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. NOEMA Detection of GRB 260310A / AT 2026fgk
  2. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  3. GRB 260318A: SVOM/GRM observation
  4. The EP-WXT trigger 01709258989 is likely a flaring star
  5. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  6. GRB 260318A: GECAM-B observation
  7. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  8. Fermi GRB 260318A: Global MASTER-Net observations report
  9. GRB 260318A: Fermi GBM Final Real-time Localization
  10. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  11. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  12. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  13. GRB 260310A / AT 2026fgk: radio detection with the VLA
  14. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  15. GRB 260310A / AT2026fgk: LCO optical observations
  16. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  17. GRB 260317A: Fermi GBM Final Localization
  18. GRB 260316B: GECAM-B observation
  19. GRB 260316B: SVOM/GRM observation
  20. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  21. EP260316a: COLIBRÍ faint optical counterpart candidate
  22. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  23. GRB 260316B: AstroSat CZTI detection
  24. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  25. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  26. EP260316a: Xinglong optical upper limit
  27. GRB 260316B: Fermi GBM Final Real-time Localization
  28. EP260316a: optical upper limit with Kinder observations
  29. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  30. GRB 260314A: Glowbug gamma-ray detection
  31. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  32. IceCube-260315A: COLIBRÍ optical observations
  33. EP260314a: Xinglong optical upper limit
  34. EP260314a: optical upper limit with Kinder observations
  35. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  36. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  37. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  38. GRB 260310A / AT 2026fgk: iTelescope optical observations
  39. EP260314a: COLIBRÍ optical upper limit
  40. GRID detection of GRB 260312B
  41. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  42. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  43. EP260314a: BOOTES-6/DPR optical upper limits at early times
  44. EP260314a: Global MASTER-Net observations report
  45. EP260314a: SVOM/VT optical candidate
  46. Fermi trigger No 795185313: Global MASTER-Net observations report
  47. IceCube Alert 260315A: Global MASTER-Net observations report
  48. EP260314a: Einstein Probe detection of an X-ray transient
  49. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  50. GRB 260314A: GECAM-B observation of a burst
  51. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  52. GRB 260310A / AT2026fgk: SAO RAS optical observations
  53. GRB 260310A/AT2026fgk: radio detection at 15GHz
  54. GRB 260310A / AT2026fgk: TNG NIR detection
  55. GRB 260310A / AT2026fgk: OASDG optical observations
  56. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  57. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  58. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  59. Fermi GRB 260314A: Global MASTER-Net observations report
  60. Fermi GRB 260313A: Global MASTER-Net observations report
  61. GRB 260314A: Fermi GBM Final Real-time Localization
  62. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  63. GRB 260313A: A Correction to the Fermi GBM Final Localization
  64. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  65. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  66. GRB 260310B: Insight-HXMT/HE detection
  67. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  68. GRB 260310A: NOT optical polarimetry
  69. GRB 260312B: AstroSat CZTI detection
  70. Swift BAT trigger 1500295: A solar flare
  71. GRB 260313A: Fermi GBM Final Real-time Localization
  72. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  73. Swift BAT trigger 1500287: A solar flare
  74. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  75. GRB 260308A: Insight-HXMT/HE detection
  76. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  77. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  78. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  79. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  80. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  81. GRB260310A / AT2026fgk: P200 Spectroscopy
  82. GRB 260312B: Glowbug gamma-ray detection
  83. GRB 260310A: Fermi GBM Observation
  84. GRB 260310A: potential optical counterpart
  85. Fermi GRB 260312B: Global MASTER-Net observations report
  86. Fermi GRB 260311B: Global MASTER-Net observations report
  87. Swift BAT trigger 1500148: A solar flare
  88. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  89. GRB 260312B: Fermi GBM Final Real-time Localization
  90. The EP-WXT trigger 01709258843 is not a real source
  91. GRB 260310B: GECAM-B observation of a burst
  92. Retraction of GCN 43965: GRB is actually solar flare
  93. GRB 260312A: Swift detection of a burst
  94. GRB 260311B: Fermi GBM Final Real-time Localization
  95. GRB 260131A/B: radio detection with the VLA
  96. EP260302a: MeerKAT radio counterpart
  97. GRB260307A: GECAM-B observation of a burst
  98. GRB 260308A: SVOM/GRM observation of a short GRB
  99. EP260306a: Mondy optical upper limit
  100. GRB 260310A: AstroSat CZTI detection of a long burst

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