Skip to main content
New JavaScript client! 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. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  2. EP260530a/AT 2026nwl: KAIT optical observations
  3. GRB 260602A: Fermi GBM Final Real-time Localization
  4. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  5. EP260602a: Optical upper limits with Kinder observations
  6. GRB 260601B / EP260601a: NuSTAR detection of prompt emission
  7. EP260602a: Einstein Probe detection of a fast X-ray transient
  8. GRB 260601B/EP260601a: SVOM/VT optical observations
  9. GRB 260601B/EP260601a: GECAM-B analysis suggests a possible long duration Type I burst
  10. GRB 260601B: GECAM-B detection of a burst probably associated with EP260601a
  11. EP260601a: Einstein Probe detection of an X-ray transient
  12. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  13. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  14. GRB 260601A: Glowbug gamma-ray detection of a short burst
  15. GRB 260531B: Glowbug gamma-ray detection
  16. GRB 260516D: VLA radio detection
  17. GRB 260601A: Fermi GBM Observation
  18. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  19. GRB 260530C: SVOM/ECLAIRs detection of a burst through on-ground search
  20. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  21. Fermi GRB 260601A: Global MASTER-Net observations report
  22. GRB 260601A: Fermi GBM Final Real-time Localization
  23. GRB 260531B: GECAM-B observation
  24. GRB 260518B: SVOM/ECLAIRs detection of a soft burst possibly associated with EP 260518a and AT 2026ndp
  25. The EP-WXT trigger 01709266272 is likely a flaring star
  26. GRB 260531C: Fermi GBM Final Localization Correction
  27. Fermi Gamma-ray Burst Monitor trigger 801900520/260531256 is not a GRB
  28. AT2026nik: EP-FXT X-ray counterpart
  29. Fermi trigger No 801900520: Global MASTER-Net observations report
  30. GRB 260531B: Fermi GBM Final Real-time Localization
  31. GRB 260531A: MAXI/GSC detection
  32. AT 2026nuz: COLIBRÍ optical observations
  33. IPN triangulation of GRB 260527A / EP260527a
  34. EP260527a/GRB 260527A: further FTW optical and NIR observations
  35. GRB 260530B: SVOM/GRM detection of a possible bright short GRB
  36. GRB 260530A: Fermi GBM Final Real-time Localization
  37. GRB 260527A / EP260527a: VLA radio detection
  38. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  39. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  40. GRB 260529A: GOTO tentative optical afterglow candidate
  41. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  42. GRB 260527A/EP260527a: Insight-HXMT detection
  43. Fermi GRB 260529A: Global MASTER-Net observations report
  44. GRB 260529A: Fermi GBM Final Real-time Localization
  45. EP260526a: SVOM/VT optical upper limits
  46. GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
  47. EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
  48. EP260527a / GRB 260527A: NOT optical observations
  49. GRB 260527A/EP260527a: FTW optical and NIR observations
  50. EP260527a/GRB 260527A: Infrared J upper limit with MDM/MIRAGE
  51. GRB 260527A: CALET Gamma-Ray Burst Monitor detection
  52. EP260527a/GRB 260527A: EP-FXT follow-up observation
  53. GRB 260527A: GECAM-B detection of a short burst probably associated with EP260527a
  54. GRB 260526A: GECAM-B observation
  55. Konus-Wind detection of GRB 260527A (short/hard) ~4 min before EP260527a
  56. EP260526a: EP-FXT follow-up observation
  57. EP260527a: SVOM/VT optical observation
  58. EP260527a: COLIBRÍ optical detection
  59. EP260527a: Einstein Probe detection of a fast X-ray transient
  60. The EP-WXT trigger 01709266172 is likely a flaring star
  61. The EP-WXT trigger 01709266147 is likely a flaring star
  62. Fermi trigger No 801580882: Global MASTER-Net observations report
  63. GRB 260524A: SVOM/ECLAIRs detection of a burst through on-ground search
  64. EP260526a: LCO optical upper limits
  65. EP260526a: Einstein Probe detection of a fast X-ray transient
  66. GRB 260525A: AstroSat CZTI detection
  67. EP260526.405: COLIBRÍ optical upper limits
  68. The EP-WXT trigger 01709266106 is not a real source
  69. Fermi GRB 260526A: Global MASTER-Net observations report
  70. GRB 260526A: Fermi GBM Final Real-time Localization
  71. EP01709266106 (EP260526a?): Liverpool Telescope upper limits
  72. EP-WXT 01709266106: NOT optical upper limits
  73. Fermi GRB 260525A: Global MASTER-Net observations report
  74. GRB 260525A: Fermi GBM Final Real-time Localization
  75. GRB 260523B: AstroSat CZTI detection
  76. GRB 260523B: GECAM-B observation
  77. Fermi GRB 260523A: Global MASTER-Net observations report
  78. GRB 260523B: Fermi GBM Final Real-time Localization
  79. GRB 260523A: Fermi GBM Final Real-time Localization
  80. GRB 260522A: Fermi GBM Observation
  81. GRB 260522B: NuSTAR detection of prompt emission
  82. EP260518a (AT2026ndp): LCO observations and Gemini-South Redshift z = 2.28
  83. GRB 260522B: Fermi GBM Final Real-time Localization
  84. GRB 260522A: GOTO optical upper limit
  85. Fermi trigger No 801135305: Global MASTER-Net observations report
  86. Fermi GRB 260522A: Global MASTER-Net observations report
  87. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  88. GRB 260522A: Fermi-LAT detection
  89. GRB 260519C: SVOM/GRM observation
  90. GRB 260522A: Fermi GBM Final Real-time Localization
  91. GRB 260511A: iTelescope T-75 optical detection
  92. GRB 260520B: SVOM/GRM observation
  93. GRB 260411B: TERI Gamma-ray detection
  94. GRB 260407A: TERI Gamma-ray detection
  95. GRB 260307A: TERI Gamma-ray detection
  96. GRB 260225D: TERI Gamma-ray detection
  97. GRB 251118A: TERI Gamma-ray detection
  98. GRB 251113A: TERI Gamma-ray detection
  99. GRB 260428A: TERI Gamma-ray detection
  100. Konus-Wind detection of GRB 260519C

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