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"

31728 results found.

  1. EP260507a: TRT optical counterpart detection
  2. EP260507a: Kinder optical counterpart candidate
  3. EP260507a: LCO optical counterpart
  4. GRB 260504B: AstroSat CZTI detection
  5. GRB 260504B: SVOM/ECLAIRs refined analysis
  6. EP260502a is likely a flaring star
  7. Fermi GRB 260506A: Global MASTER-Net observations report
  8. GRB 260503A: GECAM-B observation of a burst
  9. GRB 260430B: Glowbug gamma-ray detection
  10. GRB 260504B: SVOM/VT optical upper limits
  11. GRB 260421B: radio observation with the VLA
  12. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  13. Konus-Wind detection of GRB 260504B (short/hard)
  14. GRB 260504B: GECAM-B detection
  15. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  16. GRB 260504B: SVOM/GRM spectral analysis
  17. GRB 260504B: SVOM/MXT refined analysis and potential detection
  18. GRB 260504B: EP-FXT upper limit
  19. GRB 260502A: SVOM/GRM observation of a short GRB
  20. GRB 260503A: SVOM/GRM observation of a GRB
  21. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  22. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  23. GRB 260504B: REM optical/NIR observations
  24. IPN triangulation of GRB 260429A
  25. IPN triangulation of GRB 260428A
  26. GRB 260504B: AST3-2 i-band upper limit
  27. GRB 260504B: LCO z-band upper limit
  28. SVOM GRB 260504B: MASTER-OAFA optical observations
  29. Fermi GRB 260504A: Global MASTER-Net observations report
  30. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  31. GRB 260502A: GECAM-B observation of a short burst
  32. IPN triangulation of a bright burst from SGR 1E1841-045
  33. GRB 260429B / EP260429a: EP-FXT follow-up observation
  34. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  35. GRB 260429B / EP260429a: AstroSat CZTI detection
  36. EP260502a: BOOTES-7: early optical upper limit
  37. EP260502a: Las Cumbres upper limit
  38. GRB 260429A: SVOM/GRM observation of a short burst
  39. EP260429a: Global MASTER-Net observations report
  40. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  41. GRB 260424B: AstroSat CZTI detection
  42. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  43. EP260429a: LCO optical upper limits
  44. EP260430a: LCO optical upper limits
  45. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  46. Fermi GRB 260429A: Global MASTER-Net observations report
  47. EP260430a: Global MASTER-Net observations report
  48. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  49. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  50. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  51. GRB 260428A: AstroSat CZTI detection
  52. Fermi GRB 260428A: Global MASTER-Net observations report
  53. EP260416a: Mondy and Terskol optical upper limits
  54. GRB 260424B: Glowbug gamma-ray detection of a short burst
  55. GRB 260424B: COLIBRÍ optical upper limit
  56. Konus-Wind detection of GRB 260424B
  57. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  58. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  59. IPN triangulation of GRB 260424B (short)
  60. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  61. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  62. GRB 260401A: cubesat Avion detection
  63. EP260321a: Upper limits from ATCA radio observations
  64. GRB 260421B: Kilonova-Catcher optical afterglow detection
  65. GRB 260421B: Insight-HXMT/HE detection
  66. The EP-WXT trigger 01709258652: Mondy optical observations
  67. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  68. EP260416a: Mondy optical observations
  69. GRB 260421B: SVOM/ECLAIRs refined analysis
  70. GRB 260421B: 3.6m DOT optical observation
  71. EP260416a: ZTSh R band observations
  72. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  73. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  74. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  75. GRB 260419A: AstroSat CZTI detection
  76. GRB 260421B: SVOM/GRM observation
  77. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  78. GRB 260421B: EP-FXT follow-up observation
  79. GOTO26djh/AT2026jpw: ATCA radio detection
  80. GRB 260421B: J-band upper limit with WINTER
  81. GRB 260421B: LCO optical counterpart detection
  82. GRB 260421B: Fermi GBM Observation
  83. GRB 260421A: AstroSat CZTI detection
  84. GOTO26djh/AT2026jpw: radio detection at 15GHz
  85. GRB 260412A: SVOM/ECLAIRs refined analysis
  86. GRB 260421B: SVOM/VT optical observations
  87. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  88. GRB 260310A: Late-time Chandra X-ray Detection
  89. GRB 260418A: Insight-HXMT/HE detection
  90. EP260416a: 1.3m DFOT optical observation
  91. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  92. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  93. Fermi GRB 260421C: Global MASTER-Net observations report
  94. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  95. Fermi GRB 260421B: Global MASTER-Net observations report
  96. GRB 260421B: BOOTES-7 early optical afterglow detection
  97. GRB 260421B: LCO optical afterglow confirmation
  98. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  99. GRB 260421B: TRT optical counterpart detection
  100. GRB 260421B: SVOM detection of a long burst

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