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"
  1. GRB 260327A: Insight-HXMT/HE detection
  2. EP260329b: Optical follow-up with Kinder observations
  3. EP260329a: Optical upper limit with Kinder observations
  4. EP260329b: LCO optical observations of the counterpart
  5. EP260329b: Einstein Probe detection of an X-ray transient
  6. EP260329a: Einstein Probe detection of an X-ray transient
  7. EP-WXT trigger 01709259209: TRT optical counterpart detection
  8. GRID detection of GRB 260326A
  9. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  10. EP260327a: SVOM/VT optical upper limits
  11. SMA Detection of GRB 260310A / AT 2026fgk
  12. EP260327a: WINTER J-band upper limit
  13. EP260327a: COLIBRÍ optical upper limits
  14. GRB 260327A: AstroSat CZTI detection of a long burst
  15. EP260327a: Gemini-North optical upper limits
  16. EP260324a: GROWTH-India Telescope optical observation
  17. EP260327a: Global MASTER-Net observations report
  18. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  19. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  20. IPN triangulation of GRB 260320A
  21. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  22. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  23. GRB 260325A: Fermi GBM Final Localization
  24. GRB 260326A: Fermi GBM Final Real-time Localization
  25. EP260321a: Upper limits from a neutrino search with IceCube
  26. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  27. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  28. GRID detection of GRB 260320A
  29. EP260321a: Gemini-South confirmation of a supernova (duplicate submission)
  30. EP260321a: Gemini-South confirmation of a supernova
  31. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  32. EP260321A: Mondy optical observations
  33. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  34. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  35. Fermi GRB 260323A: Global MASTER-Net observations report
  36. GRB 260323A: Fermi GBM Final Real-time Localization
  37. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  38. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  39. GRB 260322A: Fermi GBM Final Localization
  40. GRB 260320A: Glowbug gamma-ray detection
  41. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  42. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  43. EP260214b: ATCA 6 GHz detection
  44. GRB 260321A: EP-FXT follow-up observation
  45. The EP-WXT trigger 01709259045 is likely a flaring star
  46. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  47. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  48. EP260321a: further Kinder optical observations
  49. EP260321a: Las Cumbres upper limit
  50. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  51. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  52. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  53. GRB 260310A: continued optical observation at Mondy
  54. Fermi GBM Sub-Threshold Detection of GRB 260321A
  55. GRB 260321A: SVOM detection of a burst
  56. EP260321a: Einstein Probe detection of an X-ray transient
  57. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  58. GRB 260310A / AT 2026fgk: KAIT optical observations
  59. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  60. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  61. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  62. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  63. GRB 260318A: SVOM/GRM observation
  64. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  65. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  66. Fermi GRB 260318A: Global MASTER-Net observations report
  67. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  68. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  69. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  70. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  71. GRB 260310A / AT2026fgk: LCO optical observations
  72. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  73. GRB 260317A: Fermi GBM Final Localization
  74. GRB 260316B: GECAM-B observation
  75. GRB 260316B: SVOM/GRM observation
  76. EP260316a: COLIBRÍ faint optical counterpart candidate
  77. Fermi-LAT Gamma-ray Observations of IceCube-260315A
  78. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  79. EP260316a: Xinglong optical upper limit
  80. GRB 260316B: Fermi GBM Final Real-time Localization
  81. EP260316a: optical upper limit with Kinder observations
  82. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  83. GRB 260314A: Glowbug gamma-ray detection
  84. IceCube-260315A: COLIBRÍ optical observations
  85. EP260314a: Xinglong optical upper limit
  86. EP260314a: optical upper limit with Kinder observations
  87. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  88. GRB 260310A / AT 2026fgk: iTelescope optical observations
  89. EP260314a: BOOTES-6/DPR optical upper limits at early times
  90. EP260314a: Global MASTER-Net observations report
  91. EP260314a: SVOM/VT optical candidate
  92. GRB 260314A: GECAM-B observation of a burst
  93. GRB 260310A / AT2026fgk: SAO RAS optical observations
  94. GRB 260310A/AT2026fgk: radio detection at 15GHz
  95. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  96. Fermi GRB 260313A: Global MASTER-Net observations report
  97. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  98. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  99. Swift BAT trigger 1500287: A solar flare
  100. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153

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