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"

11377 results found.

  1. EP-WXT01709259790: Optical Upper limits with kinder observations
  2. GRB 260410A: Fermi-LAT detection
  3. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  4. EP260409a: Einstein Probe detection of an X-ray transient
  5. GRB 260402A: SVOM/ECLAIRs refined analysis
  6. EP260402a / GRB 260402A: Mephisto optical upper limits
  7. EP260405a: Einstein Probe detection of a fast X-ray transient
  8. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  9. EP260403a: COLIBRÍ optical counterpart candidate
  10. EP260403a: Einstein Probe detection of an X-ray transient
  11. GRB 260403A: AstroSat CZTI detection
  12. GRB 260402C: AstroSat CZTI detection of a long burst
  13. EP260324A / AT 2026hir: COLIBRÍ optical observations
  14. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  15. GRB 260402A: SVOM detection of a burst
  16. Fermi GRB 260401A: Global MASTER-Net observations report
  17. GRB 260401A: MAXI/GSC detection
  18. EP260329b: Mondy and Assy-Turgen optical upper limits
  19. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  20. EP260327a: Xinglong optical upper limit
  21. EP260329b: GOTO detection of optical counterpart
  22. Konus-Wind detection of GRB 260320A
  23. Konus-Wind detection of GRB 260316B
  24. GRB 260330B: SVOM detection of a burst
  25. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  26. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  27. Fermi trigger No 796485221: Global MASTER-Net observations report
  28. EP260329b: Optical follow-up with Kinder observations
  29. EP260329a: Optical upper limit with Kinder observations
  30. EP260329b: Einstein Probe detection of an X-ray transient
  31. EP-WXT trigger 01709259209: TRT optical counterpart detection
  32. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  33. GRB 260327A: AstroSat CZTI detection of a long burst
  34. EP260327a: Global MASTER-Net observations report
  35. EP260327a: Einstein Probe detection of an X-ray transient
  36. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  37. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  38. GRID detection of GRB 260320A
  39. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  40. GRB 260320A: Glowbug gamma-ray detection
  41. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  42. EP260214b: ATCA 6 GHz detection
  43. EP260321a: further Kinder optical observations
  44. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  45. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  46. EP260321a: Einstein Probe detection of an X-ray transient
  47. GRB 260310A / AT 2026fgk: KAIT optical observations
  48. GRB 260320A: NuSTAR detection of prompt emission
  49. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  50. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  51. NOEMA Detection of GRB 260310A / AT 2026fgk
  52. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  53. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  54. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  55. GRB 260317A: Fermi GBM Final Localization
  56. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  57. GRB 260316B: AstroSat CZTI detection
  58. EP260316a: optical upper limit with Kinder observations
  59. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  60. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  61. EP260314a: optical upper limit with Kinder observations
  62. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  63. EP260314a: Global MASTER-Net observations report
  64. Fermi trigger No 795185313: Global MASTER-Net observations report
  65. EP260314a: Einstein Probe detection of an X-ray transient
  66. GRB 260310A/AT2026fgk: radio detection at 15GHz
  67. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  68. Fermi GRB 260314A: Global MASTER-Net observations report
  69. Fermi GRB 260313A: Global MASTER-Net observations report
  70. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  71. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  72. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  73. GRB 260312B: AstroSat CZTI detection
  74. Fermi GRB 260311B: Global MASTER-Net observations report
  75. GRB 260310A: AstroSat CZTI detection of a long burst
  76. Fermi GRB 260310B: Global MASTER-Net observations report
  77. Fermi GRB 260310A: Global MASTER-Net observations report
  78. GRB 260308A: Fermi GBM Final Real-time Localization
  79. Fermi GRB 260307A: Global MASTER-Net observations report
  80. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  81. EP260306a: Einstein Probe detection of an X-ray transient
  82. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  83. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  84. Fermi GRB 260305A: Global MASTER-Net observations report
  85. GRB 260303B: AstroSat CZTI detection
  86. GRB 260304A: AstroSat CZTI detection of a long burst
  87. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  88. GRB 260303B: NuSTAR detection of prompt emission
  89. GRB 260228A: SVOM/ECLAIRs refined analysis
  90. GRB 260225A: SVOM/ECLAIRs refined analysis
  91. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  92. GRB 260303B: Fermi GBM Final Real-time Localization
  93. EP260302a: analysis of the follow-up EP-FXT observation
  94. EP260302a: LCO observations
  95. EP260302a: BOOTES-7 optical counterpart detection at early times
  96. GRB 260303A: SVOM detection of a burst
  97. EP260302a: Einstein Probe detection of an X-ray transient
  98. EP260227a: Mondy optical observations
  99. EP260227a: Mephisto optical detection
  100. EP260227a: SVOM/VT optical 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