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"

22792 results found.

  1. GRB 260506B: AstroSat CZTI detection
  2. EP260507a: REM optical/NIR observations
  3. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  4. EP260507a: COLIBRÍ optical observations
  5. EP260507a: NOT optical observations
  6. EP260507a: further Liverpool Telescope observations
  7. EP260507a: Liverpool Telescope optical upper limits
  8. EP260507a: GOTO optical counterpart detection
  9. EP260507a: TRT optical counterpart detection
  10. EP260507a: Kinder optical counterpart candidate
  11. EP260507a: LCO optical counterpart
  12. EP260507a: Einstein Probe detection of an X-ray transient
  13. GRB 260503A: GECAM-B observation of a burst
  14. GRB 260430B: Glowbug gamma-ray detection
  15. GRB 260421B: radio observation with the VLA
  16. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  17. GRB 260502A: SVOM/GRM observation of a short GRB
  18. GRB 260503A: SVOM/GRM observation of a GRB
  19. GRB 260504B: REM optical/NIR observations
  20. IPN triangulation of GRB 260429A
  21. IPN triangulation of GRB 260428A
  22. GRB 260504B: LCO z-band upper limit
  23. SVOM GRB 260504B: MASTER-OAFA optical observations
  24. GRB 260504B: SVOM detection of a short burst
  25. GRB 260503A: Fermi GBM Final Real-time Localization
  26. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  27. IPN triangulation of a bright burst from SGR 1E1841-045
  28. GRB 260429B / EP260429a: AstroSat CZTI detection
  29. EP260502a: BOOTES-7: early optical upper limit
  30. EP260502a: Las Cumbres upper limit
  31. EP260502a: Einstein Probe detection of an X-ray transient
  32. GRB 260429A: SVOM/GRM observation of a short burst
  33. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  34. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  35. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  36. EP260429a: LCO optical upper limits
  37. EP260430a: LCO optical upper limits
  38. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  39. EP260430a: Einstein Probe detection of an X-ray transient
  40. EP260429a: EP-WXT detection of a fast X-ray transient
  41. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  42. GRB 260428A: AstroSat CZTI detection
  43. EP260416a: Mondy and Terskol optical upper limits
  44. GRB 260424B: Glowbug gamma-ray detection of a short burst
  45. GRB 260424B: COLIBRÍ optical upper limit
  46. Konus-Wind detection of GRB 260424B
  47. IPN triangulation of GRB 260424B (short)
  48. GRB 260401A: cubesat Avion detection
  49. GRB 260424A: AstroSat CZTI detection of a long burst
  50. EP260321a: Upper limits from ATCA radio observations
  51. GRB 260421B: Kilonova-Catcher optical afterglow detection
  52. EP260416a: Mondy optical observations
  53. GRB 260421B: 3.6m DOT optical observation
  54. EP260416a: ZTSh R band observations
  55. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  56. GRB 260421B: SVOM/GRM observation
  57. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  58. GOTO26djh/AT2026jpw: ATCA radio detection
  59. GRB 260421B: J-band upper limit with WINTER
  60. GRB 260421B: LCO optical counterpart detection
  61. GOTO26djh/AT2026jpw: radio detection at 15GHz
  62. GRB 260421B: SVOM/VT optical observations
  63. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  64. GRB 260310A: Late-time Chandra X-ray Detection
  65. EP260416a: 1.3m DFOT optical observation
  66. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  67. GRB 260421B: LCO optical afterglow confirmation
  68. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  69. GRB 260421B: TRT optical counterpart detection
  70. GRB 260421B: SVOM detection of a long burst
  71. EP260321a: VLA radio follow-up
  72. GRB 260412A: LCOGT Optical Upper Limits
  73. EP260416a: Optical follow-up observations with Kinder
  74. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  75. GRB 260417A: SVOM/GRM observation
  76. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  77. EP260417a: GROWTH-India Telescope optical upper limit
  78. EP260417b: GROWTH-India Telescope optical upper limit
  79. EP260416a: Ondrejov D50 optical detection
  80. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  81. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  82. EP260416a: GMG Optical Observation
  83. GRB 260417A: AstroSat CZTI detection
  84. IPN triangulation of GRB 260411B
  85. EP260416a: LCO observations confirm end of flaring phase
  86. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  87. EP260417a: TRT optical counterpart detection
  88. EP260417a: Einstein Probe detection of an X-ray transient
  89. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  90. EP260417b: Einstein Probe detection of a fast X-ray transient
  91. EP260416a: KAIT optical upper limit
  92. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  93. EP260416a: WFST optical observations and rebrightening
  94. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  95. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  96. GRB 260415B: Glowbug gamma-ray detection
  97. GRB 260411B: Glowbug gamma-ray detection
  98. GRB 260415A: Insight-HXMT/HE detection
  99. EP260416a: COLIBRÍ optical counterpart candidate
  100. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw

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