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"

22056 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: Kinder optical counterpart candidate
  6. GRB 260504B: SVOM/ECLAIRs refined analysis
  7. EP260502a is likely a flaring star
  8. Fermi GRB 260506A: Global MASTER-Net observations report
  9. IceCube Alert 260505A: Global MASTER-Net observations report
  10. GRB 260504B: SVOM/VT optical upper limits
  11. GRB 260421B: radio observation with the VLA
  12. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  13. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  14. GRB 260504B: REM optical/NIR observations
  15. GRB 260504B: AST3-2 i-band upper limit
  16. SVOM GRB 260504B: MASTER-OAFA optical observations
  17. Fermi GRB 260504A: Global MASTER-Net observations report
  18. GRB 260429B / EP260429a: EP-FXT follow-up observation
  19. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  20. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  21. EP260429a: Global MASTER-Net observations report
  22. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  23. Fermi GRB 260429A: Global MASTER-Net observations report
  24. EP260430a: Global MASTER-Net observations report
  25. Fermi GRB 260428A: Global MASTER-Net observations report
  26. GRB 260424B: COLIBRÍ optical upper limit
  27. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  28. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  29. IceCube Alert 260425A: Global MASTER-Net observations report
  30. Fermi trigger No 798737427: Global MASTER-Net observations report
  31. EP260321a: Upper limits from ATCA radio observations
  32. GRB 260421B: Kilonova-Catcher optical afterglow detection
  33. The EP-WXT trigger 01709258652: Mondy optical observations
  34. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  35. EP260416a: Mondy optical observations
  36. GRB 260421B: SVOM/ECLAIRs refined analysis
  37. GRB 260421B: 3.6m DOT optical observation
  38. EP260416a: ZTSh R band observations
  39. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  40. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  41. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  42. GOTO26djh/AT2026jpw: ATCA radio detection
  43. GRB 260421B: J-band upper limit with WINTER
  44. GRB 260421B: LCO optical counterpart detection
  45. GOTO26djh/AT2026jpw: radio detection at 15GHz
  46. GRB 260412A: SVOM/ECLAIRs refined analysis
  47. GRB 260421B: SVOM/VT optical observations
  48. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  49. GRB 260310A: Late-time Chandra X-ray Detection
  50. EP260416a: 1.3m DFOT optical observation
  51. Fermi GRB 260421C: Global MASTER-Net observations report
  52. Fermi GRB 260421B: Global MASTER-Net observations report
  53. GRB 260421B: LCO optical afterglow confirmation
  54. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  55. Fermi GRB 260421A: Global MASTER-Net observations report
  56. EP260321a: VLA radio follow-up
  57. EP260416a: Optical follow-up observations with Kinder
  58. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  59. EP-WXT trigger 01709260303: KAIT optical observations
  60. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  61. Fermi trigger No 798275385: Global MASTER-Net observations report
  62. Fermi GRB 260417B: Global MASTER-Net observations report
  63. EP260416a: Ondrejov D50 optical detection
  64. EP260417a: Global MASTER-Net observations report
  65. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  66. EP260416a: NOT tentative spectroscopic redshift of z =1.909
  67. Fermi GRB 260417A: Global MASTER-Net observations report
  68. Konus-Wind detection of GRB 260411B
  69. EP260416a: LCO observations confirm end of flaring phase
  70. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  71. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  72. EP-WXT trigger 01709259586: KAIT optical observations
  73. EP260416a: WFST optical observations and rebrightening
  74. GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
  75. GRB 260411B: Glowbug gamma-ray detection
  76. EP260416a: COLIBRÍ optical counterpart candidate
  77. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  78. EP260416a: Global MASTER-Net observations report
  79. GOTO26djh/AT2026jpw : MASTER OT observation
  80. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  81. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  82. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  83. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  84. Fermi trigger No 797912738: Global MASTER-Net observations report
  85. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  86. EP260321a: CMO SAI J,K observations
  87. Fermi GRB 260413A: Global MASTER-Net observations report
  88. EP260321a: SVOM/VT optical observations and color changes around peak
  89. Fermi GRB 260412A: Global MASTER-Net observations report
  90. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  91. GRB 260411B: COLIBRÍ optical observations
  92. GRB 260411B: Ondrejov D50 optical afterglow detection
  93. GRB260411B: 3.6m DOT optical observation
  94. GRB 260411B: GOTO optical counterpart candidate
  95. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  96. EP-WXT01709259790: Optical Upper limits with kinder observations
  97. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  98. EP260321a: Chandra X-ray Non-detection
  99. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  100. EP260409a: SVOM/VT optical upper limits

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