIBRÍ optical observations
  52. EP260329a: Optical upper limit with Kinder observations
  53. EP260329b: LCO optical observations of the counterpart
  54. EP260329b: Einstein Probe detection of an X-ray transient
  55. EP260329a: Einstein Probe detection of an X-ray transient
  56. EP-WXT trigger 01709259209: TRT optical counterpart detection
  57. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  58. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  59. EP260327a: SVOM/VT optical upper limits
  60. GRB 260307B: ATCA Radio Upper Limits
  61. EP260327a: WINTER J-band upper limit
  62. EP260327a: COLIBRÍ optical upper limits
  63. EP260327a: Gemini-North optical upper limits
  64. EP260324a: GROWTH-India Telescope optical observation
  65. EP260327a: Einstein Probe detection of an X-ray transient
  66. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  67. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  68. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  69. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  70. EP260321a: JinShan near-infrared observations
  71. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  72. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  73. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  74. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  75. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  76. EP260321a: COLIBRÍ further optical observations and brightening
  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. EP260321a: GOTO detection of blue variable source
  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. EP260321a: Las Cumbres upper limit
  84. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  85. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  86. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  87. EP260321a: SVOM/VT optical upper limit
  88. Fermi GBM Sub-Threshold Detection of GRB 260321A
  89. GRB 260321A: SVOM detection of a burst
  90. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  91. EP260321a: Einstein Probe detection of an X-ray transient
  92. GRB 260310A / AT 2026fgk: KAIT optical observations
  93. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  94. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  95. GRB 260318A: SVOM/GRM observation
  96. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  97. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  98. GRB 260310A / AT 2026fgk: radio detection with the VLA
  99. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  100. GRB 260310A / AT2026fgk: LCO 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