Skip to main content
Updates to LVK & CHIME Notices, Schema v7.2.3! 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"

37112 results found.

  1. EP260321A: Mondy optical observations
  2. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  3. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  4. Fermi GRB 260323A: Global MASTER-Net observations report
  5. GRB 260323A: Fermi GBM Final Real-time Localization
  6. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  7. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  8. GRB 260322A: Fermi GBM Final Localization
  9. GRB 260320A: Glowbug gamma-ray detection
  10. EP260321a: COLIBRÍ further optical observations and brightening
  11. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  12. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  13. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  14. GRB 260321A: EP-FXT follow-up observation
  15. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  16. EP260321a: further Kinder optical observations
  17. GRB 260321A: SVOM/VT optical upper limits
  18. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  19. GRB 260320A: Insight-HXMT/HE detection
  20. GRB 260310A: continued optical observation at Mondy
  21. Fermi GBM Sub-Threshold Detection of GRB 260321A
  22. GRB 260321A: SVOM detection of a burst
  23. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  24. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  25. GRB 260318A: Glowbug gamma-ray detection
  26. GRB 260310A / AT 2026fgk: KAIT optical observations
  27. GRB 260320A: NuSTAR detection of prompt emission
  28. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  29. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  30. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  31. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  32. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  33. GRB 260310A/AT2026fgk: LBT near-infrared observations
  34. NOEMA Detection of GRB 260310A / AT 2026fgk
  35. GRB 260318A: SVOM/GRM observation
  36. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  37. GRB 260318A: GECAM-B observation
  38. Fermi GRB 260318A: Global MASTER-Net observations report
  39. GRB 260318A: Fermi GBM Final Real-time Localization
  40. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  41. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  42. GRB 260310A / AT 2026fgk: radio detection with the VLA
  43. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  44. GRB 260310A / AT2026fgk: LCO optical observations
  45. GRB 260317A: Fermi GBM Final Localization
  46. GRB 260316B: GECAM-B observation
  47. GRB 260316B: SVOM/GRM observation
  48. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  49. GRB 260316B: AstroSat CZTI detection
  50. GRB 260316B: Fermi GBM Final Real-time Localization
  51. EP260316a: optical upper limit with Kinder observations
  52. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  53. GRB 260314A: Glowbug gamma-ray detection
  54. EP260314a: optical upper limit with Kinder observations
  55. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  56. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  57. GRB 260310A / AT 2026fgk: iTelescope optical observations
  58. GRID detection of GRB 260312B
  59. EP260314a: BOOTES-6/DPR optical upper limits at early times
  60. GRB 260314A: GECAM-B observation of a burst
  61. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  62. GRB 260310A / AT2026fgk: SAO RAS optical observations
  63. GRB 260310A/AT2026fgk: radio detection at 15GHz
  64. GRB 260310A / AT2026fgk: TNG NIR detection
  65. GRB 260310A / AT2026fgk: OASDG optical observations
  66. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  67. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  68. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  69. Fermi GRB 260314A: Global MASTER-Net observations report
  70. Fermi GRB 260313A: Global MASTER-Net observations report
  71. GRB 260314A: Fermi GBM Final Real-time Localization
  72. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  73. GRB 260313A: A Correction to the Fermi GBM Final Localization
  74. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  75. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  76. GRB 260310B: Insight-HXMT/HE detection
  77. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  78. GRB 260310A: NOT optical polarimetry
  79. GRB 260312B: AstroSat CZTI detection
  80. Swift BAT trigger 1500295: A solar flare
  81. GRB 260313A: Fermi GBM Final Real-time Localization
  82. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  83. Swift BAT trigger 1500287: A solar flare
  84. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  85. GRB 260308A: Insight-HXMT/HE detection
  86. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  87. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  88. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  89. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  90. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  91. GRB260310A / AT2026fgk: P200 Spectroscopy
  92. GRB 260312B: Glowbug gamma-ray detection
  93. GRB 260310A: Fermi GBM Observation
  94. GRB 260310A: potential optical counterpart
  95. Fermi GRB 260312B: Global MASTER-Net observations report
  96. Fermi GRB 260311B: Global MASTER-Net observations report
  97. Swift BAT trigger 1500148: A solar flare
  98. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  99. GRB 260312B: Fermi GBM Final Real-time Localization
  100. GRB 260310B: GECAM-B observation of a burst

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
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