Skip to main content
New! MAXI Notices and Schema v7.2.0. 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. EP260602c: Einstein Probe detection of a fast X-ray transient
  2. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  3. EP260602a: COLIBRÍ optical observations
  4. GRB260601B/EP260601a: NOT near-infrared observations
  5. SVOM GRB260603.23: Global MASTER-Net observations report
  6. GRB 260603A: SVOM detection of a burst
  7. EP260602b: Einstein Probe detection of a fast X-ray transient
  8. GRB 260601B/EP260601a: Insight-HXMT detection
  9. Fermi GRB 260602B: Global MASTER-Net observations report
  10. Fermi GRB 260602B: Global MASTER-Net observations report
  11. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  12. EP260602a: SVOM/VT optical candidate
  13. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  14. GRB 260602B: Fermi GBM Final Localization
  15. GRB 260601A: GECAM-B observation of a short burst
  16. GRB 260601B/EP260601a: J-band upper limit with WINTER
  17. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  18. EP260530a/AT 2026nwl: KAIT optical observations
  19. GRB 260602A: Fermi GBM Final Real-time Localization
  20. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  21. EP260602a: Optical upper limits with Kinder observations
  22. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  23. EP260602a: Einstein Probe detection of a fast X-ray transient
  24. GRB 260601B/EP260601a: SVOM/VT optical observations
  25. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  26. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  27. EP260601a: Einstein Probe detection of an X-ray transient
  28. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  29. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  30. GRB 260601A: Glowbug gamma-ray detection of a short burst
  31. GRB 260531B: Glowbug gamma-ray detection
  32. GRB 260516D: VLA radio detection
  33. GRB 260601A: Fermi GBM Observation
  34. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  35. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  36. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  37. Fermi GRB 260601A: Global MASTER-Net observations report
  38. GRB 260601A: Fermi GBM Final Real-time Localization
  39. GRB 260531B: GECAM-B observation
  40. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  41. The EP-WXT trigger 01709266272 is likely a flaring star
  42. GRB 260531C: Fermi GBM Final Localization Correction
  43. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  44. AT2026nik: EP-FXT X-ray counterpart
  45. Fermi trigger No 801900520: Global MASTER-Net observations report
  46. GRB 260531B: Fermi GBM Final Real-time Localization
  47. GRB 260531A: MAXI/GSC detection
  48. AT 2026nuz: COLIBRÍ optical observations
  49. IPN triangulation of GRB 260527A / EP260527a
  50. EP260527a/GRB 260527A: further FTW optical and NIR observations
  51. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  52. GRB 260530A: Fermi GBM Final Real-time Localization
  53. GRB 260527A / EP260527a: VLA radio detection
  54. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  55. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  56. GRB 260529A: GOTO tentative optical afterglow candidate
  57. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  58. GRB 260527A/EP260527a: Insight-HXMT detection
  59. Fermi GRB 260529A: Global MASTER-Net observations report
  60. GRB 260529A: Fermi GBM Final Real-time Localization
  61. EP260526a: SVOM/VT optical upper limits
  62. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  63. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  64. EP260527a / GRB 260527A: NOT optical observations
  65. GRB 260527A/EP260527a: FTW optical and NIR observations
  66. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  67. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  68. EP260527a/GRB 260527A: EP-FXT follow-up observation
  69. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  70. GRB 260526A: GECAM-B observation
  71. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  72. EP260526a: EP-FXT follow-up observation
  73. EP260527a: SVOM/VT optical observation
  74. EP260527a: COLIBRÍ optical detection
  75. EP260527a: Einstein Probe detection of a fast X-ray transient
  76. The EP-WXT trigger 01709266172 is likely a flaring star
  77. The EP-WXT trigger 01709266147 is likely a flaring star
  78. Fermi trigger No 801580882: Global MASTER-Net observations report
  79. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  80. EP260526a: LCO optical upper limits
  81. EP260526a: Einstein Probe detection of a fast X-ray transient
  82. GRB 260525A: AstroSat CZTI detection
  83. EP260526.405: COLIBRÍ optical upper limits
  84. The EP-WXT trigger 01709266106 is not a real source
  85. Fermi GRB 260526A: Global MASTER-Net observations report
  86. GRB 260526A: Fermi GBM Final Real-time Localization
  87. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  88. EP-WXT 01709266106: NOT optical upper limits
  89. Fermi GRB 260525A: Global MASTER-Net observations report
  90. GRB 260525A: Fermi GBM Final Real-time Localization
  91. GRB 260523B: AstroSat CZTI detection
  92. GRB 260523B: GECAM-B observation
  93. Fermi GRB 260523A: Global MASTER-Net observations report
  94. GRB 260523B: Fermi GBM Final Real-time Localization
  95. GRB 260523A: Fermi GBM Final Real-time Localization
  96. GRB 260522A: Fermi GBM Observation
  97. GRB 260522B: NuSTAR detection of prompt emission
  98. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  99. GRB 260522B: Fermi GBM Final Real-time Localization
  100. GRB 260522A: GOTO optical upper limit

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