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"

32532 results found.

  1. EP260507a: NOT optical observations
  2. EP260507a: further Liverpool Telescope observations
  3. EP260507a: Liverpool Telescope optical upper limits
  4. EP260507a: GOTO optical counterpart detection
  5. EP260507a: TRT optical counterpart detection
  6. EP260507a: Kinder optical counterpart candidate
  7. EP260507a: LCO optical counterpart
  8. GRB 260504B: AstroSat CZTI detection
  9. GRB 260504B: SVOM/ECLAIRs refined analysis
  10. EP260502a is likely a flaring star
  11. Fermi GRB 260506A: Global MASTER-Net observations report
  12. GRB 260503A: GECAM-B observation of a burst
  13. GRB 260430B: Glowbug gamma-ray detection
  14. GRB 260504B: SVOM/VT optical upper limits
  15. GRB 260421B: radio observation with the VLA
  16. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  17. Konus-Wind detection of GRB 260504B (short/hard)
  18. GRB 260504B: GECAM-B detection
  19. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  20. GRB 260504B: SVOM/GRM spectral analysis
  21. GRB 260504B: SVOM/MXT refined analysis and potential detection
  22. GRB 260504B: EP-FXT upper limit
  23. GRB 260502A: SVOM/GRM observation of a short GRB
  24. GRB 260503A: SVOM/GRM observation of a GRB
  25. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  26. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  27. GRB 260504B: REM optical/NIR observations
  28. IPN triangulation of GRB 260429A
  29. IPN triangulation of GRB 260428A
  30. GRB 260504B: AST3-2 i-band upper limit
  31. GRB 260504B: LCO z-band upper limit
  32. SVOM GRB 260504B: MASTER-OAFA optical observations
  33. Fermi GRB 260504A: Global MASTER-Net observations report
  34. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  35. GRB 260502A: GECAM-B observation of a short burst
  36. IPN triangulation of a bright burst from SGR 1E1841-045
  37. GRB 260429B / EP260429a: EP-FXT follow-up observation
  38. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  39. GRB 260429B / EP260429a: AstroSat CZTI detection
  40. EP260502a: BOOTES-7: early optical upper limit
  41. EP260502a: Las Cumbres upper limit
  42. GRB 260429A: SVOM/GRM observation of a short burst
  43. EP260429a: Global MASTER-Net observations report
  44. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  45. GRB 260424B: AstroSat CZTI detection
  46. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  47. EP260429a: LCO optical upper limits
  48. EP260430a: LCO optical upper limits
  49. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  50. Fermi GRB 260429A: Global MASTER-Net observations report
  51. EP260430a: Global MASTER-Net observations report
  52. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  53. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  54. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  55. GRB 260428A: AstroSat CZTI detection
  56. Fermi GRB 260428A: Global MASTER-Net observations report
  57. EP260416a: Mondy and Terskol optical upper limits
  58. GRB 260424B: Glowbug gamma-ray detection of a short burst
  59. GRB 260424B: COLIBRÍ optical upper limit
  60. Konus-Wind detection of GRB 260424B
  61. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  62. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  63. IPN triangulation of GRB 260424B (short)
  64. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  65. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  66. GRB 260401A: cubesat Avion detection
  67. EP260321a: Upper limits from ATCA radio observations
  68. GRB 260421B: Kilonova-Catcher optical afterglow detection
  69. GRB 260421B: Insight-HXMT/HE detection
  70. The EP-WXT trigger 01709258652: Mondy optical observations
  71. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  72. EP260416a: Mondy optical observations
  73. GRB 260421B: SVOM/ECLAIRs refined analysis
  74. GRB 260421B: 3.6m DOT optical observation
  75. EP260416a: ZTSh R band observations
  76. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  77. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  78. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  79. GRB 260419A: AstroSat CZTI detection
  80. GRB 260421B: SVOM/GRM observation
  81. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  82. GRB 260421B: EP-FXT follow-up observation
  83. GOTO26djh/AT2026jpw: ATCA radio detection
  84. GRB 260421B: J-band upper limit with WINTER
  85. GRB 260421B: LCO optical counterpart detection
  86. GRB 260421B: Fermi GBM Observation
  87. GRB 260421A: AstroSat CZTI detection
  88. GOTO26djh/AT2026jpw: radio detection at 15GHz
  89. GRB 260412A: SVOM/ECLAIRs refined analysis
  90. GRB 260421B: SVOM/VT optical observations
  91. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  92. GRB 260310A: Late-time Chandra X-ray Detection
  93. GRB 260418A: Insight-HXMT/HE detection
  94. EP260416a: 1.3m DFOT optical observation
  95. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  96. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  97. Fermi GRB 260421C: Global MASTER-Net observations report
  98. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  99. Fermi GRB 260421B: Global MASTER-Net observations report
  100. GRB 260421B: BOOTES-7 early optical afterglow detection

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
Looking for U.S. government information and services? Visit USA.gov