Skip to main content
New! CHIME and DSA-110 FRB Notices, IceCube Notices and Schema v6.1.1. 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"

5409 results found.

  1. EP260131a: SVOM/VT optical observation
  2. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  3. GRB 260131B: MAXI/GSC detection
  4. Fermi GRB 260127A: Global MASTER-Net observations report
  5. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  6. GRB 260127A: COLIBRÍ optical observations
  7. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  8. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  9. GRB 260122A: Fermi GBM Final Real-time Localization
  10. Fermi GRB 260120C: Global MASTER-Net observations report
  11. SVOM GRB260121.06: Global MASTER-Net observations report
  12. SVOM GRB260119.90: Global MASTER-Net observations report
  13. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  14. EP260119a: Global MASTER-Net observations report
  15. EP260119a: LCO optical observations
  16. EP260119a: COLIBRÍ optical counterpart candidate
  17. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  18. Fermi-LAT Gamma-ray Observations of IceCube-260111A
  19. The EP-WXT trigger 01709251266 is likely a flaring star
  20. Swift trigger 1436759 is not an astrophysical event
  21. GRB 260109C: LCO optical upper limits
  22. Fermi GRB 260105A: Global MASTER-Net observations report
  23. EP260104a: FTW optical observations
  24. EP260104a: Global MASTER-Net observations report
  25. EP260105a: Global MASTER-Net observations report
  26. SVOM GRB260103.08: Global MASTER-Net observations report
  27. Fermi GBM Sub-Threshold Detection of GRB 260102A
  28. GRB 260102A: SVOM detection of a burst
  29. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  30. EP251229a: Global MASTER-Net observations report
  31. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  32. Fermi GRB 251228A: Global MASTER-Net observations report
  33. SVOM GRB251227.07: Global MASTER-Net observations report
  34. EP251222a: FTW optical and NIR observations
  35. EP251222a: Global MASTER-Net observations report
  36. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  37. EP 251220a: COLIBRÍ detection of the optical counterpart
  38. EP251220a: Global MASTER-Net observations report
  39. Fermi-LAT Gamma-ray Observations of IceCube-251218A
  40. GRB 251220A: MAXI/GSC detection
  41. GRB 251216A: Fermi GBM Final Real-time Localization
  42. Fermi GRB 251215A: Global MASTER-Net observations report
  43. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  44. GRB 251214B: Swift-BAT refined analysis
  45. GRB 251214B: Fermi GBM Observation
  46. GRB 251214B: Swift/UVOT Detection
  47. GRB 251214B: Enhanced Swift-XRT position
  48. GRB 251214C: Fermi GBM Final Localization
  49. EP251214a: COLIBRÍ optical upper limit
  50. GRB 251214B: Swift detection of a burst with an optical counterpart
  51. GRB 251214B: Fermi GBM Final Real-time Localization
  52. Fermi GRB 251214A: Global MASTER-Net observations report
  53. EP251212a: KAIT optical upper limit
  54. EP251212a: EP-FXT follow-up observation
  55. GRB 251209A: NuSTAR detection of prompt emission
  56. IceCube-251210A: Upper limits from a search for additional neutrino events in IceCube
  57. GRB 251205A: 1.3m DFOT optical upper limit
  58. GRB 251209A: AstroSat CZTI detection
  59. GRB 251208A: AstroSat CZTI detection
  60. GRB 251208A: Glowbug gamma-ray detection
  61. GRB 251208B: COLIBRÍ optical upper limits
  62. Fermi GRB 251209A: Global MASTER-Net observations report
  63. Fermi GRB 251208C: Global MASTER-Net observations report
  64. GRB 251206A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  65. LAT GRB251208.43: Global MASTER-Net observations report
  66. GRB 251208A: Fermi GBM Final Real-time Localization
  67. EP-WXT trigger 01709249380: KAIT confirmation of a stellar flare
  68. GRB 251205A: Swift detection of a burst with an optical afterglow
  69. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  70. GRB 251129B: Glowbug gamma-ray detection of a short burst
  71. GRB 251203B: Swift-XRT observations
  72. GRB 251203B: SVOM/VT optical observation
  73. GRB 251203B: SVOM detection of a burst
  74. IPN triangulation of GRB 251129B (short/hard)
  75. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  76. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  77. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  78. GRB 251201B: Swift detection of a burst with an optical counterpart
  79. Fermi GRB 251130B: Global MASTER-Net observations report
  80. IceCube Alert 251130.75: Global MASTER-Net observations report
  81. EP251130a: COLIBRÍ optical counterpart candidate
  82. EP251129a/GRB 251129A: EP-FXT follow-up observations
  83. EP251129a: Global MASTER-Net observations report
  84. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  85. Fermi GRB 251125A: Global MASTER-Net observations report
  86. GRB 251122A / EP251122a: EP-FXT counterpart detection
  87. EP251118a: Continued Optical Detection with Kinder observations
  88. EP251118a: Global MASTER-Net observations report
  89. LAT GRB251118.86: Global MASTER-Net observations report
  90. GRB 251115A: Swift-XRT observations
  91. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  92. SVOM GRB251116C: Global MASTER-Net observations report
  93. Fermi GRB 251115A: Global MASTER-Net observations report
  94. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  95. GRB 251112A: Swift-BAT refined analysis
  96. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  97. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  98. Fermi Gamma-ray Burst Monitor trigger 784717756/251113381 is not a GRB
  99. GRB 251112A: Swift-XRT refined Analysis
  100. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq

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