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"

27246 results found.

  1. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  2. GRB 260509A: SVOM/VT optical candidate with VHF data
  3. GRB 260509A: LCO optical counterpart detection
  4. GRB 260509A: SVOM detection of a burst
  5. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  6. EP260507a: REM optical/NIR observations
  7. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  8. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  9. EP260507a: COLIBRÍ optical observations
  10. EP260507a: NOT optical observations
  11. EP260507a: further Liverpool Telescope observations
  12. EP260507a: Liverpool Telescope optical upper limits
  13. EP260507a: TRT optical counterpart detection
  14. EP260507a: Kinder optical counterpart candidate
  15. EP260507a: LCO optical counterpart
  16. EP260507a: Einstein Probe detection of an X-ray transient
  17. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  18. Fermi GRB 260506A: Global MASTER-Net observations report
  19. IceCube Alert 260505A: Global MASTER-Net observations report
  20. GRB 260430B: Glowbug gamma-ray detection
  21. GRB 260421B: radio observation with the VLA
  22. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  23. GRB 260430B: AstroSat CZTI detection of a long burst
  24. GRB 260502A: SVOM/GRM observation of a short GRB
  25. GRB 260503A: SVOM/GRM observation of a GRB
  26. Konus-Wind detection of GRB 260411C
  27. GRB 260504B: REM optical/NIR observations
  28. GRB 260504B: LCO z-band upper limit
  29. SVOM GRB 260504B: MASTER-OAFA optical observations
  30. GRB 260504B: SVOM detection of a short burst
  31. Fermi GRB 260504A: Global MASTER-Net observations report
  32. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  33. GRB 260429B / EP260429a: EP-FXT follow-up observation
  34. EP260502a: Einstein Probe detection of an X-ray transient
  35. GRB 260429A: SVOM/GRM observation of a short burst
  36. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  37. EP260429a: Global MASTER-Net observations report
  38. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  39. GRB 260424B: AstroSat CZTI detection
  40. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  41. EP260429a: LCO optical upper limits
  42. EP260430a: LCO optical upper limits
  43. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  44. GRB 260429A: Fermi GBM Detection
  45. Fermi GRB 260429A: Global MASTER-Net observations report
  46. EP260430a: Global MASTER-Net observations report
  47. EP260430a: Einstein Probe detection of an X-ray transient
  48. EP260429a: EP-WXT detection of a fast X-ray transient
  49. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  50. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  51. Fermi GRB 260428A: Global MASTER-Net observations report
  52. EP260416a: Mondy and Terskol optical upper limits
  53. GRB 260424B: Glowbug gamma-ray detection of a short burst
  54. GRB 260424B: COLIBRÍ optical upper limit
  55. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  56. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  57. IceCube Alert 260425A: Global MASTER-Net observations report
  58. Fermi trigger No 798737427: Global MASTER-Net observations report
  59. GRB 260401A: cubesat Avion detection
  60. EP260321a: Upper limits from ATCA radio observations
  61. GRB 260421B: Kilonova-Catcher optical afterglow detection
  62. The EP-WXT trigger 01709258652: Mondy optical observations
  63. EP260416a: Mondy optical observations
  64. GRB 260421B: 3.6m DOT optical observation
  65. EP260416a: ZTSh R band observations
  66. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  67. GRB 260421B: SVOM/GRM observation
  68. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  69. GRB 260421B: EP-FXT follow-up observation
  70. GOTO26djh/AT2026jpw: ATCA radio detection
  71. GRB 260421B: J-band upper limit with WINTER
  72. GRB 260421B: LCO optical counterpart detection
  73. GRB 260421B: Fermi GBM Observation
  74. GOTO26djh/AT2026jpw: radio detection at 15GHz
  75. GRB 260421B: SVOM/VT optical observations
  76. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  77. GRB 260310A: Late-time Chandra X-ray Detection
  78. EP260416a: 1.3m DFOT optical observation
  79. Fermi GRB 260421C: Global MASTER-Net observations report
  80. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  81. Fermi GRB 260421B: Global MASTER-Net observations report
  82. GRB 260421B: LCO optical afterglow confirmation
  83. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  84. GRB 260421B: TRT optical counterpart detection
  85. GRB 260421B: SVOM detection of a long burst
  86. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  87. Fermi GRB 260421A: Global MASTER-Net observations report
  88. EP260321a: VLA radio follow-up
  89. GRB 260412A: LCOGT Optical Upper Limits
  90. EP260416a: Optical follow-up observations with Kinder
  91. GOTO26djh/AT2026jpw: CrAO and Mondy optical observations of the transient
  92. GRB 260417A: SVOM/GRM observation
  93. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  94. Fermi trigger No 798275385: Global MASTER-Net observations report
  95. EP260417a: GROWTH-India Telescope optical upper limit
  96. Fermi GRB 260417B: Global MASTER-Net observations report
  97. EP260417b: GROWTH-India Telescope optical upper limit
  98. EP260416a: Ondrejov D50 optical detection
  99. EP260417a: Global MASTER-Net observations report
  100. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations

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