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"

26769 results found.

  1. The EP-WXT trigger 01709261576 is likely a flaring star
  2. GRB 260429B / EP260429a: EP-FXT follow-up observation
  3. EP260502a: BOOTES-7: early optical upper limit
  4. EP260502a: Las Cumbres upper limit
  5. GRB 260429A: SVOM/GRM observation of a short burst
  6. EP260429a: Global MASTER-Net observations report
  7. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  8. EP260429a: LCO optical upper limits
  9. EP260430a: LCO optical upper limits
  10. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  11. GRB 260429A: Fermi GBM Detection
  12. Fermi GRB 260429A: Global MASTER-Net observations report
  13. EP260430a: Global MASTER-Net observations report
  14. EP260430a: Einstein Probe detection of an X-ray transient
  15. GRB 260429A: Fermi GBM Final Real-time Localization
  16. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  17. Fermi GRB 260428A: Global MASTER-Net observations report
  18. GRB 260424B: COLIBRÍ optical upper limit
  19. GRB 260428A: Fermi GBM Final Real-time Localization
  20. GRB 260424C: Fermi GBM Final Localization
  21. GRB 260424B: SVOM/GRM detection of a short burst
  22. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  23. IceCube Alert 260425A: Global MASTER-Net observations report
  24. Fermi trigger No 798737427: Global MASTER-Net observations report
  25. The EP-WXT trigger 01709258652: Mondy optical observations
  26. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  27. GRB 260421B: SVOM/ECLAIRs refined analysis
  28. GRB 260421B: 3.6m DOT optical observation
  29. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  30. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  31. GRB 260421B: SVOM/GRM observation
  32. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  33. GRB 260421B: EP-FXT follow-up observation
  34. The EP-WXT trigger 01709260362 is likely a flaring star
  35. GRB 260421B: J-band upper limit with WINTER
  36. GRB 260421B: LCO optical counterpart detection
  37. GRB 260421B: Fermi GBM Observation
  38. Fermi Gamma-ray Burst Monitor trigger 798482368/260421694 is not a GRB
  39. GRB 260412A: SVOM/ECLAIRs refined analysis
  40. GRB 260421B: SVOM/VT optical observations
  41. EP260416a: J band upper limit by SYSU 80cm infrared telescope
  42. GRB 260310A: Late-time Chandra X-ray Detection
  43. EP260416a: 1.3m DFOT optical observation
  44. Fermi GRB 260421C: Global MASTER-Net observations report
  45. GRB 260421C: Fermi GBM Final Real-time Localization
  46. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  47. Fermi GRB 260421B: Global MASTER-Net observations report
  48. GRB 260421B: LCO optical afterglow confirmation
  49. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  50. GRB 260421B: SVOM detection of a long burst
  51. GRB 260421B: BALROG localization (Fermi Trigger 798437606 / GRB 260421176)
  52. GRB 260421B: Fermi GBM Final Real-time Localization
  53. Fermi GRB 260421A: Global MASTER-Net observations report
  54. GRB 260421A: Fermi GBM Final Real-time Localization
  55. EP260321a: VLA radio follow-up
  56. GRB 260412A: LCOGT Optical Upper Limits
  57. The EP-WXT trigger 01709260314 is likely a flaring star
  58. EP-WXT trigger 01709260303: KAIT optical observations
  59. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  60. The EP-WXT trigger 01709260303 is likely a flaring star
  61. EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
  62. GRB 260419B: Fermi GBM Final Real-time Localization
  63. GRB 260419A: Fermi GBM Final Real-time Localization
  64. Fermi trigger No 798275385: Global MASTER-Net observations report
  65. EP260417a: GROWTH-India Telescope optical upper limit
  66. Fermi GRB 260417B: Global MASTER-Net observations report
  67. EP260417b: GROWTH-India Telescope optical upper limit
  68. EP260416a: Ondrejov D50 optical detection
  69. GRB 260418B: Fermi GBM Final Real-time Localization
  70. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  71. EP260417a: Global MASTER-Net observations report
  72. GRB 260418A: Fermi GBM Final Real-time Localization
  73. EP260416a: GMG Optical Observation
  74. Fermi GRB 260417A: Global MASTER-Net observations report
  75. GRB 260417B: Fermi GBM Final Real-time Localization
  76. EP260416a: LCO observations confirm end of flaring phase
  77. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  78. EP260417a: TRT optical counterpart detection
  79. EP-WXT trigger 01709259586: KAIT optical observations
  80. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  81. EP260416a: WFST optical observations and rebrightening
  82. GRB 260417A: Fermi GBM Final Real-time Localization
  83. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  84. GRB 260415B: Glowbug gamma-ray detection
  85. EP260416a: COLIBRÍ optical counterpart candidate
  86. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  87. EP260416a: Global MASTER-Net observations report
  88. GRB 260415B: NuSTAR detection of long prompt emission
  89. GRB 260415B: Fermi GBM Final Localization
  90. GRB 260415A: Fermi GBM Final Real-time Localization
  91. Fermi trigger No 797912738: Global MASTER-Net observations report
  92. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  93. GRB 260414A: Fermi GBM Final Real-time Localization
  94. The EP-WXT trigger 01709260122 is likely a flaring star
  95. Fermi GRB 260413A: Global MASTER-Net observations report
  96. GRB 260413A: Fermi GBM Final Real-time Localization
  97. EP260321a: SVOM/VT optical observations and color changes around peak
  98. The EP-WXT trigger 01709260010 is likely a flaring star
  99. Fermi GRB 260412A: Global MASTER-Net observations report
  100. GRB 260412A: Fermi GBM Observation

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